Astronomers photographed the interstellar comet as it made its closest approach to our planet on December 19. The photo captures interstellar comet 3I/ATLAS as it shines in the sky with two tails stretching out into space, as seen in this photograph taken in a remote observatory in Utah. The comet shines brightly in its image as it lingers in space, marking its distance and creation in another star system.
Identified earlier this year by NASA’s Asteroid Terrestrial-impact Last Alert System (ATLAS), 3I/ATLAS is only the third known interstellar object ever observed passing through the Solar System, after ‘Oumuamua in 2017 and comet Borisov in 2019.
Closest Approach And Trajectory
The comet passed Earth at a safe distance of about 270 million kilometres, roughly 1.8 astronomical units, moving at a speed of nearly 68 kilometres per second. Scientists say its sharply hyperbolic orbit confirms that it is not gravitationally bound to the Sun and instead originated in another stellar system.
Although it reached perihelion, its closest point to the Sun, on October 29 at a distance of 1.36 AU, the December 19 flyby marked the most significant moment for observers on Earth. At no point did the object pose any threat, NASA has clarified.
How Image Was Captured
The widely shared image was produced by stacking exposures totalling 74 minutes using a PlaneWave Delta Rho 500 telescope and a high-resolution ZWO camera. This method revealed a bright, active coma surrounding the nucleus, consisting of a straight ion tail created by solar winds, as well as a dust tail trailing behind it. This particular comet was captured in front of the constellation Leo.
Already, the James Webb Space Telescope has found the comet to have high levels of carbon monoxide. This means the comet formed under very cold conditions billions of years ago, possibly around an older star than the Sun. Scientists believe this information can be useful in understanding how comets and planets are formed in other star systems.
Further observations have also detected X-ray emissions from the comet, a phenomenon seen in Solar System comets but never conclusively studied in an interstellar one until now.
After the Earth flyby, 3I/ATLAS is currently on an outward course, with its next significant encounter scheduled near the planet Jupiter in March 2026. Subsequently, it will move beyond the solar planets before leaving the solar system. Although the comet will eventually disappear, scientists say that the observations that can be made during its brief passage by our planet will take years to analyse.