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A rare interstellar comet named 3I/ATLAS is hurtling through the solar system. It would give astronomers a rare glimpse of material that formed around another star. It is only the third confirmed interstellar object ever detected after ‘Oumuamua’ in 2017 and ‘Borisov’ in 2019, as per experts.
The comet was first detected on July 1, 2025, by the Asteroid Terrestrial-impact Last Alert System (ATLAS) telescope in Chile. The “3I” designation marks it as the third interstellar object ever identified, while “ATLAS” refers to the telescope that spotted it.
NASA later confirmed that the comet is following a hyperbolic orbit, meaning it is not gravitationally bound to the Sun and will leave the solar system after a brief passage.
According to the European Space Agency (ESA), the comet will make its closest pass to Earth on December 19, coming within about 270 million kilometres, a safe distance that poses no threat to the planet.
Latest observations between October 31 and November 4 suggest that the object has shed a significant amount of mass during its encounter with the solar system. It has also shifted its path slightly, showing signs of non-gravitational acceleration, motion not caused just by gravity, according to a report by IFL Science.
A Chinese Mars orbiter has captured rare images of the comet as it passed near the Mars on October 3, the China National Space Administration (CNSA). The pictures were taken by Tianwen-1, China’s ongoing Mars exploration mission, marking the first successful attempt to photograph such a distant and dim interstellar target.
“The Tianwen-1 orbiter successfully observed the interstellar object 3I/ATLAS using its high-resolution camera from a distance of about 30 million kilometres, one of the closest probes to do so… The images clearly show the comet’s distinctive features, consisting of a nucleus and a surrounding coma, with a diameter reaching several thousand kilometers,” the CNSA said in a statement.
Preliminary data suggests that 3I/ATLAS is an active comet composed of volatile materials similar to those found in solar system comets, but altered by long-term exposure to interstellar radiation. As per NASA Planetary Science Division, early spectroscopic readings suggests the presence of carbon dioxide (CO₂) and dust emissions consistent with cometary outgassing behaviour driven by the Sun’s heat .
A study based on James Webb Space Telescope (JWST) observations posted to the preprint server suggested that the comet’s surface appears chemically processed, suggesting it has travelled through the interstellar medium for billions of years, where cosmic rays likely altered its outer layers.
The Hubble Space Telescope has estimated the solid nucleus of 3I/ATLAS to be no larger than 5.6 kilometres across, though the exact size remains uncertain because of the surrounding dust cloud that obscures direct measurements.
The European Space Agency (ESA) observations noted that the comet’s bright coma extends several thousand kilometres, formed by continuous ejection of dust and gas as it nears the Sun.
