Earlier this month, NASA’s TESS space telescope successfully captured the faint glow and tail of an interstellar comet, further enriching its archive with observations that may provide critical insights into this unique celestial visitor from beyond our solar system.
This 3I/ATLAS image was captured by NASA’s TESS satellite on January 15, 2026. Image credit: NASA/Daniel Muthukrishna, MIT.
The interstellar comet 3I/ATLAS was discovered on July 1, 2025, by the NASA-funded ATLAS survey telescope in Rio Hurtado, Chile.
Known as C/2025 N1 (ATLAS) and A11pl3Z, this comet originated from the Sagittarius constellation.
3I/ATLAS holds the record for the most dynamically extreme orbit of any object tracked in our solar system.
It reached its closest approach to the Sun, or perihelion, on October 30, 2025.
The comet passed within 1.4 astronomical units (approximately 210 million km) of our Sun, just crossing Mars’ orbit.
After its brief obscuration behind the Sun, it reemerged near the triple star system Zania, located in the Virgo constellation.
According to MIT astronomer Daniel Muthukrishna and his team, “The TESS spacecraft systematically scans vast areas of the sky for about a month, looking for variations in light from distant stars to identify orbiting exoplanets and new worlds beyond our solar system.”
“Additionally, this technology enables TESS to detect and monitor remote comets and asteroids,” they added.
Notably, 3I/ATLAS had been observed prior to its official discovery in May 2025. For more details, you can read the findings.
From January 15 to 22, 2026, TESS re-observed the interstellar comet during a dedicated observation period.
The comet’s brightness measured approximately 11.5 times the apparent magnitude, making it about 100 times dimmer than what the human eye can perceive.
By revisiting the TESS data, astronomers successfully identified this faint comet by stacking multiple observations to track its motion, showcasing the extraordinary capabilities of the TESS mission.
On January 22, 2026, the NASA/ESA Hubble Space Telescope captured stunning images of interstellar comet 3I/ATLAS, showing it in near-perfect alignment with the Sun-Earth axis. This observation unveiled an unprecedented jet structure and an elongated tail.
This image of interstellar comet 3I/ATLAS was captured by Hubble’s WFC3 instrument on January 22, 2026, at 13:10 UTC. Image credit: NASA / ESA / Hubble / Man Tu Hui, Shanghai Observatory.
According to researchers Professor Abraham Loeb from Harvard University and Dr. Mauro Barbieri from the INAF Padua Observatory, interstellar objects like 3I/ATLAS provide a rare opportunity to study materials from distant star systems. They detailed their findings in recent papers published in American Astronomical Society Research Notes.
Previous interstellar visitors such as 1I/Oumuamua lacked evidence of gas or dust, while 2I/Borisov was only observed at angles greater than 16 degrees from the Sun-Earth alignment, missing the chance for detailed study.
On January 22, 2026, comet 3I/ATLAS was positioned at an astonishingly small angle of just 0.69 degrees relative to the Earth-Sun axis, allowing for an optimal view as our planet passed nearly directly between the Sun and the comet.
This rare alignment caused a significant brightness spike, influenced by the composition and structure of the particles emitted from the 3I/ATLAS jet, as noted by Professor Loeb in the statement.
This image of interstellar comet 3I/ATLAS was taken by Hubble’s WFC3 instrument on January 22, 2026, at 13:40 UTC. Image credit: NASA / ESA / Hubble / Man Tu Hui, Shanghai Observatory.
Astrophysicist Mang To Hui from the Shanghai Observatory utilized Hubble’s capabilities to observe 3I/ATLAS during conditions that may not occur again for decades.
The interstellar object images were gathered using Hubble’s Wide Field Camera 3 (WFC3) instrument, providing valuable data for ongoing research.
Professor Loeb elaborated on the findings, stating, “When the Hubble images from the January 22, 2026, alignment were processed by my collaborator Toni Scarmato, they revealed a system of four jets, including a prominent tail directed toward the Sun and Earth, along with three smaller ‘minijets.’”
“These minijets are spaced evenly apart at 120-degree angles, with one possibly hidden from view due to its unfavorable orientation relative to Earth, rendering it dark.”
NASA’s SPHEREx mission reveals that interstellar object 3I/ATLAS dramatically transformed into an active comet following its close approach to the Sun.
SPHEREx imaging of 3I/ATLAS taken from December 8th to 15th, 2025. Image credit: NASA / arXiv: 2601.06759.
SPHEREx monitored 3I/ATLAS from December 8 to 15, 2025, shortly after its perihelion, the closest approach to the Sun.
“In December 2025, SPHEREx reobserved 3I/ATLAS post-perihelion and found it to be far more active than previously observed. August 2025 SPHEREx pre-perihelion observations show significant evidence that it has completely sublimated its ice, transforming into a comet,” explained astronomer Carrie Risse from Johns Hopkins University Applied Physics Laboratory.
New SPHEREx data indicates a gas- and dust-rich coma, revealing emissions of cyanide (CN), water (H2O), organic compounds (CH), carbon dioxide (CO2), and carbon monoxide (CO).
“The emergence of cyanide and organic matter indicates their presence in the aqueous phase,” said Avi Loeb, a Harvard University professor not involved in this study.
Researchers noted a sharp increase in water activity, accompanied by a significant surge in carbon monoxide emissions.
“The H2O gas signature, previously nearly undetectable in August, is now 20 times stronger, indicating complete sublimation of water,” added the researchers.
“CO emission rates have increased by 20 times, as the CO/CO2 ratio has risen 15-fold as well.”
SPHEREx images further demonstrate that the object’s gaseous envelope has expanded significantly.
“The gas comas observed by SPHEREx are distinctly resolved, extending from 1 foot to 3 feet in radius; all but the CN and CH organic comas appear round relative to the Sun and orbital velocity,” scientists noted.
“In contrast, the dust and organic matter images in the SPHEREx continuum exhibit a pear-shaped morphology, with the ‘pear stalk’ directed toward the Sun.”
“These varying shapes suggest that CN and CH are sourced from dust, while H2O, CO2, and CO gases are distributed symmetrically around the atomic nucleus.”
“No visible jets or anti-solar tail structures were detected.”
SPHEREx’s observations indicate fundamental changes in the physical state of 3I/ATLAS.
“December 2025’s observations align with a comet that is fully active and sublimating water ice,” the authors concluded.
The composition now resembles that of typical Solar System comets, with ice content comparable to most comets.
Researchers attribute these changes to the object’s trajectory through the inner solar system.
“By December, 3I/ATLAS had spent 3.5 months within the solar system’s ice line, causing all comet components and volatile CO2 ice to become active,” they stated.
“Consequently, the bulk material of the cometary matrix evaporated, releasing its contents.”
“Further observations are anticipated before 3I/ATLAS passes through SPHEREx’s investigation pattern again in April 2026,” they concluded.
For more information, refer to their paper, submitted for publication in AAS Research Notes.
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CM Lisse et al. 2026. SPHEREx reobservations of interstellar object 3I/ATLAS in December 2025: increased post-perihelion activity, detection of coma dust, and new gaseous emissions. RNAAS submitted for publication. arXiv: 2601.06759
A global team of astronomers from Chile, Europe, the USA, Canada, and New Zealand has achieved an unprecedented level of detail in spectroscopic observations of an interstellar comet as it moves through our solar system. Utilizing spectroscopic data from two instruments on the ESO’s Very Large Telescope (VLT), researchers detected emissions of nickel atoms and cyan gas from the interstellar comet 3I/ATLAS, marking it as the third confirmed interstellar object recorded.
This image of interstellar comet 3I/ATLAS was taken with Hubble’s Wide Field Camera 3 (WFC3) on December 27, 2025. Image credit: NASA/ESA/CSA/Hubble.
The interstellar traveler, 3I/ATLAS, was first discovered on July 1, 2025, using the NASA-funded ATLAS (Asteroid Terrestrial Impact Last Alert System) telescope.
Also referred to as C/2025 N1 (ATLAS) and A11pl3Z, this celestial object approached from the constellation Sagittarius.
At its discovery, the comet was located 4.51 astronomical units (AU) from the Sun, with an eccentricity of 6.13.
“Understanding the volatile components of interstellar objects that pass through our solar system grants us unique insights into the chemical and physical processes occurring in distant stellar systems,” noted Dr. Rohan Rahatgaonkar of the Catholic University of Chile.
“Interstellar objects maintain remnants of the chemical and physical processes active in their protoplanetary disks during formation and may be altered by interstellar medium exposure.”
“When subjected to solar radiation, these cometary interstellar objects emit solids and gases due to their activity.”
During July and August, astronomers carried out high-resolution spectroscopic analyses as 3I/ATLAS approached between 4.4 to 2.85 AU from the Sun.
To acquire the comet’s spectrum, they employed the VLT’s X-Shooter and the Ultraviolet and Visible Echelle Spectrometer (UVES).
Observations revealed that the comet’s coma, the cloud of dust and gas enveloping its nucleus, is primarily made up of dust, with a consistent reddish optical continuum indicating organic-rich materials.
This reddish coloration resembles that of comets within our solar system and primitive Kuiper belt objects, suggesting shared physical processes across the planetary system.
3I/ATLAS spectrum showing Ni I emission over observations from VLT/X-Shooter and VLT/UVES. Image credit: Rahatgaonkar et al., doi: 10.3847/2041-8213/ae1cbc.
As 3I/ATLAS continued its journey towards the Sun, researchers identified emissions of various cyanide (CN) compounds and neutral nickel (Ni).
Interestingly, iron (Fe) was not detected, implying that nickel is efficiently released by comatose dust particles under solar radiation influence.
The rate of production for these emissions increases significantly as the comet nears the Sun, establishing a strong power-law relationship with its geocentric distance.
These observations indicate that the release of these atoms may stem from low-energy mechanisms, like photon-stimulated desorption or the breakdown of complex organics, rather than the direct sublimation of ice. This distinguishes this interstellar comet from many others within the solar system.
This spectral data not only acts as a snapshot of a transient visitor, but interstellar comets like 3I/ATLAS offer pristine samples from materials formed around other stars. Their limited processing from solar proximity preserves valuable clues about distant protoplanetary disks—the swirling clouds of gas and dust which eventually form planets.
Past interstellar discoveries, such as ‘Oumuamua in 2017 and 2I/Borisov in 2019, have exhibited surprising contrasts. ‘Oumuamua appeared inert, while 2I/Borisov showcased an abundance of carbon monoxide and complex ice.
The new insights from 3I/ATLAS contribute another intriguing layer to this expanding cosmic narrative. Its dusty constitution reveals molecular traits that challenge our understanding of typical comet behavior and introduce novel physics.
3I/ATLAS spectrum from the monitoring campaign spanning July 4 to August 21, 2025. Image credit: Rahatgaonkar et al., doi: 10.3847/2041-8213/ae1cbc.
“If 3I/ATLAS maintains the absence of iron while exhibiting nickel emissions during perihelion, it will set a precedent for observing interstellar comet metal emissions decoupled from traditional refractory trends,” the researchers stated.
“This observation suggests a distinct low-temperature organometallic pathway for nickel in exocomets and may provide fresh perspectives on how disk chemistry, metallicity, and irradiation history affect planetesimal microphysics.”
The parent star of 3I/ATLAS is presumed to be less metallic than other interstellar progenitor stars, yet more metallic than the Sun, indicating no inherent conflict between its estimated age and the presence of iron-peak elements like nickel.
“Regardless of which interpretation is accurate, 3I/ATLAS promises a critical experiment linking metal emissions with volatile activation and particle physics in interstellar bodies.”
“The findings discussed will elevate nickel from being a mere curiosity into a crucial marker for determining both parent chemistry and galactic origins, and set new standards for rapid-response spectroscopy of interstellar objects at the Rubin Observatory and ESO’s Very Large Telescope.”
For further details, see the published findings on December 10, 2025, in the Astrophysics Journal Letter.
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Rohan Rahat Gaonkar et al. 2025. Observations of interstellar comet 3I/ATLAS using a very large telescope: From quiescence to luminescence—Dramatic increases in Ni i emissions and initial CN outgassing at extensive heliocentric distances. APJL 995, L34; doi: 10.3847/2041-8213/ae1cbc
Scientists utilized the WISPR (Wide Field Imager for Solar Exploration) instrument on NASA’s Parker Solar Probe to capture stunning images of the interstellar comet 3I/ATLAS between October 18 and November 5, 2025.
