3I/ATLAS will pass at its closest distance from Earth on December 19 at around 4 a.m. UT

3I/ATLAS is currently only three days away from its closest approach to Earth, allowing us to determine the time of its closest approach with great precision. Calculations indicate that it will pass closest to the planet on December 19th at approximately 4:00 AM UT. Currently, 3I/ATLAS has effectively entered a synchronized motion with the planet. Throughout the coming week, from today until December 22nd, the distance between the object and Earth will remain virtually constant, within half a million kilometers (approximately 0.2% of the distance separating them). After this period, the interstellar object will begin to rapidly move away from the planet.

Currently, 3I/ATLAS is the third brightest comet in the sky. Such a high location, however, still offers no chance of seeing the celestial body with the naked eye or simple optical instruments: 3I/ATLAS's current magnitude of approximately 12m completely rules out such a possibility. The body's position in the sky will remain virtually unchanged throughout these days, and although it is far from easily identifiable landmarks like the constellation Ursa Major, it can nevertheless be determined using online star chart apps and by the large stars located in its vicinity—Arcturus, Sirius, and Procyon. The closest star to 3I/ATLAS's position in the sky throughout these days will be Regulus, the "Heart of the Lion," the brightest star in its corresponding constellation. The object's location rises above the horizon at approximately 10–11 pm local time, but more or less acceptable conditions for observation will only arise around 1–2 am and will persist until sunrise.