C/2024 G3 (ATLAS) is a long-period, sungrazing comet, which will reach perihelion on 13 January 2025, at a distance of 0.09 AU from the Sun.
It could become the brightest comet of 2025,[4] possibly exceeding apparent magnitude of −3.5. The comet is visible in the southern hemisphere before and after perihelion. It can only be observed in the daytime sky around perihelion in the northern hemisphere.[5]
Observational history
The comet was discovered by the Asteroid Terrestrial-impact Last Alert System (ATLAS) survey on 5 April 2024, in images obtained with a 0.5-m reflector telescope located in Río Hurtado, Chile. The comet at the time was a magnitude 19 object about 4.38 AU (655 million km) from Earth. Further observations indicated it had a diffuse coma about 4.5 arcseconds across and a straight tail.[1]
At the time of discovery, it was assumed that this was a new comet from the Oort cloud, and with its very weak absolute magnitude (H=9), there was very little to no chance that it would survive perihelion.[6][7] But as the orbit was refined it was found to be likely a dynamically old comet, having made close approaches to the Sun before.[8]
By 30 October 2024, the comet had an apparent magnitude of 11.9 per reported observations at the Comet Observation Database (COBS)[9], visible with large telescopes. By mid December 2024 it had brightened to 8th magnitude and was located in Scorpio, visible at dawn in the southern and equatorial regions.[10]
In case of this comet very difficult to predict peak brightness (spread more than 10 mag). G. van Buitenen predicts −4.5 magnitude, accounting for forward scattering, however it will be just 5 degrees from Sun at peak magnitude.[11] After perihelion the comet heads southwards, while in mid northern latitudes will be low, being 2 degrees above the horizon at the end of the civil twilight.[10]
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