WISPR captures the interstellar comet 3I/ATLAS. Image credit: NRL / NASA / JHUAPL / Guillermo Stenborg, JHUAPL.
Discovered on July 1, 2025, by the NASA-funded ATLAS survey telescope in Rio Hurtado, Chile, 3I/ATLAS, also known as C/2025 N1 (ATLAS) and A11pl3Z, originated from the constellation Sagittarius.
This remarkable interstellar comet approached Mars on October 3 at a distance of just 0.194 AU and reached its perihelion, the closest point to the Sun, on October 30.
On December 19, 3I/ATLAS made its nearest pass to Earth, coming within 270 million kilometers (168 million miles) of our planet.
The spectacular images of 3I/ATLAS were obtained by the WISPR instrument aboard NASA’s Parker Solar Probe during a critical observation window from October 18 to November 5.
“The Parker Solar Probe captured around 10 images of the comet daily,” stated WISPR team members.
“During this observation period, the spacecraft accelerated away from the Sun following its 25th solar flyby on September 15.”
“These initial images are currently undergoing calibration and processing, revealing the comet’s movement behind the Sun from Parker’s vantage point.”
“At that time, the comet was located about 209 million kilometers (130 million miles) from the Sun, just beyond Mars’ orbit.”
“These images offer a rare opportunity to study the comet when it was too close to the Sun for ground-based observations.”
The WISPR team is diligently working to finalize the data by eliminating stray light and adjusting for varying exposure times between images, enhancing the comet’s visibility.
“The final images will significantly advance our understanding of this intriguing interstellar visitor,” researchers concluded.
Utilizing the Ultraviolet Spectroscopy (UVS) instrument onboard NASA’s Europa Clipper spacecraft, scientists have made significant observations of 3I/ATLAS. This interstellar object is the third and only confirmed of its kind to have been detected entering our solar system from beyond it. While many telescopes on Earth and Mars struggled to track such interstellar visitors due to their proximity to the Sun, Europa Clipper was able to gather data from a distinct position as it advanced towards Jupiter.
This composite image of interstellar comet 3I/ATLAS was captured on November 6, 2025, by the UVS instrument aboard NASA’s Europa Clipper spacecraft from a distance of around 164 million kilometers (103 million miles). Image Credit: NASA/JPL-Caltech/SwRI.
Scheduled to launch in 2024 and reach the Jupiter system by 2030, Europa Clipper will orbit Jupiter and conduct 49 flybys of its icy moon, Europa.
The UVS instrument specializes in collecting ultraviolet light to analyze the composition of Europa’s atmospheric gases and the materials on its icy surface.
Dr. Curt Retherford, principal investigator for Europa-UVS and a research scientist at the Southwest Research Institute, remarked, “This unexpected opportunity to observe another target on its journey to Jupiter has us very excited.”
“Our observations offer a distinctive and detailed view of the comet.”
Discovered on July 1, 2025, by the NASA-funded ATLAS survey telescope in Rio Hurtado, Chile, 3I/ATLAS was traveling at a heliocentric distance of 4.51 astronomical units (AU) with an eccentricity of 6.13 at that time.
Within a week of its discovery, the Jet Propulsion Laboratory’s analysts had determined its trajectory through the solar system.
The Europa Clipper team quickly identified that their spacecraft could view 3I/ATLAS in November 2025, especially after Earth-based observations were largely obstructed by the Sun’s position and Mars observations became optimal.
During this period, the spacecraft provided crucial data between the Mars observations in September and upcoming Earth-based exams.
With the comet’s trajectory aligning between Europa Clipper and the Sun, the UVS team was able to observe it from a distinctive angle.
Comets feature a dust tail that trails behind and a plasma tail that extends away from the Sun.
The Europa-UVS’s unique sunward perspective enabled a rare downstream view of the comet’s two tails, primarily observing from behind the tail and toward the comet’s core and coma.
“We anticipate that this new perspective, together with data from Earth-based assets and other spacecraft, will enhance our understanding of the tail’s shape,” stated Dr. Thomas Greathouse, co-principal investigator for the Europa-UVS study.
The UVS instrument identified signatures associated with oxygen, hydrogen, and dust, reinforcing evidence of significant outgassing activity from 3I/ATLAS shortly after its closest approach to the Sun.
“Europa-UVS excels at measuring fundamental transitions of atoms and molecules,” remarked Dr. Retherford.
“We can observe gas being expelled from the comet, along with water molecules splitting into hydrogen and oxygen atoms.”
This capability allows Europa Clipper to closely analyze and measure these atomic species, offering deeper insights into the comet’s processes and composition.
“By understanding the chemical makeup of comets and how readily these gases are ejected, we can better comprehend their origins and evolution as they traverse from distant parts of the galaxy to our solar system,” explained Dr. Tracy Becker, co-principal investigator for Europa and UVS, also at the Southwest Research Institute.
“What chemical processes occur? How can we grasp the origins of comets within our solar system?”
“Are these processes akin to our theories about the formation of the solar system? That’s a key question.”
On November 26, 2025, astronomers utilized the Gemini Multi-Object Spectrograph (GMOS) on the Gemini North Telescope located on Mauna Kea, Hawaii, to capture images of the interstellar comet 3I/ATLAS. Recent observations demonstrate how this comet has evolved since its closest approach to the Sun.
This image, taken with GMOS on the Gemini North Telescope, depicts 3I/ATLAS traveling among stars and galaxies. Operating as part of the International Gemini Observatory, it is funded in part by NSF and managed by NSF’s NOIRLab. Image credit: International Gemini Observatory / NOIRLab / NSF / AURA / B. Bolin / J. Miller & M. Rodriguez, International Gemini Observatory & NSF’s NOIRLab / TA Rector, University of Alaska Anchorage & NSF’s NOIRLab / M. Zamani, NSF’s NOIRLab.
3I/ATLAS reached its closest approach to the Sun, termed perihelion, on October 30, 2025.
Having emerged from behind the Sun, this interstellar body was observed near Zania, a triple star system situated in the Virgo constellation.
On November 26, 2025, researcher Bryce Bolin from Eureka Scientific, along with colleagues, obtained new images of the comet as part of a public outreach initiative by NSF NOIRLab in partnership with Shadow the Scientist.
“Providing the public with a viewing experience under optimal conditions allows for a genuine front-row glimpse of interstellar visitors,” Dr. Bolin stated.
“Offering the public insight into our work as astronomers and our methodologies also serves to demystify science and the data collection process, enhancing transparency in the study of this captivating astronomical entity.”
The 3I/ATLAS image, captured using GMOS, highlights the comet’s coma—a cloud of gas and dust that forms around its icy center when approaching the Sun. Image credit: International Gemini Observatory / NOIRLab / NSF / AURA / B. Bolin / J. Miller & M. Rodriguez, International Gemini Observatory & NSF’s NOIRLab / TA Rector, University of Alaska Anchorage & NSF’s NOIRLab / M. Zamani, NSF’s NOIRLab.
The recent GMOS image comprises exposures taken through four different filters: blue, green, orange, and red.
“During the exposure, the comet remains stationary in the center of the telescope’s field of view,” the astronomers explained.
“However, the background stars shift in relation to the comet, creating colorful streaks in the final image.”
“Initial images of the comet from the Shadow the Scientist session at Gemini South, Chile, exhibited a red hue.”
“In contrast, the new images released today display a subtle greenish glow.”
“This phenomenon results from light emitted by gases in the comet’s coma containing diatomic carbon, a reactive molecule made of two carbon atoms that emits light at green wavelengths. This gas evaporates as the comet heats up.”
“What remains uncertain is how comets behave as they move away from the Sun and cool down.”
“Many comets respond slowly to the Sun’s heat, as it takes time for the warmth to penetrate the comet’s interior.”
“Such delays could accelerate the evaporation of new compounds or potentially lead to the comet’s disintegration.”
Astronomers utilizing ESA’s XMM-Newton Observatory have captured X-ray images of 3I/ATLAS, the third confirmed interstellar object to traverse our solar system, following 1I/Oumuamua and 2I/Borisov.
This XMM-Newton image displays an X-ray visualization of the interstellar comet 3I/ATLAS. The center features a bright red dot against a dark backdrop, resembling a burning lighthouse. Surrounding this core is a soft gradient of purple and blue, forming a slightly rotated rectangular frame divided by a thin horizontal line, indicating the detector gap. Red represents low-energy X-rays, while blue signifies regions with minimal X-rays. Image credit: ESA / XMM-Newton / C. Lisse / S. Cabot / XMM ISO Team.
On December 3, 2025, XMM-Newton tracked the interstellar comet 3I/ATLAS for approximately 20 hours.
During this observation, the interstellar object was about 282-285 million kilometers away from the spacecraft.
XMM-Newton utilized the European Photon Imaging Camera (EPIC)-PN, its most sensitive X-ray camera, to observe the comet.
“This XMM-Newton image highlights the comet radiating in low-energy X-rays. The blue regions indicate voids with nearly no X-rays, while the red areas showcase the comet’s X-ray emissions,” stated members of the XMM-Newton team.
Astronomers anticipated this glow, as gas molecules emitted from comets generate X-rays upon colliding with the solar wind.
“These X-rays can originate from the interaction of the solar wind with gases such as water vapor, carbon dioxide, and carbon monoxide, and have previously been detected by telescopes like NASA/ESA/CSA’s James Webb Space Telescope and NASA’s SPHEREx,” added the researchers.
“However, these telescopes possess distinct sensitivities to gases like hydrogen and nitrogen.”
“They are almost undetectable by optical and ultraviolet instruments, such as the NASA/ESA Hubble Space Telescope and ESA’s JUICE camera.”
“This makes X-ray observation an exceptional resource,” they emphasized.
“Researchers will be able to identify and examine gases that are difficult to detect with alternative instruments.”
“Multiple scientific groups suggest that the first observed interstellar object, 1I/’Oumuamua, may have been composed of unusual ices like nitrogen and hydrogen.”
“Although 1I/Oumuamua is currently too distant to study, 3I/ATLAS provides fresh opportunities to investigate interstellar bodies. X-ray observations will supplement other data and assist scientists in understanding the composition of these objects.”
The Hubble team has unveiled breathtaking new images of interstellar comet 3I/ATLAS captured by the NASA/ESA Hubble Space Telescope. This marks only the third instance of such a comet being observed.
This image of interstellar comet 3I/ATLAS was captured by Hubble on November 30, 2025. At that time, the comet was around 286 million kilometers (178 million miles) from Earth. Image credits: NASA / ESA / STScI / D. Jewitt, UCLA / M.-T. Hui, Shanghai Observatory / J. DePasquale, STScI.
Discovered on July 1, 2025, by the NASA-funded ATLAS (Asteroid Terrestrial Impact Last Alert System) survey telescope in Rio Hurtado, Chile, 3I/ATLAS is a remarkable interstellar comet.
At the time of its discovery, the comet had a heliocentric distance of 4.51 astronomical units (AU) and an eccentricity of 6.13.
This object, also referred to as C/2025 N1 (ATLAS) and A11pl3Z, approaches from the direction of the constellation Sagittarius, traveling at an impressive radial velocity of about 58 km (36 miles) per second.
3I/ATLAS passed near Mars at a distance of 0.194 AU on October 3 and reached its closest encounter with the Sun, known as perihelion, on October 30.
On March 16, 2026, this interstellar visitor will approach Jupiter at a distance of 0.357 astronomical units.
“Hubble tracked a comet across the sky,” they stated.
“As a result, the background stars appear as streaks of light.”
“Hubble had previously observed 3I/ATLAS in July, shortly after its discovery, and several NASA missions have also studied the comet since then.”
“Observations are expected to persist for several more months as 3I/ATLAS journeys out of the solar system.”
“This image displays a teardrop-shaped glowing halo extending toward the sun,” stated Harvard University Professor Avi Loeb about the new Hubble images.
“This extension of the tail toward the sun was also noticeable in the pre-perihelion Hubble images taken on July 21, where 3I/ATLAS was approaching the Sun from a distance 56% greater than that of Earth.”
“The new radius of the glow is estimated to be around 40,000 km (24,855 miles), with its retro tail extension reaching approximately 60,000 km (37,282 miles).”
