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New Delhi: The comet 3I/Atlas will be making its closest approach to the Earth on 19 December, which is the best time to directly observe the interstellar visitor. The comet will be visible below the constellation of Leo in the eastward sky. A number of ground and space based astronomical instruments are studying the comet through its journey through the Solar System, as it is considered to be the fragment of an ancient star system, far older than the Solar System. The object will approach no closer than 273 kilometres to the Earth, which is more than 700 times the distance between the Earth and the Moon.

The best time to observe the comet is in the pre-dawn sky. A telescope with an aperture of at least 30 centimetres is recommended to observe the comet. The comet was initially discovered on 1 July 2025 by the ATLAS survey telescope in Chile, that continuously monitors the skies for objects that appear to have changed their luminosities or positions. When discovered, the comet was already within the Solar System, approaching Mars in early October, and then reaching its closest point to the Sun on 29 October. The comet will now approach close to Jupiter in 2026, before leaving the Solar System forever and continuing on its journey through the galaxy.

3I/Atlas has been zipping around the Milky Way for billions of years

The comet was likely ejected from a distant star billions of years ago. NASA’s Hubble Space Telescope measured its icy core as up to seven kilometres wide. The comet is a dirty snowball that is spewing gas and dust as it heats up. The comet has a small coma, and a short tail. The Virtual Telescope Project has scheduled a livestream for 19th December, allowing audiences from around the world to observe the comet in real time. 3I/Atlas is only the third interstellar object known to scientists.