Interstellar Object 3I/ATLAS. Credit: NASA/ESA/STScI/D. Jewitt (UCLA)/DePasquale (STScI)
On July 1, 2025, astronomers spotted the third known interstellar object 3I/ATLAS (ISO) as it passed through our Solar System.
Automated systems first detected it, and scientists at the European Space Agency (ESA) quickly began studying it using telescopes in Hawaii, Chile, and Australia. The object, named 3I/ATLAS, has since been observed by several space telescopes, including the NASA/ESA Hubble Space Telescope. On November 30, Hubble observed it again as it approached its closest point to Earth.
Since early November, after 3I/ATLAS reappeared from behind the Sun, scientists have been able to study it in greater detail. As the object warmed up, its comet activity increased, releasing more gas and dust. During the latest observations, Hubble tracked the comet from about 286 million kilometers (178 million miles) away using its Wide Field Camera 3. In about a week, on December 19, it will pass closest to Earth at a distance of 269 million kilometers (167 million miles), nearly 1.8 times farther than the distance between Earth and the Sun.
ESA scientists have been closely watching 3I/ATLAS using nearly all available space missions. These include ESA’s XMM-Newton observatory, JAXA’s X-Ray Imaging and Spectroscopy Mission (XRISM), and the James Webb Space Telescope. When the object passed near Mars in October, ESA also used Mars Express, the ExoMars Trace Gas Orbiter, and the Jupiter Icy Moons Explorer (JUICE) to collect additional data.
The observations confirmed that 3I/ATLAS is a comet, but they also revealed some unusual traits. It contains a high amount of carbon dioxide, very little water, and traces of atomic nickel gas. Its large size and path close to the plane of the Solar System are unusual, though still consistent with known comet behavior.
3I/ATLAS is now heading away from the inner Solar System. It is expected to cross Jupiter’s orbit in the spring of next year and will likely be too distant for Hubble or the James Webb Space Telescope to observe after 2028.
source ESA
Leave A Comment