“In recent papers, I suggested that the coma teardrops in the 3I/ATLAS post-perihelion images are linked to numerous macroscopic non-volatile objects that have separated from the Sun due to measurements of non-gravitational accelerations moving away from the Sun,” he elaborated.
“I predicted that if the object overlapped with 3I/ATLAS at perihelion, by November 30th, the swarm would be about 60,000 km closer to the Sun than 3I/ATLAS.”
“This separation aligns perfectly with the teardrop-shaped anti-caudal extension visible in the new Hubble image.”
Comet 3I/ATLAS is the third known visitor from beyond our solar system
International Gemini Observatory/NOIRLab/NSF/AURA/Shadow the Scientist; J. Miller & M. Rodriguez (International Gemini Observatory/NSF NOIRLab), T.A. Rector (University of Alaska Anchorage/NSF NOIRLab), M. Zamani (NSF NOIRLab)
The interstellar comet 3I/ATLAS releases carbon-rich compounds at a higher rate than most comets in the solar system, including methanol. This compound plays a crucial role in prebiotic chemistry and is not commonly found in other interstellar objects.
Having made only three known visits to our solar system, 3I/ATLAS stands apart from comets found in our galactic neighborhood. While approaching the Sun, it developed a crust of water vapor and gas, containing significantly more carbon dioxide than typically found in Solar System comets. Additionally, the comet’s light appeared unusually red, hinting at atypical surface chemistry, and it began emitting gas well before reaching the Sun. This could indicate that it has not approached another star in hundreds of millions of years, or possibly since leaving its home system.
Recently, Martin Cordiner and a team using the Atacama Large Millimeter/Submillimeter Array (ALMA) in Chile discovered that 3I/ATLAS generates significant amounts of hydrogen cyanide gas, as well as even larger quantities of gaseous methanol. “Hydrogen cyanide and methanol are usually found in trace amounts and aren’t dominant components in our comets,” explained Cordiner. “However, they appear to be notably abundant in this alien comet.”
Cordiner’s research team observed that the hydrogen cyanide comes from near the comet’s core, producing around a quarter to half a kilogram per second. Methanol was also found in the core, indicating large quantities are produced even within the comet’s coma, which is the extensive trail of dust and gas extending miles away from the comet itself.
Methanol is emitted at approximately 40 kilograms per second, significantly more than hydrogen cyanide, which represents about 8 percent of the total vapor released (compared to roughly 2 percent from typical solar system comets). The different locations of these two molecules suggest that the comet’s core may not be uniform, which could provide insights into how comets are formed, according to Cordiner.
Cordiner noted that, while methanol is a relatively straightforward carbon-based compound, it plays an essential role in forming more complex molecules critical for life. Its production appears to be high when chemical reactions producing these larger molecules occur. “Chemically, it seems unlikely that we can progress toward highly complex substances without generating methanol,” Cordiner said.
Josep Trigo-Rodriguez and colleagues from Spain’s Institute of Space Sciences suggested that comets with substantial iron and metals are likely to produce considerable methanol as well. The presence of liquid water heated by the Sun could permeate the comet’s core and engage in chemical reactions with its iron, resulting in methanol production. Thus, discovering methanol in the coma might indicate a metal-rich composition of the comet, he adds.
In November 2025, ESA’s Jupiter Ice Satellite Probe (Juice) utilized five scientific instruments to study 3I/ATLAS, marking the second interstellar comet ever identified in our neighboring universe. The spacecraft also captured fresh images of this interstellar traveler using its navigation camera (NavCam).
This image from ESA’s Juice spacecraft captures the interstellar comet 3I/ATLAS. Image credit: ESA / Juice / NavCam / CC BY-SA 3.0 IGO.
“Though the data from the scientific instruments won’t reach Earth until February 2026, our team was eager to see what we could find,” stated members of the Juice team.
“We opted to download just a quarter of a single NavCam image to test the waters.”
“To our astonishment, we clearly observed a comet, notably surrounded by signs of activity.”
“You can distinctly see the glowing gas surrounding the comet, referred to as the coma, along with indications of its two tails.”
“The comet’s ‘plasma tail,’ composed of electrically charged gas, stretches toward the top of the image.”
“A fainter ‘dust tail,’ made of tiny solid particles, can also be seen extending to the bottom left.”
Annotated version of the Juice image depicting interstellar comet 3I/ATLAS. Image credit: ESA / Juice / NavCam / CC BY-SA 3.0 IGO.
The image of 3I/ATLAS was captured on November 2, during the initial observation window of Comet Juice.
This observation took place on November 4, just two days before Juice’s closest approach to the comet, approximately 66 million kilometers (41 million miles) away.
“On February 18 and 20, 2026, we will receive data from the five scientific instruments (JANUS, MAJIS, UVS, SWI, PEP) activated during the observation,” the researchers mentioned.
“This delay results from Juice currently using its main high-gain antenna as a heat shield against the sun, while a smaller medium-gain antenna transmits data to Earth at a slower rate.”
Even though Juice was situated farther from 3I/ATLAS than ESA’s Mars rover—which returned in October—it observed 3I/ATLAS shortly after the comet’s closest proximity to the Sun, suggesting a more active state.
“We anticipate clearer indications of this activity with data from our scientific instruments,” the scientists elaborated.
“This will encompass not only visuals from JANUS (Juice’s high-resolution optical camera), but also spectrometry data from MAJIS and UVS, compositional insights from SWI, and particle data from PEP.”
NASA’s Psyche spacecraft has obtained fresh images of 3I/ATLAS, marking it as the third astronomical object and the second comet observed from outside our solar system.
Psyche secured four observations of 3I/ATLAS over an 8-hour period on September 8 and 9, 2025. Image credit: NASA/JPL-Caltech/ASU.
3I/ATLAS was found on July 1, 2025, by the ATLAS survey telescope located in Rio Hurtado, Chile.
The orbits of interstellar comets represent the most dynamically extreme pathways of any astronomical object recorded within our solar system.
Known also as C/2025 N1 (ATLAS) and A11pl3Z, 3I/ATLAS reached its closest point to the Sun on October 30, 2025.
The latest images of the comet were captured during an eight-hour window on September 8 and 9, 2025, when 3I/ATLAS was roughly 53 million kilometers (33 million miles) away from NASA’s Psyche spacecraft.
“The observations collected by the mission’s multispectral imager will assist in refining the trajectory of 3I/ATLAS,” stated members of the Psyche team.
“Psyche’s multispectral imager consists of a pair of identical cameras fitted with filters and telephoto lenses to photograph the surface of the metal-rich asteroid Psyche across various wavelengths of light.”
“During these observations, Comet 3I/ATLAS was moving away from the spacecraft, but the imager’s sensitivity to the comet’s reflected sunlight allowed for accurate tracking of the object.”
The recent observations further illuminate the faint coma—a cloud of gas and dust—surrounding 3I/ATLAS’ core, which is a frozen mixture of ice and rock.
“Psyche will collaborate with numerous other NASA missions to track the positions of comets over time, aiding astronomers in comprehending the movement of such objects within our solar system,” researchers stated.
“Though comets do not pose a direct threat to Earth, NASA’s space missions contribute to ongoing efforts to discover, monitor, and better understand objects in our Solar System.”
NASA’s STEREO (Solar-Earth Relations Observatory), the NASA/ESA SOHO (Solar-Heliospheric Observatory), and NASA’s PUNCH (Corona-Heliosphere Integrating Polarimeter) missions had the extraordinary capability to observe sky regions near the Sun, enabling them to monitor 3I/ATLAS as it traversed behind the Sun from Earth’s perspective.
3I/ATLAS moves at an incredible speed of 209,000 km (130,000 miles) per hour, visualized through a series of colorized stacked images captured from September 11 to 25, 2025, using the Heliocentric Imager-1 instrument aboard NASA’s STEREO-A spacecraft. Image credit: NASA / Lowell Observatory / Qicheng Zhang.
STEREO monitored the interstellar comet 3I/ATLAS between September 11 and October 2, 2025.
The mission aims to examine solar activity and its effects on the entire solar system and is part of a collection of NASA spacecraft studying comets, offering insights on their size, physical characteristics, and chemical makeup.
Initially, it was believed that comet 3I/ATLAS would be too dim for STEREO’s instruments, but advanced image processing using the visible-light telescope Heliospheric Imager-1 and the stacking of images revealed 3I/ATLAS effectively.
By overlaying multiple exposures, distinct images were produced, showing the comet slightly brighter at the center.
This image of 3I/ATLAS combines observations from the NASA/ESA SOHO mission between October 15 and 26, 2025. Image credit: NASA / ESA / Lowell Observatory / Qicheng Zhang.
The SOHO spacecraft managed to catch a glimpse of 3I/ATLAS from October 15 to 26, 2025.
During this time frame, the LASCO instrument suite onboard SOHO identified comets crossing its observation area from around 358 million km (222 million miles) away, which is more than twice Earth’s distance from the Sun.
SOHO orbits at Sun-Earth Lagrange Point 1, a gravitational equilibrium point approximately 1.6 million km (1 million miles) closer to the Sun along the Sun-Earth axis.
Members of the SOHO team also utilized stacking techniques to create images of 3I/ATLAS.
In this image, 3I/ATLAS is clearly visible as a bright object in the center, created by consolidating observations from NASA’s PUNCH mission conducted from September 20 to October 3, 2025. Image credit: NASA/Southwest Research Institute.
The PUNCH mission observed 3I/ATLAS from September 20 to October 3, 2025.
These observations indicated that the comet’s tail extended slightly to the lower right.
During this period, the comet was so dim that the PUNCH team was uncertain if the spacecraft would be able to detect it well, given its primary focus on studying the Sun’s atmosphere and solar wind rather than comets.
However, by collecting multiple observations, 3I/ATLAS and its tail became distinctly visible.
“We’re truly pushing the limits of this system,” stated Dr. Kevin Walsh, a planetary scientist at the Southwest Research Institute who led the PUNCH observations of comets.
Recent ultraviolet (UV) images from the imaging ultraviolet spectrometer (IUVS) on NASA’s MAVEN (Mars Atmosphere and Volatile Evolution) orbiter have provided unique insights into the interstellar comet 3I/ATLAS, offering details about its chemical composition and the amount of water vapor released as it warms under the Sun. These findings will aid scientists in understanding the past, present, and future of 3I/ATLAS.
This ultraviolet image displays the coma of 3I/ATLAS as observed on October 9, 2025, by NASA’s MAVEN spacecraft utilizing its IUVS camera. The brightest pixel in the center marks the comet’s location, while the surrounding bright pixels show the presence of hydrogen atoms emanating from the comet. Image credit: NASA/Goddard/LASP/CU Boulder.
MAVEN captured images of 3I/ATLAS over a span of 10 days starting September 27, 2025, using IUVS cameras in two distinctive methods.
Initially, IUVS generated multiple images of the comet across several wavelengths, akin to using various filters on a single camera.
Subsequently, high-resolution UV images were obtained to identify the hydrogen emitted by 3I/ATLAS.
Analyzing these images together allows researchers to pinpoint various molecules and gain a deeper understanding of the comet’s makeup.
“The images gathered by MAVEN are truly astounding,” remarked Dr. Shannon Currie, MAVEN’s principal investigator.
“The detections we observe are significant, and we have merely begun our analysis journey.”
This annotated composite image highlights hydrogen atoms from three origins, including 3I/ATLAS (left), captured by NASA’s MAVEN orbiter on September 28, 2025, using an IUVS camera. The bright stripe on the right corresponds to hydrogen released from Mars, while the dark stripe in the center represents interplanetary hydrogen present in the solar system. Image credit: NASA/Goddard/LASP/CU Boulder.
The IUVS data also provides an estimated upper limit on the ratio of deuterium to normal hydrogen in comets, which is crucial for tracking their origin and evolution.
During the comet’s closest approach to Mars, Curry and his team utilized IUVS’s more sensitive channel to map various atoms and molecules, such as hydrogen and hydroxyls, within the comet’s coma.
Further examination of the comet’s chemical makeup could shed light on its origins and evolutionary journey.
“I experienced a rush of adrenaline when I saw what we had documented,” stated Dr. Justin Dahan, co-principal investigator of MAVEN and a member of the Atmospheric and Space Physics Laboratory at the University of Colorado Boulder.
“Every observation we make about this comet will enhance our understanding of interstellar objects.”
