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
