Astronomers Uncover Third Interstellar Object: 3I/ATLAS

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.”

Source: www.sci.news

A11PL3Z: The Interstellar Comet 3i/Atlas Traversing Our Solar System

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.”

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Source: www.newscientist.com