This image of 3I/ATLAS was captured by the HiRISE camera aboard NASA’s Mars Reconnaissance Orbiter on October 2, 2025. Credit: NASA / JPL-Caltech / University of Arizona.
On October 2, 2025, the Mars Reconnaissance Orbiter (MRO) observed 3I/ATLAS from approximately 30 million km (19 million miles) away.
The MRO team utilized the High-Resolution Imaging Science Experiment (HiRISE), which typically focuses on the Martian surface.
By maneuvering, the spacecraft can direct its camera toward other celestial objects. This method was previously employed in 2014 when HiRISE collaborated with MAVEN to examine the comet Siding Spring.
“Observations of interstellar objects are still infrequent, so each time we learn something new,” noted Dr. Shane Byrne, HiRISE principal investigator and researcher at the University of Arizona.
“We were fortunate that 3I/ATLAS came close to Mars.”
Captured at a resolution of about 30 km (19 miles) per pixel, 3I/ATLAS appears as a pixelated white sphere in the HiRISE images.
“This sphere is a cloud of dust and ice, referred to as a coma, that the comet emits as it travels past Mars,” the researchers added.
Further analysis of HiRISE images could assist scientists in establishing an upper limit on the size of a comet’s core, composed of ice and dust.
The images might also uncover properties of particles known as comas within the comet’s atmosphere.
Ongoing scrutiny of the images may reveal nuclear fragments and gas jets expelled as comets disintegrate over time.
“One of MRO’s greatest contributions to NASA’s Mars research is its ability to observe surface phenomena that only HiRISE can detect,” explained Dr. Leslie Tampali, MRO’s project scientist and a research scientist at NASA’s Jet Propulsion Laboratory.
“This opportunity allows us to study passing space objects.”
“Thanks to NASA’s versatile fleet of spacecraft throughout our solar system, we can continue to observe this dynamic entity from unique perspectives,” stated Georgia Tech researcher Professor James Ray, a HiRISE co-investigator.
“All three prior interstellar objects exhibit significant differences from one another and from typical Solar System comets, making every new observation incredibly valuable.”
“Being able to observe a visitor from another star system is extraordinary in itself,” remarked Dr. Tomás Díaz de la Rubia, senior vice president for research and partnerships at the University of Arizona.
“Doing so from a University of Arizona-led instrument orbiting Mars adds to its remarkable nature.”
“This moment highlights the ingenuity of our scientists and the lasting impact of this university’s leadership in space exploration.”
“HiRISE exemplifies how discovery tools can benefit both science and the public interest.”
NASA unveiled new images of an interstellar comet on Wednesday, marking it as the third confirmed visitor from elsewhere in the galaxy. The visuals depict the comet as a luminous point encircled by a halo of gas and dust.
In the eagerly awaited photograph, the comet, designated 3I/ATLAS, mainly appears as an illuminated spot, though its tail can be seen as a faint elongated streak in some frames.
Interstellar comet 3I/ATLAS (highlighted in the center) as captured by NASA’s Lucy spacecraft. This image was formed by combining multiple photos taken on September 16, as the comet approached Mars. NASA / Goddard / SwRI / JHU-APL
First identified in July, comet 3I/ATLAS has generated significant excitement among scientists and astronomy enthusiasts. The fascination arises from the unique chance to observe interstellar objects at such proximity.
The latest images were captured by an array of NASA spacecraft while the enigmatic comet circled through the inner solar system from late September to mid-October. The release was delayed due to a government shutdown that interrupted operations at NASA and other federal institutions.
The NASA missions responsible for these new images include the PUNCH satellite, which observes the Sun, the Solar Heliosphere Observatory, the MAVEN mission studying Mars’ atmosphere, and the Perseverance rover, currently on Mars’ surface.
Traveling at 130,000 miles per hour, the comet 3I/ATLAS was depicted in a series of colorized stacked visuals from September 11 to 25 using the STEREO-A (Solar Terrestrial Relations Observatory) visible-light camera. NASA / Lowell Observatory / Zhang Qicheng
Prior to 3I/ATLAS, the only confirmed interstellar objects to have entered our solar system were the cigar-shaped ‘Oumuamua in 2017 and comet 2I/Borisov in 2019.
The arrival of 3I/ATLAS in our cosmic vicinity has sparked wild speculations about the possibility of it being extraterrestrial technology or an alien spacecraft, although no scientific backing supports these ideas. NASA officials stated in a press conference on Wednesday that all current observations align with known comet characteristics.
“We certainly haven’t detected any technosignatures or anything that would suggest it is anything but a comet,” remarked Nicki Fox, associate administrator for NASA’s Science Mission Directorate.
Nonetheless, the comet’s interstellar roots indicate it possesses intriguing attributes that could yield new insights regarding star systems beyond our own, according to Fox.
“That difference is particularly fascinating to us,” she stated. “It may have existed before our solar system was formed. That’s pretty exciting.”
In the forthcoming weeks, scientists will have enhanced opportunities to study 3I/ATLAS and further analyze its appearance, speed, chemical makeup, and potential origins.
“This is a new scientific chance and an opportunity to delve into the composition and history of other solar systems,” expressed Tom Statler, NASA’s lead scientist for small solar system bodies. “We’re just beginning to understand these types of objects and determining the right questions to pose about them.”
Comet 3I/ATLAS was documented by the PUNCH satellite in low Earth orbit from September 28 to October 10, when it was between 231 to 235 million miles away. NASA/Southwest Research Institute
However, tracing the comet’s origin remains challenging, Statler noted.
3I/ATLAS came closest to the Sun at the end of October and is currently continuing its path through the inner solar system. It has been so near to the Sun that it has not been visible to terrestrial telescopes recently, but NASA anticipates it will become visible again post-December.
On December 19, 3I/ATLAS is expected to make a close pass by Earth. Although it poses no threat, NASA states that the comet will remain about 170 million miles away during this encounter.
Statler indicated that the James Webb Space Telescope will observe the comet in December, while ground-based telescopes like the W.M. Keck Observatory in Hawaii are also scheduled to capture images of the comet in the future.
An image depicting interstellar comet 3I/ATLAS as it approached Mars, captured by the European Space Agency’s ExoMars Trace Gas Orbiter. European Space Agency
The photos released by NASA on Wednesday join a growing collection acquired by various spacecraft across the solar system. In early October, the European Space Agency shared 3I/ATLAS images taken by the ExoMars Trace Gas Orbiter, which showed a bright point moving through the vastness of space.
This spacecraft, co-managed by the ESA and the Russian Federal Space Agency, detected a comet approaching near Mars at that time, about 18.6 million miles away according to ESA.
NASA continues to analyze additional data gathered by the fleet of spacecraft since early October.
“There’s much more to come,” Statler remarked. “Not all data has been transmitted through NASA’s Deep Space Network yet, and there are numerous observations still planned.”
Recent observations of 3I/ATLAS, the third interstellar object confirmed to traverse the solar system following 1I/Oumuamua and 2I/Borisov, reveal a sophisticated multi-jet configuration.
The image of 3I/ATLAS was captured by Lowell Observatory astronomer Qicheng Zhang on October 31, 2025. Image credit: Qicheng Zhang / Lowell Observatory.
Discovered on July 1, 2025, by the NASA-funded ATLAS (Asteroid Terrestrial Impact Last Alert System) survey telescope in Rio Hurtado, Chile, 3I/ATLAS is also referred to as C/2025 N1 (ATLAS) and A11pl3Z.
Originating from the direction of the Sagittarius constellation, this comet holds the designation of being the most dynamically extreme object recorded, characterized by its hyperbolic orbit with high eccentricity and extreme hyperbolic velocity.
3I/ATLAS came closest to the Sun, reaching perihelion, on October 30, 2025.
This interstellar visitor approached within 1.4 AU (astronomical units), or approximately 210 million km, of the Sun, which is just inside Mars’ orbit.
At perihelion, the comet traveled at a remarkable speed of about 68 km/s, and its proximity to the Sun temporarily rendered it invisible to Earth’s telescopes.
Following perihelion, it will once again be observable through telescopes until December as it gradually distances itself from both the Sun and Earth, returning to interstellar space.
The initial post-perihelion optical image of 3I/ATLAS (as shown above) was captured. This was announced on October 31 by astronomer Zhang Qicheng of Lowell Observatory using the Discovery Telescope.
This image of 3I/ATLAS was taken on November 8, 2025 by astronomers from the ICQ Comet Observation Group. Image credit: M. Jaeger / G. Lehmann / E. Prosperi.
On November 8th, three astronomers from the ICQ Comet Observation Group observed the comet situated 29 degrees from the Sun in the sky.
The images they captured depict a complex jet structure with at least seven jets, including several anti-tail planes.
“Given the multitude of jets emerging in various directions, the noted non-gravitational acceleration of 3I/ATLAS implies that more than 10 to 20 percent of its initial mass would need to be ejected near perihelion,” remarked Professor Avi Loeb of Harvard University discussing the ICQ images. He stated,
“Only a small fraction of this mass carries the necessary momentum in the favored direction.”
“Consequently, the debris cloud enveloping 3I/ATLAS likely constitutes a considerable portion of the comet’s original mass.”
This 3I/ATLAS image was taken on November 9, 2025, by astronomers from the British Astronomical Society. Image credit: Michael Buechner / Frank Niebling.
On November 9th, two astronomers from the British Astronomical Association (BAA) studied the comet using two telescopes.
Their combined image displayed a long “smoking” tail along with two anti-tail jets.
“3I/ATLAS is expected to make its closest approach to Earth on December 19, 2025, making the multijet structure an intriguing target for future observations with the Hubble and Webb telescopes,” Professor Loeb mentioned discussing the BAA images. He noted.
The minimum distance to Earth will be 269 million km, roughly 100 times the extent of the jet structure illustrated in the image.
This striking image of 3I/ATLAS was taken by the International Gemini Observatory in Chile, revealing the comet’s coma formed of gas and dust.
Image Credit: International Gemini Observatory/NOIRLab/NSF/AURA/Shadow the Scientist
3I/ATLAS, an interstellar comet traversing our solar system, presents a challenge in determining its origin due to potential alterations from cosmic rays over billions of years that could have completely transformed its characteristics.
Initially detected in July, astronomers have begun to analyze its intriguing traits, including its coma, which features carbon dioxide levels at least 16 times greater than standard comets in our solar system, marking it as one of the most CO2-rich comets ever seen.
While some researchers theorized that this might indicate an unusual star system as the comet’s birthplace (or, less plausibly, a link to extraterrestrial life), a more straightforward explanation has emerged.
Roman Maggiolo and colleagues from the Belgian Royal Institute for Astronautics and Aeronautics assert that the elevated CO2 concentrations are likely a result of significant alterations to the outer layers of 3I/ATLAS over billions of years due to cosmic rays.
“This slow process has often been neglected or underestimated, yet it profoundly impacts objects like comets and interstellar bodies,” Maggiolo states.
The team compared their findings from 3I/ATLAS to lab experiments that simulate cosmic ray bombardment of ice composed of water and carbon monoxide, akin to that found on comets. These experiments revealed that this process generates substantial CO2 and leaves behind a carbon-rich residue that aligns with observations from the comet.
“Gradually, cosmic rays create reactive radicals—molecular fragments that break down and reform, thereby altering the ice’s chemical makeup,” Maggiolo explains.
This revelation poses a setback for comprehending the origins of comets, as cosmic rays can obliterate critical evidence. Previously, astronomers thought interstellar comets like 3I/ATLAS were remarkably preserved, acting as cold fossils with vital data about other star systems; however, a more cautious approach may now be necessary concerning the insights they can provide.
Although its swift passage through the solar system limits the chances for satellites to explore and directly sample these comets, there remains a sliver of hope for clarifying the true nature of 3I/ATLAS.
Currently, the comet is nearing the Sun and isn’t visible from Earth but is anticipated to resurface in December. This close encounter might result in sufficient melting of the outer ice layer to unveil materials shielded from cosmic rays, as noted by Maggiolo. However, this is contingent upon how much ice has already vanished since its entry into the solar system and the thickness of the icy crust, details that are still unclear.
Cyriel Opitum, a professor at the University of Edinburgh in the UK, emphasizes that forthcoming observations utilizing both the James Webb Space Telescope and ground-based telescopes will be essential in uncovering primitive material beneath the comet’s surface. “We are looking forward to an exciting few months ahead,” she states.
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Interstellar comet 3I/ATLAS captured by the Gemini South Telescope in Chile
International Gemini Observatory/NOIRLab/NSF/AURA/Shadow the Scientist; J. Miller & M. Rodriguez (International Gemini Observatory/NSF NOIRLab), TA President (University of Alaska Anchorage/NSF NOIRLab), M. Zamani (NSF NOIRLab)
The interstellar object 3I/ATLAS is acting oddly once more. This foreign visitor from another star is now obscured by the sun’s shadow, leading some to speculate about its secretive nature. The only likely explanation, they whisper, is that it’s an alien spacecraft.
This notion, however, is utterly baseless. It simply doesn’t hold up that a spacecraft would choose to stay hidden for just a few days while previously visible and likely to be so again. If this were actually a stealthy spacecraft, then the aliens piloting it would either be incredibly foolish or believe us to be.
How can we assert this? As an astronomer recently explained to me, if 3I/ATLAS is indeed a spacecraft, it’s doing a remarkable job of masquerading as a comet. This is what fuels the sensational discussions surrounding 3I/ATLAS (named after the eagle’s eye). planetary defense equipment (I first noticed it in July), which was both amusingly frustrating and clearly ridiculous. The evidence overwhelmingly indicates that it is a comet.
Let’s explore why. It possesses a coma, a shell of vaporized ice. It exhibits a luminous tail. Its trajectory can best be described as that of an icy projectile entering our solar system from beyond. So, why is it “hiding” behind the sun? It just reached perihelion, the closest point to our solar star in its voyage through our cosmic neighborhood. Every celestial voyager, from comets to asteroids, experiences perihelion. 3I/ATLAS happens to be behind the Sun, yet closest to it from Earth’s viewpoint.
There are certainly some intriguing aspects of 3I/ATLAS that excite astronomers. For instance, it contains a higher concentration of carbon dioxide ice compared to water ice. Nevertheless, it remains a comet, not a space probe. Some materials are composed of – hold on, aren’t those metals? Spaceships are built from metal! So, could 3I/ATLAS actually be a spacecraft? Absolutely not; we routinely observe metals in the rocky, icy cores of comets. In truth, numerous comet types exist in our solar system, many of which are indeed peculiar.
It was also somewhat unusual that at one point 3I/ATLAS had its dusty tail oriented toward the Sun instead of the opposite direction. Some speculated it was not the tail but rather a spacecraft’s exhaust plume attempting to decelerate. However, the issue is that 3I/ATLAS’s orbit is consistent with that of an interstellar comet; it’s not as if someone applied brakes to an interstellar probe. The unique orientation of its tail resulted from the specific icy, powdery particles released from its surface. This transient object would typically be pushed away from the sun by solar radiation pressure, but some of this comet’s material was so dense that it couldn’t be redirected and consequently rolled toward the sun.
3I/ATLAS is only the third interstellar object ever documented, so investigating its small population is likely to uncover some remarkable characteristics. ‘Oumuamua, the first identified interstellar visitor, was significantly stranger. Its shape was likely cigar-like, rapidly accelerating as it left the solar system. Yet even this oddity can be perfectly rationalized: it was a flashy comet-like entity. The next two interstellar objects, 2I/Borisov and 3I/ATLAS, also showcase interesting features. But to propose they are spacecraft rather than comets is equivalent to calling ice in the freezer a pineapple. You can certainly say that, but if you aim to convince me, you must present more substantial proof.
Many among us, myself included, eagerly anticipate the day we learn we’re not alone in the universe. Thus, it’s no wonder that people jump to the unfounded conclusion that 3I/ATLAS might signal that this long-awaited day has finally come. However, in an age rife with misinformation, to suggest, against overwhelming evidence, that this comet could be alien is not just misguided; it’s profoundly irresponsible.
The findings of 1I/Oumuamua, 2I/Borisov, and 3I/ATLAS have revealed a substantial number of interstellar objects in the cosmos. Their widespread presence suggests that such objects are also found in protoplanetary disks, essential sites for planet formation. In these disks, interstellar objects could potentially bypass the 1-meter (3.3-foot) barrier in the traditional model of planet formation, initiating the creation of giant exoplanets.
This colorized image was taken by the CaSSIS instrument aboard ESA’s Trace Gas Orbiter on October 3, 2025, and displays the interstellar comet 3I/ATLAS. Image credit: ESA/TGO/CaSSIS.
Interstellar objects, including asteroids and comets, are those that have been expelled from their original star systems and are now traversing interstellar space, occasionally intersecting with other star systems.
Since 2017, astronomers have identified three interstellar objects passing through our solar system: 1I/’Oumuamua, 2I/Borisov, and the latest, 3I/ATLAS.
“Nevertheless, interstellar objects may exert a more significant influence than it appears at first glance,” states Professor Susanne Falzner, an astronomer at Jülich National Park.
“Interstellar objects could potentially incite planet formation, particularly around high-mass stars.”
Planets are formed from dusty disks that surround young stars through a process known as accretion. This theory posits that smaller particles gradually coalesce into larger objects, culminating in the formation of planet-sized bodies.
However, researchers have faced challenges in explaining how accretion can create objects larger than a meter amidst the chaotic collisions of planet-forming disks surrounding young stars. In simulations, the rocks tend to either bounce off each other or break apart upon collision, rather than adhering together.
Interstellar objects might help circumvent this issue. The researchers’ model illustrates how the dust-laden disks surrounding young stars can gravitationally capture millions of interstellar objects akin to 1I/’Oumuamua, which is estimated to be around 100 meters (328 feet) long.
“Interstellar space will supply ready-made seeds for the next phase of planet formation,” said Professor Falzner.
If interstellar objects could act as seeds for planets, it would also resolve another enigma.
Gas giant planets like Jupiter are scarce around smaller and colder stars, referred to as M dwarfs, but are more frequently found around larger stars similar to the Sun.
However, the lifespan of a planet-forming disk around a Sun-like star lasts only about 2 million years before dissipating, complicating the formation of gas giant planets in such a brief time frame.
That said, if captured interstellar objects serve as seeds for accretion, the planet-forming process could hasten, allowing giant planets to form within the lifetime of the disk.
“The more massive a star is, the more effectively it can capture interstellar objects in its disk,” Professor Falzner explained.
“As a result, planet formation seeded with interstellar objects should proceed more efficiently around these stars, offering a rapid pathway to forming giant planets.”
“And their swift formation is precisely what we’ve observed.”
During its closest encounter with Mars on October 3, 2025, comet 3I/ATLAS was situated 30 million km from the ESA’s ExoMars Trace Gas Orbiter (TGO).
The image of interstellar comet 3I/ATLAS was taken on October 3, 2025, by the CaSSIS instrument aboard the ESA’s Trace Gas Orbiter. Image credit: ESA/TGO/CaSSIS.
TGO acquired new images of 3I/ATLAS utilizing the Color and Stereo Surface Imaging System (CaSSIS).
“This observation posed significant challenges for this instrument,” noted Dr. Nick Thomas, Principal Investigator of ESA’s CaSSIS instrument.
“3I/ATLAS appears as a slightly blurred white dot that descends toward the center of the image.”
“This point represents the nucleus of the comet, which comprises an icy, rocky core surrounded by a coma.”
“Due to the distance, CaSSIS couldn’t differentiate between a nuclear and a coma state.”
“The CaSSIS camera has an angular resolution of 11.36 microradians (equivalent to 2.34 arc seconds) per pixel,” explained Professor Avi Loeb from Harvard University.
“At a minimum distance of approximately 30 million km from 3I/ATLAS, this resolution translates to 340 km.”
“This pixel size is one to two orders of magnitude larger than the anticipated core diameters of 3I/ATLAS, which range from a minimum of 5 km to a maximum of 46 km.”
“Some of the expansion can be observed in CaSSIS images,” he mentioned.
“The passage of 3I/ATLAS across the Martian sky will be viewed by the Mars rover from an angle nearly perpendicular to the 3I/ATLAS-Sun axis, allowing for a side view of the glow surrounding 3I/ATLAS.”
“The width of the luminous glow around 3I/ATLAS in the CaSSIS image is approximately twice that of a bright star appearing as a background point source in the same image.”
“This span corresponds to a scale of 680 km, which is an order of magnitude smaller than the width seen in Hubble images.”
“Thus, it’s evident that CaSSIS only captures the brightest regions surrounding the core of 3I/ATLAS and cannot detect the low surface brightness envelope visible in Hubble images.”
From November 2 to 25, 2025, ESA’s Jupiter Icy Satellites probe will observe 3I/ATLAS with a range of instruments. Image credit: ESA.
“Our Mars rovers continue to contribute significantly to Mars science, and it’s always thrilling to see them respond to unforeseen scenarios like this,” remarked Dr. Colin Wilson, ESA’s Mars Express and ExoMars project scientist.
“We eagerly await the insights the data will reveal following further analysis.”
Next month, ESA researchers are set to observe 3I/ATLAS with the Jupiter Icy Satellite Orbiter (JUICE).
While JUICE will be located further from 3I/ATLAS than last week’s Mars rover, the rover will detect the comet shortly after its closest approach to the Sun, indicating heightened activity.
“Observation data for JUICE is anticipated to be received by February 2026,” they noted.
Astronomers have detected hydroxyl (OH) gas, a chemical indicator of water, from the interstellar object 3I/ATLAS using an ultraviolet/optical telescope on NASA’s Neil Gehrels Swift Observatory.
Stacked images of the interstellar comet 3I/ATLAS obtained with NASA’s Neil Gehrels Swift Observatory: the first was captured on July 31 and August 1, 2025 (visit 1, upper half), and the second was on August 19, 2025 (visit 2, lower half). Image credit: Xing et al., others, doi: 10.3847/2041-8213/ae08ab.
The identification of the third interstellar object, 3I/ATLAS, on July 1, 2025, initiated a comprehensive characterization effort globally.
Learning from prior discoveries of interstellar objects 1I/Oumuamua and 2I/Borisov, an observation campaign was implemented to swiftly measure its initial brightness, morphology, light curve, color, and optical and near-infrared spectra.
Given the apparent brightness and early extension of the coma, there was suspicion of a gas outburst, yet none was detected.
Investigating the early activity of interstellar objects is crucial for understanding their chemical and physical evolution as they approach the Sun, as this may signify the first notable heating during their extensive dynamic lifetimes.
“The discovery of water marks a significant step in our grasp of how interstellar comets evolve,” stated Dennis Bordewitz, an astronomer from Auburn University.
“For solar system comets, water serves as a baseline for scientists to gauge their total activity and track how sunlight stimulates the release of other gases.”
“This is the chemical standard against which all assessments of volatile ice in cometary cores are made.”
“Detecting the same signal in an interstellar object means we can for the first time position 3I/ATLAS on the same scale employed to study comets indigenous to our Solar System. This is a progress toward juxtaposing the chemistry of planetary systems throughout our Milky Way galaxy.”
“What’s fascinating about 3I/ATLAS is the location of this water activity.”
Swift noticed the hydroxyl groups when the comet was nearly three times further from the Sun than Earth (well beyond the area where water ice on the surface could easily sublimate), recording a water loss rate of approximately 40 kg per second. At such distances, most solar system comets remain inactive.
The robust ultraviolet signal from 3I/ATLAS implies there might be additional mechanisms at play. Possibly, sunlight is warming small ice particles expelled from the core, causing them to vaporize and contribute to the surrounding gas cloud.
Such extensive water sources have only been detected on a limited number of far-off comets, suggesting intricate layered ice that holds clues regarding their formation.
Every interstellar comet discovered to date has unveiled a distinct aspect of planetary chemistry beyond our Sun.
Collectively, these observations illustrate that the composition of comets and the volatile ice that constitutes them can vary considerably from one system to another.
These variations imply the diversity of planet-forming environments and how factors like temperature, radiation, and composition ultimately influence planetary formation and, in some instances, the materials that lead to life.
Capturing the ultraviolet signals from 3I/ATLAS was a technological achievement in itself.
Swift employs a compact 30 cm telescope, yet from its orbit above Earth’s atmosphere, it can detect wavelengths of ultraviolet light that are largely absorbed by the atmosphere.
Free from sky glare or air interference, Swift’s ultraviolet/optical telescope achieves the sensitivity comparable to that of ground-based telescopes with 4-meter apertures for these wavelengths.
Its rapid targeting abilities allowed astronomers to analyze comets just weeks after their discovery, well before they become too faint or too close to the Sun for space study.
“When we observe water from an interstellar comet or its subtle ultraviolet signature (OH), we are interpreting notes from another planetary system,” Bordewitz notes.
“This indicates that the components essential for life’s chemical processes are not exclusive to us.”
“All interstellar comets we’ve observed thus far have been unexpectedly intriguing,” remarked Dr. Zexy Shin, a postdoctoral fellow at Auburn University.
“‘Oumuamua was dry, Borisov was rich in carbon monoxide, and now Atlas is revealing water at a distance we didn’t anticipate.”
“Each of these cases is transforming our understanding of how planets and comets form around stars.”
A study detailing the survey findings was published on September 30th in Astrophysics Journal Letter.
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Zexy Shin et al. 2025. Water production rate of interstellar object 3I/ATLAS. APJL 991, L50; doi: 10.3847/2041-8213/ae08ab
The bright area represents the comet’s core, which consists of a dense mixture of ice, rock, and dust. Typically, the nucleus is enveloped in a cloud of gas and dust known as a coma.
Since being discovered in July, Comet 3i/Atlas has captivated both astronomers and space enthusiasts. There have been intriguing theories suggesting it could be alien technology or a spacecraft, though no scientific backing exists for these ideas.
The comet is not stationary.
Researchers tracking its trajectory project that the comet will make its closest approach to the sun around October 30, as its orbit navigates through the inner solar system in the following weeks.
NASA has stated that 3i/Atlas poses no risk to Earth, maintaining a distance of about 170 million miles during its pass.
However, its near pass of Mars provided a unique observational opportunity.
The ExoMars Trace Gas Orbiter, jointly run by the ESA and Russia’s Federal Space Agency, directed its cameras at the comet for approximately a week starting October 1, officials from ESA noted. At that point, 3i/Atlas was roughly 18.6 million miles from the spacecraft.
Despite this, the orbiter’s instruments are primarily designed for imaging the Martian surface rather than distant objects, as explained by Nick Thomas, principal investigator for the imaging system.
“This posed a significant challenge for our instruments,” he stated in a statement. “Comets are approximately 10,000 to 100,000 times less dense than typical targets.”
Other interstellar visitors to our solar system include Oumuamua in 2017 and 2i/Borisov in 2019.
ESA emphasized, “All celestial bodies in our solar system share a common origin, but interstellar comets are unique outsiders, providing insights into the formation of distant worlds.”
As 3i/Atlas travels through our solar system, astronomers are eager to analyze its size and physical characteristics. Earlier this year, it was visible through ground-based telescopes, but it’s currently too close to the sun for observation. It is expected to reappear on the opposite side of the sun by early December, according to NASA.
NASA is tracking 3i/Atlas with the Hubble Space Telescope and plans additional observations in the upcoming months. The James Webb Space Telescope, Spherex Space Observatory, Parker Solar Probe, and the Exoplanet Survey Satellite are among the instruments hoping to catch a glimpse of the comet.
A photo taken recently by the Saturday camera captured streaks of light, leading to speculation online that it could be Comet 3i/Atlas. However, NASA has not confirmed this, and their public information office is currently closed due to the government shutdown.
ESA’s Mars Express spacecraft did focus its camera on the comet as it passed, although further analysis will be required to distinguish interstellar objects from the gathered data.
Following 1i/oumuamua and 2i/borisov, 3i/atlas is the third object and has been confirmed as the second comet originating from outside the solar system.
This image from the Gemini North Telescope Multi-Object Spectrometer (GMOS-N) depicts the interstellar comet 3i/Atlas. Image credits: International Gemini Observatory/Noirlab/NSF/Aura/K. Meech, Ifa&U. Hawaii / Jen Miller & Mahdi Zamani, Noirlab.
The comet 3i/Atlas was identified on July 1, 2025, by the Asteroid Land Impact Trastor Alt System (ATLAS), a project supported by NASA.
Also referred to as C/2025 N1 (ATLAS) and A11PL3Z, the comet is approaching from the direction of Sagittarius.
Its orbit is the most dynamically extreme among the objects documented within the solar system.
“While aliens may not be the first to engage with us, 3i/Atlas has much to teach us, as it is merely the third recorded interstellar entity to traverse our solar system,” stated Jacqueline McClary, an astronomer at Northeastern University.
“All comet-like interstellar bodies are unique in that they are the only ones that have provided us with physical observations coming from outside our solar system. They serve as messengers from afar.”
“Given how rare it is to detect interstellar objects within our solar system, each discovery is distinct,” remarked Adina Feinstein, an astronomer at Michigan State University.
“3i/Atlas presents an opportunity to examine other solar systems closely, without the necessity of traveling to them.”
From the moment 3i/Atlas was observed, it was evident that it deviated from typical comet behavior. Initially, it appeared to emit an unusual light.
Comets are generally very dark, which makes them challenging for astronomers to detect initially.
As they near the sun, solar radiation prompts volatile compounds and ice to sublimate from their surfaces.
This process leads to the formation of a coma, which ultimately evolves into the iconic tail associated with comets across the night sky.
“Jupiter is positioned 5 AU from the Sun, and most comets need to approach closer for solar radiation to generate enough intensity to form this melted tail,” Dr. McClary said.
“Comet 3I/Atlas developed its coma at a considerably greater distance than typical, remaining beyond Jupiter’s orbit.”
3i/Atlas began to emit light far from the sun, prompting initial speculation that it could be an extraterrestrial spacecraft. What else could emit light so rapidly?
However, later observations suggested that it not only possesses a comet-like tail but is also rich in carbon dioxide.
The NASA/ESA/CSA James Webb Space Telescope has ultimately unveiled that comets are remarkable for attributes beyond their interstellar heritage.
Not only was it composed primarily of carbon dioxide, but it also exhibited an extraordinary ratio of carbon dioxide ice to water ice, the best ever documented.
This discovery allows for insight into the conditions that prevail in other solar systems and how such systems were initially formed.
“Clearly, the parent system of 3i/Atlas may have had a wealth of carbon dioxide, or perhaps a unique radiative process occurred that led to the depletion of other materials, leaving abundant carbon dioxide,” Dr. McClary remarked.
“By understanding the composition of this comet and comparing it with other interstellar comets, we gain insight into solar system formation across different environments.”
The precise origin of 3i/atlas remains elusive.
“It likely hails from the Milky Way’s bulge, but pinpointing its exact source will be challenging,” Dr. McCleary commented.
“For it to have escaped its parent solar system, the comet must have undergone a gravitational disturbance that altered its trajectory, setting it on its current path into the solar system.”
Nevertheless, scientists have gained a more intricate understanding of the comet, having observed it crossing Jupiter’s orbit since October, elucidating more about its characteristics.
The Juno satellite orbiting Jupiter is ideally suited to observe these interstellar visitors.
“We may be able to observe this comet with remarkable clarity. It could prove particularly intriguing as it nears the sun, causing significant carbon dioxide vaporization, so we can assess what remains,” Dr. McClary stated.
Gaining more knowledge about 3i/Atlas assists not only in comprehending the nature of other solar systems, but also in exploring the conditions under which sentient life might arise, given the uniqueness of our solar system.
“This serves as a window into the primitive materials of other solar systems, which is invaluable for refining models of solar system formation,” Dr. McCullilia said.
“Is our solar system common or rare? It appears to be relatively uncommon, offering us a way to quantify its uniqueness.”
“Investigating other solar systems places humanity in a broader context,” Dr. Feinstein remarked.
“One of the most profound questions we face is, are we alone in the universe? Each NASA mission brings us a step closer to answering this monumental question.”
“Capturing numerous observations of these interstellar objects, especially as they approach the sun, is crucial for understanding their behaviors,” noted John Noonan, an astronomer at Auburn University.
“These interstellar objects may not have been significantly warmed in millions, if not billions, of years, making it fascinating to study how they react to early thermal exposure.”
Astronomers utilized a Gemini Multi-Object Spectrometer (GMO) at the Gemini South Telescope, part of the NSF’s International Gemini Observatory in the Chilean Andes, to capture new multi-color images of the interstellar comet 3i/Atlas.
This image of 3i/Atlas was captured by the Gemini Multi-Object Spectrograph (GMO) on August 27, 2025 at the Gemini South Telescope. Image credit: International Gemini Observatory / NSF / AURA / Shadow The Scientist / J. Miller Array / M. M. Rodriguez, nsf/crask of rects Anchorage & Noirlab/M. Zamani, NSF’s Noirlab.
3i/Atlas was identified on July 1, 2025, by a NASA-supported Atlas (Asteroid Ground Shock Last Alert System) Survey Telescope in Riojartad, Chile.
The comet is anticipated to approach the Sun at a distance of 1.4 AU (210 million km, or 130 million miles) around October 30, 2025.
The latest images from Gemini/GMOS reveal a broad coma and tail extending roughly 1/120th of a degree across the sky, away from the Sun.
These features appear significantly more pronounced compared to earlier images of the comet, indicating that 3i/Atlas is becoming increasingly active as it traverses the inner solar system.
Recent observations also imply that the dust and ice from the comet closely resemble those of solar comets, suggesting a commonality in the processes that govern the formation of planetary systems around other stars.
“As 3i/Atlas journeys back into the depths of interstellar space, these images serve as both scientific milestones and enigmatic clues,” states Dr. Karen Meech, an astronomer from the Institute of Astronomy at the University of Hawaii.
“They remind us that our solar system is merely a fragment of a vast, dynamic galaxy, where even transient visitors can leave a lasting impact.”
Alongside capturing a stunning image, the primary scientific aim of the observation session was to obtain the comet’s spectrum, which corresponds to the wavelengths of the emitted light.
The resulting spectra provide critical insights into the composition and chemistry of the comet, enabling scientists to understand its changes as it navigates through the solar system.
“The main goal was to observe the color of the comet to glean information about the composition and size of the coma dust particles, as well as to obtain the spectrum for direct chemical analysis,” noted Dr. Mace.
“We were thrilled to witness the growth of the comet’s tail and to see our first hints of chemistry from the spectrum, indicating particle changes since earlier Gemini observations.”
“These observations yield both awe-inspiring visuals and invaluable scientific data,” asserts Dr. Bryce Bolin, a researcher at Eureka Scientific.
“Each interstellar comet acts as a messenger from another stellar system, and by examining its light and color, we can begin to appreciate the diversity of worlds beyond our own.”
Infrared images of 3I/Atlas taken by the James Webb Space Telescope
NASA/James Webb Space Telescope
3I/Atlas, an interstellar visitor, is noted for being one of the most carbon-rich comets observed, suggesting a formation in an environment vastly different from our solar system.
Since July, astronomers have been monitoring 3I/Atlas. While many findings indicate it resembles typical comets, several peculiar features hint at a more exotic origin, including the emission of water gas at distances from the sun typically unobserved in solar system comets.
Martin Codinner from NASA’s Goddard Space Flight Center in Maryland, along with his team, has utilized the James Webb Space Telescope to capture some of the most intricate observations of the comet.
Codinner’s team studied 3I/Atlas in early August, when they were approximately three times the distance from the sun compared to typical comets. At this distance, temperatures rise enough for water to transition from ice to gas, resulting in comets usually generating water vapor and dust, known as a coma.
However, their findings revealed that the coma of 3I/Atlas contains a significantly higher amount of carbon dioxide relative to water, with an 8:1 ratio. This is 16 times more than what is generally seen in other comets from our solar system at this distance from the Sun.
High carbon dioxide levels could imply that comets formed in planetary systems where carbon dioxide ice is more prevalent than water ice, suggests Matthew Genge from Imperial College London. “This may indicate a fundamental difference in planetary system formation compared to ours,” Genge adds.
When planetary systems initially form, there are differing quantities of dust, gas, and water vapor found at varying distances from stars. Over time, stars expel gas, leaving behind solid materials. If the progenitor star of 3I/Atlas expelled water vapor from locations where comets developed earlier than in our solar system, it could account for its unique composition, Genge articulates.
The scarcity of water vapor may also be attributed to previous close encounters with other stars, Genge notes. Codinner offers that water could be concealed deep within the comet’s crust, thus insulated from higher temperatures, which is indeed unusual.
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Hubble Space Telescope Image of Interstellar Comet 3i/Atlas. The telescope tracked the comet, causing background stars to appear as streaks.
NASA, ESA, David Jewitt (UCLA)/Joseph DePasquale (STScI)
The telescope’s observations of the Interstellar Comet 3i/Atlas have shown it resembles a comet found beyond our solar system. Intriguing aspects, like the substantial amounts of water detected even far from the sun, may shed light on the ancient stellar system from which it originated.
Objects from other solar systems that pass through ours are extremely rare. Discovered in July, 3i/Atlas is the third such interstellar visitor, following Oumuamua in 2017 and Borisov in 2019. Remarkably, its visit has only been a few months long.
Scientists speculate that its high speed may indicate that it originates from a star system billions of years older than our own. Initial estimates suggested it has a diameter of approximately 20 kilometers, but details about the extensive plume of water and gas remain limited.
Toni Santana Ross from the University of Barcelona and colleagues have utilized ground-based telescopes to observe the comet and its tail, finding it contains moderate amounts of dust. Notably, the dust appears to increase as the comet approaches the sun, mirroring patterns seen in comets from our outer solar system. “It’s a typical object; there’s nothing particularly strange about it,” states Santana Ross.
Astronomers have also monitored comets via space. Researcher collaborating found that the Hubble Space Telescope might estimate the comet’s size between 320 meters and 5.6 kilometers, and it likely started off much smaller.
Comets usually contain ice, which vaporizes as they near the sun, creating water vapor in their tails. Utilizing the Neil Gehrels Swift Observatory Satellite, Zexi Xing from Auburn University has detected water in the comet’s tail located significantly farther from the sun than is typical for comets. The amount of water detected suggests that about 20% of the comet’s surface is responsible for this production, exceeding typical solar system comet proportions.
Such prolific water generation may indicate that 3i/Atlas originates from a star system much older than ours, hypothesizes Cyrielle Opitom at the University of Edinburgh. This is due to older stellar systems generally having higher water content compared to other molecules. “It might be that because it formed earlier, it retains more water than other molecules, but it’s premature to reach a conclusion,” she remarks.
Astronomers are also scouring historical data to determine if the telescope mistakenly detected a comet. Adina Feinstein and her team at Michigan State University have found that the transit exoplanet survey satellite (TESS) was operationally searching for planets around other stars and incidentally captured a comet between May 7 and June 3. “It just happened that we were observing the exact region where 3i/Atlas was at that moment,” says Feinstein.
The comet was found to be surprisingly bright at that time, suggesting it was releasing significant amounts of water or gas even at considerable distances from the sun. “We didn’t detect transits in regions of our solar system where water would typically start to react,” highlights Feinstein.
In this distant region, the likelihood of finding water is low, with gases such as carbon monoxide and carbon dioxide being more common, according to Opitom. “This is a pattern seen in comets from our solar system; they can exhibit activity at much greater distances due to these volatile materials.”
Yet, the fact that it was active so far from the sun could indicate that this comet has not been significantly exposed to starlight throughout its life, notes Matthew Jenge from Imperial College London.
“What this implies is that this comet was ejected from the fringes of another solar system,” Genge describes. While the exact cause of its ejection is uncertain, it’s possible that gravitational forces from a nearby star could have set it on a trajectory towards us, he explains.
Opitom mentions that the James Webb Space Telescope has recently conducted its observations and that astronomers will analyze the data in the upcoming weeks, promising more insights into 3i/Atlas soon.
As comets approach their closest point to the sun in October, astronomers will have the opportunity to measure the gases they emit. This will provide important insights not only into the characteristics of the comet itself but also into the composition of the molecules in its active tail, which may reveal details about the formation of 3i/Atlas, according to Opitom.
Similar to previous interstellar objects, speculations about potential alien technology exist, but Santana Ross has found no supporting evidence. “If you take a holiday photo and see something tall with a long neck and four legs, you might think of it as an alien, but it’s most likely a giraffe,” he quips. “There’s no reason to believe this is anything unusual or evidence of something extraordinary.”
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Recent analysis of new images from the NASA/ESA Hubble Space Telescope reveals that the nucleus of 3i/Atlas measures between 320 m (1,000 ft) and 5.6 km (3.5 miles).
Hubble captured this image of 3i/Atlas, which was located 446 million km (277 million miles) from Earth on July 21, 2025. Image credits: NASA/ESA/David Jewitt, UCLA/Joseph Depasquale, Stsci.
3i/Atlas was discovered on July 1, 2025, by the Asteroid Land Impact Trastor Alt System (ATLAS) funded by NASA.
Its orbit is the most dynamically extreme among recorded solar system objects.
New observations from Hubble have provided astronomers with a more precise estimation of the comet’s solid icy nucleus size.
“The maximum diameter of the nucleus is 5.6 km, but it averages around 320 m,” stated David Jewitt, an astronomer from UCLA, along with his colleagues.
“Hubble’s images offer tighter constraints on the nucleus’s size compared to earlier ground-based measurements, although the solid core of the comet is not currently visible directly even with Hubble.”
“Data from other NASA missions, like Webb, TESS, Neil Gehrels Swift Observatory, and WM Keck Observatory, will further enhance our understanding of comets, including their chemical composition.”
Hubble also detected indications of dust plumes ejected from the sun-warmed side of the comet, along with dust tails drifting away from the nucleus.
The new findings indicate a dust loss velocity that aligns with the first comet observed at roughly 480 million km (300 million miles) from the Sun.
This behavior closely resembles the characteristics of a previously seen sun-bound comet observed within our solar system.
A notable difference is that this interstellar visitor originates from planetary systems beyond our Milky Way galaxy.
3i/Atlas speeds through the solar system at an astonishing rate of 209,000 km (130,000 miles) per hour, marking the highest speed ever recorded for visitors to our solar system.
This remarkable velocity indicates that comets have been traversing interstellar space for billions of years.
The gravitational pull from countless stars and nebulae has contributed to its increased speed.
The longer 3i/Atlas journeys through space, the faster it moves.
“No one knows the origin of this comet; it’s like catching a glimpse of a bullet for a thousandth of a second,” Dr. Jewitt observed.
“You can’t accurately trace that back to determine where you commenced your path.”
“This latest interstellar traveler represents a previously undetected group of objects, enriching the narrative that has gradually unfolded.”
“This achievement is now possible due to the powerful Sky Survey capability we previously lacked. We’ve reached a new milestone.”
NASA’s Juno spacecraft may be tasked with intercepting interstellar objects
NASA/JPL-Caltech
Interstellar objects passing through our solar system make a brief journey around the sun before heading back into deep space. While astronomers can capture images of comet 3i/Atlas traversing our universe, is there a possibility of intercepting this object?
Researchers globally are investigating several strategies, including repurposing European Space Agency (ESA) missions and rerouting existing NASA endeavors to intervene. However, the task is complicated by the comet’s speed of 60 km/sec and the limited preparation time available.
One notable proposal comes from Avi Loeb at Harvard University, who suggests that the interstellar object “Umuamua is akin to an alien spacecraft; I made a similar assertion regarding 3i/Atlas.” Loeb and his team have published a paper, which, despite not being peer-reviewed, indicates that NASA’s Juno spacecraft could adjust its orbit around Jupiter to rendezvous with 3i/Atlas on March 14th next year.
Nonetheless, this idea faces challenges. Mark Burchell from the University of Kent emphasizes the aging spacecraft’s limitations. Launched in 2011, Juno was initially slated to end its mission with a collision into Jupiter’s surface in 2021, which has been delayed until September this year. It has already experienced two technical issues this year, both resolved by engineers.
“The current orbit allows for closer views of Jupiter and a pass by Io [Jupiter’s moon] in 2023. By 2024, it will be exposed to significant radiation, which is unsurprising given the performance anomalies observed that necessitate a restart,” Burchell explains. “If those modifications are successful and the instruments function properly, there might be valuable data to acquire.”
In a post on X,Jason Wright from Penn State has also voiced skepticism regarding this concept, highlighting that the spacecraft has limited fuel and systematic engine issues.
Another potential avenue to observe 3i/Atlas closely is through the ESA’s Jupiter Ice Moon Explorer (Juice). Luca Conversi from ESA mentions that they are considering this possibility. “We acknowledge this valuable opportunity and are currently assessing the technical feasibility. However, we can’t divulge too much at this stage,” Conversi states.
Despite Juice being closer to 3i/Atlas than Earth, it cannot alter its course towards the comet. “I’m uncertain if redirecting it to a comet is practical. Astrodynamics is far more complex than depicted in science fiction films, and altering a spacecraft’s trajectory is quite challenging,” comments Conversi.
Presently, several spacecraft, including Mars Reconnaissance Orbiter and Mars Odyssey, are in orbit around Mars and nearing the end of their operational lifespans. Research conducted by Michigan State University and colleague Atsuhiro Yaginuma suggests that while this method has advantages, it’s unclear whether these spacecraft possess sufficient fuel for such a journey.
The ESA is developing another mission aimed at improving the chances of approaching interstellar objects in the future. The Comet Interceptor spacecraft, scheduled for launch in 2029, is set to await the discovery of comets or interstellar objects that can be targeted at a stable position between Earth and the Sun, facilitating exploration. These missions are rare, as scientists often do not know what the target will be or its appearance timeline.
Colin Snodgrass at the University of Edinburgh, who serves as the deputy lead of the Comet Interceptor, elaborates that this mission would “require a bit of additional maneuverability” to effectively intercept fast-moving objects like 3i/Atlas. For these swift visitors, he suggests a broader mission with a streamlined payload. “If the goal is simple speed, minimize non-essential equipment and prioritize fuel mass,” he advises.
Another future concept involves deploying small satellites in large orbits monthly. “This would distribute them across Earth’s orbit,” Snodgrass explains. “At any time, one of them could return to Earth and leverage gravity to navigate to interesting locations.”
Astrometric endeavors, such as the legacy investigation of space and time, could quickly enhance our understanding of the frequency of these objects entering our solar system, improving prior warnings about their arrival. “When they are moving rapidly, timely notifications can make a significant difference. Instead of providing alerts months ahead of perihelion, having earlier warnings will significantly impact our response,” Snodgrass remarks.
Astronomers utilizing the Gemini North telescope at NSF’s International Gemini Observatory have observed the interstellar comet 3i/Atlas as it passes through our cosmic neighborhood.
This image from the Gemini North Telescope Multi-Object Spectrometer (GMOS-N) showcases the interstellar comet 3i/Atlas. Image credits: International Gemini Observatory/Noirlab/NSF/Aura/K. Meech, Ifa&U. Hawaii / Jen Miller & Mahdi Zamani, Noirlab.
Interstellar objects are those that emerge from and traverse beyond our solar system.
Ranging from several meters to a few kilometers in size, these cosmic fragments are remnants from the formation of the host star’s planetary system.
As they orbit their stars, interactions with the gravitational pull of nearby planets and stars can eject them into interstellar space, allowing them to traverse other solar systems.
Studying interstellar visitors provides critical insights into distant star systems.
They carry valuable information about chemical elements, including their formation timelines and locations, offering scientists glimpses into the formation of planetary systems throughout the history of the Milky Way galaxy.
3i/Atlas marks the third interstellar object discovered, following 1i/Oumuamua in 2017 and 2i/Borisov in 2019.
Astronomers suspect that numerous interstellar objects might regularly pass through our solar system, but capturing them is challenging as they are only visible when telescopes are oriented correctly at the right time.
Multiple teams worldwide utilize various telescopes to monitor 3i/Atlas during its brief visitation, enabling them to collectively assess its key properties.
While many aspects remain unknown, 3i/Atlas is already recognized as distinct in comparison to 1i/Oumuamua and 2i/Borisov.
Previous observations suggest that 3i/Atlas could have a diameter of up to 20 km (12 miles).
New comets typically exhibit highly eccentric orbits, which define how much the object’s path deviates from a perfect circle.
An eccentricity of 0 indicates a circular orbit, while 0.999 signifies a highly elongated ellipse.
Objects with an eccentricity greater than 1 follow paths that do not loop around the Sun and come from, then return to, interstellar space.
The eccentricity of 3i/Atlas is recorded at 6.2, classifying it as a highly hyperbolic interstellar object.
In contrast, “Oumuamua’s” eccentricity was around 1.2, and Borisov’s was about 3.6.
As of now, 3i/Atlas resides in Jupiter’s orbit, approximately 465 million km (290 million miles) from Earth and 600 million km (370 million miles) from the Sun.
On December 19, 2025, it will come within roughly 270 million km (170 million miles) of Earth, posing no threat to our planet.
The closest approach to the Sun will occur around October 30, 2025, at a distance of 210 million km (130 million miles).
During this close approach, it is expected to travel at about 25,000 km (15,500 miles) per hour.
The latest image of 3i/Atlas was obtained using the Gemini North Telescope Multi-Object Spectrometer (GMOS-N).
“The sensitivity and scheduling precision of the International Gemini Observatory played a critical role in observing this interstellar wanderer,” remarked Martin Still, NSF Program Director at the International Gemini Observatory.
“We eagerly anticipate the wealth of new data and insights as this object warms in sunlight before continuing its cold, dark journey through interstellar space.”
Research conducted by astronomer Matthew Hopkins and his team at Oxford University suggests that 3i/Atlas, the second interstellar comet discovered near our solar system, may have been on its trajectory over 3 billion years ago.
Top view of the Milky Way displaying the predicted orbits of our Sun and 3i/Atlas. Comets are represented by dashed red lines, while the sun is indicated by a dashed yellow line. The comet’s route to the outer thick disc is mostly clear, whereas the sun remains close to the nucleus of the galaxy. Image credit: M. Hopkins / Otautahi Oxford Team / ESA / Gaia / DPAC / Stefan Payne-Wardenaar / CC-SA 4.0.
“All comets formed alongside our solar system, like Halley’s comets, are up to 4.5 billion years old,” Dr. Hopkins explained.
“In contrast, interstellar visitors can be significantly older. Our statistical analyses indicate that 3i/Atlas is very likely to be the oldest comet we’ve observed thus far.”
Unlike 1i/Oumuamua and 2i/Borisov, the two previous interstellar objects that passed through our solar system, 3i/Atlas appears to be on a more inclined path through the Milky Way.
A recent study forecasts that 3i/Atlas is likely to be rich in water ice, as it probably formed around the star of the ancient, thick disc.
“This is an aspect of the galaxy that we’ve never encountered before,” said Chris Lintot, a professor at Oxford University and host of The Sky at Night.
“I believe there is a two-thirds chance that this comet predates the solar system and has been drifting through interstellar space ever since.”
As it nears the Sun, the heat from sunlight activates 3i/Atlas, generating a coma and tail composed of steam and dust.
Initial observations indicate that the comet is already active and may even be larger than any of its interstellar predecessors.
If this is validated, it could influence the detection of similar objects by future telescopes, such as the upcoming Vera C. Rubin Observatory.
Furthermore, it could offer insights into the role that ancient interstellar comets play in the formation of stars and planets throughout the galaxy.
“We’re in an exciting phase. 3i/Atlas is already displaying signs of activity,” remarked Dr. Michele Bannister, an astronomer at the University of Canterbury.
“The gases we might observe in the future, as 3i/Atlas is heated by the Sun, will help us evaluate our models.”
“Some of the world’s largest telescopes are currently monitoring this new interstellar entity. One of them may make a significant discovery!”
The astronomer utilizing ESO’s Extremely Large Telescope (VLT) has unveiled a new image of 3i/Atlas, marking it as the third interstellar object documented.
This VLT/FORS2 image, captured on July 3, 2025, depicts interstellar comet 3i/Atlas. Image credit: ESO/O. Hainaut.
3i/Atlas was identified a week ago by the NASA-supported Atlas Survey Telescope in Riojartad, Chile.
Commonly referred to as C/2025 N1 (ATLAS) and A11PL3Z, this comet is approaching from the direction of Sagittarius.
“In contrast to objects within the solar system, its highly eccentric hyperbolic orbit indicates its interstellar origin,” ESO astronomers stated.
Currently, 3i/Atlas is approximately 4.5 AU (670 million km, or 416 million miles) away from the Sun.
Interstellar objects pose no danger to Earth, maintaining a distance of at least 1.6 AU (240 million km, or 150 million miles).
Around October 30, 2025, it will make its closest approach to the Sun at a distance of 1.4 AU (210 million km, or 130 million miles).
“In the VLT time-lapse, you can observe 3i/Atlas moving to the right over approximately 13 minutes,” the astronomer remarked.
“These observations were gathered using FORS2 equipment at the VLT on the night of July 3, 2025, just two days post-discovery of the comet.”
“At the conclusion of the video, all frames are compiled into a single image.
“However, this record will not endure as the comet approaches Earth and becomes less visible.”
“As it currently traverses more than 600 million km from the Sun, 3i/Atlas is heading towards the inner solar system, expected to reach its closest approach to Earth in October 2025,” they noted.
“During that time, 3i/Atlas will be obscured by the Sun, but observations should resume in December 2025.
“Telescopes globally, including the VLT, will persist in monitoring this extraordinary celestial visitor to gather more insights into its structure, composition, and origin.”
3i/Atlas is only the third celestial object ever detected, following the interstellar asteroid 1i/Oumuamua in 2017 and the interstellar comet 2i/Borisov in 2019.
Images of 3i/Atlas captured by the Atlas telescope. Image credit: University of Hawaii.
The 3i/Atlas is currently about 670 million km (420 million miles) from the Sun and is expected to make its closest approach in October 2025, moving just within Mars’ orbit.
It is estimated to be up to 20 km (12 miles) in diameter, traveling at around 60 km (37 miles) per second relative to the Sun.
This comet poses no threat to Earth, remaining within a distance of 240 million km (150 million miles), which is more than 1.5 times the distance between the Earth and the Sun.
3i/Atlas is an active comet. As it approaches the Sun, the heat causes frozen gases to turn into vapor, releasing dust and ice particles into space and initiating the formation of a glowing coma and tail.
However, by the time it reaches its closest point to Earth, it will be obscured by the Sun. It is expected to be visible again by early December 2025, providing astronomers with an opportunity for further research.
“Finding possible interstellar objects is extremely rare, and it’s thrilling to see the Atlas telescope catch this asteroid,” said a representative.
“These interstellar visitors allow us to glimpse something intriguing from solar systems beyond our own.”
“3i/Atlas is the largest ever observed, yet numerous such objects traverse our inner solar system each year.”
“The likelihood of an impact with Earth is minimal, occurring less than once in 10 million years, but Atlas is consistently scanning the sky for potentially hazardous objects.”
Astronomers across Hawaii, Chile, and other nations are tracking the comet’s progression.
They seek to learn more about the composition and behavior of this interstellar visitor.
“It is precisely their foreign nature that makes interstellar objects like 3i/Atlas so remarkable,” an ESA astronomer stated.
“While all planets, moons, asteroids, comets, and life forms in our solar system share a common origin, our interstellar visitors are genuine outsiders.”
“They are remnants from other planetary systems, providing clues about the formation of worlds beyond our own.”
“It may take thousands of years before humans visit planets in another solar system, and interstellar comets give us the chance to stimulate our curiosity as we interact with something from another world.”
“These icy nomads offer a rare, tangible link to the broader galaxy. This material is fundamentally different from our own and is formed in unique environments.”
“Visiting such objects connects humanity with the universe on a grander scale.”
Following the interstellar asteroid 1i/Oumuamua and comet 2i/Borisov, 3i/Atlas is the third identified object and the second comet from outside the solar system.
This image was captured on July 2, 2025, with an Itemescope.net T72 telescope in Riojartad, Chile, depicting the interstellar comet 3i/Atlas. Image credit: Filipp Romanov/CC by-sa 4.0.
3i/Atlas was discovered by a NASA-funded research telescope dedicated to the Atlas (Asteroid Surface Impact Last Altar System) project on July 1, 2025, in Riojartad, Chile.
The interstellar comet approached from the direction of constellations and is currently about 670 million km (420 million miles) away.
“Since the initial report, pre-discovery observations have been gathered from archives of three different Atlas telescopes globally and from Zwicky’s transitional facility at Palomar Observatory in San Diego County, California,” a NASA astronomer wrote in a statement.
“These pre-discovery observations date back to June 14th, 2025.”
Known as 3I/ATLAS, C/2025 N1 (ATLAS), and A11PL3Z, it currently measures approximately 4.5 AU (670 million km, or 416 million miles) away.
Comets pose no threat to Earth, maintaining a safe distance of at least 1.6 AU (240 million km, or 150 million miles).
It is predicted to reach its closest approach to the Sun around October 30th, 2025, at a distance of 1.4 AU (210 million km, or 130 million miles).
Its size and physical characteristics are being studied by astronomers worldwide.
This diagram illustrates the trajectory of 3i/Atlas as it traverses the solar system. Image credit: NASA/JPL-Caltech.
If the brightness of 3i/Atlas is attributed to reflecting sunlight at a typical albedo of 10%, its diameter would be approximately 100-200 times greater than the estimated length of 20 km for Oumuamua and about 50-100 times larger than the estimated size of Borisov.
“If all three objects are indeed rocky, the mass of 3i/Atlas is more than 10 million times greater than that of Oumuamua and at least 100,000 times the core mass of Borisov.”
“This is remarkable because we expect high-mass objects to be exceedingly rare.”
“Based on data from the major asteroid belts of the solar system, we would expect millions of objects like Oumuamua for each object with the mass of 3i/Atlas.”
3i/Atlas should remain visible to ground telescopes until September 2025.
It is anticipated to reappear on the opposite side of the Sun by early December, enabling further observations.
“Based on its trajectory, 3i/Atlas seems to enter in a retrograde orbit, inclined at 175 degrees relative to Earth’s orbital plane from the thin disc of stars in the Milky Way,” explains Professor Roeb.
“In the upcoming months, we will gain further insights into the properties of 3i/Atlas based on data from various ground-based telescopes and the NASA/ESA/CSA James Webb Space Telescope, including the NSF/DOE Vera C. Rubin Observatory in Chile.”
Comet 3i/Atlas is the third interstellar object detected in the solar system
E. Guido, M. Rocchetto, J. Ferguson
Interstellar objects have been observed speeding through the solar system, prompting both amateur and professional astronomers globally to direct their telescopes toward them, refining their orbital models to confirm their status as visitors from other stars.
The comet was initially designated A11PL3Z and marks the third documented interstellar object. The first, ‘Oumuamua, was identified in October 2017, shortly after its closest approach to Earth. Its bizarre acceleration sparked numerous theories, including the possibility that it might be an alien spacecraft. The second interstellar object, Comet Borisov, was discovered in 2019, allowing for more extensive observations early in its journey through the solar system.
The A11PL3Z was first detected by NASA’s Asteroid Terrestrial Impact Last Alert System (ATLAS). Earlier images of the object, once overlooked, were identified in data collected on June 14. New observations are underway in Chile and beyond through the Deep Random Survey. The Minor Planet Center—charged with the observation and reporting of such entities—has now officially named it 3I/ATLAS, acknowledging both its classification as the third interstellar object and the discoverers.
The object measures approximately 20 km wide and is estimated to move at around 60 km per second, gradually accelerating due to the sun’s gravitational pull. By October, it will reach its closest point to the Sun, passing within two astronomical units (twice the distance from Earth to the Sun) before swinging away and exiting our solar system.
The anticipated trajectory of 3i/Atlas marks its position as only the third interstellar object to be recorded in the solar system
CSS, D. Rankin
This creates a limited window for studying 3i/Atlas, although its visibility offers more time for observation compared to other interstellar entities. “They move through the solar system at astonishing speeds,” states Mark Norris from the University of Central Lancashire, UK. “It’s a race against time to learn as much as we can about them.”
Unfortunately, the technology needed to launch missions to intercept and investigate these celestial visitors remains out of reach, according to Norris. “Even if we started today, it would be too late,” he concludes. However, this may evolve soon, as the European Space Agency (ESA) aims to deploy a comet interceptor mission into space in 2029, where it will await encounters with newly discovered comets and interstellar bodies.
For now, astronomers must depend on existing telescopes to observe 3i/Atlas from a distance. “As we can track it until the end of the year, we have sufficient time to refine its trajectory, and there’s still time to focus the spectrometer on it,” mentions Richard Moisle. Our team is already eager to pinpoint the earliest possible observations. Everyone is highly enthusiastic and ready for what’s ahead.”
World Capital of Astronomy: Chile
Explore the breathtaking astronomical sites in Chile. Visit advanced observatories and marvel at the breathtaking clear night skies.
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