2024 September 30

Interesting new sungrazing comet discovered

Nick James

Update 2024-10-01. The comet has been designated C/2024 S1 (ATLAS) on MPEC 2024-T22 and the section image gallery is here.

Update 2024-10-08. The comet appears to have been discovered in outburst since it started to fade shortly after discovery. It appears to have fragmented.

With all the current excitement about C/2023 A3 (Tsuchinshan-ATLAS) we may have another bright coming along towards the end of October. This is a much smaller object discovered by the ATLAS survey on September 27 and it is still listed on the Possible Comet Confirmation Page (PCCP) as A11bP7I. Even though it is small, Sam Deen on comets-ml noted that  it may become bright since it gets very close to the Sun at its perihelion on 2024 October 28. At present, 3 days after its discovery, we have enough astrometry to be able to define its orbit quite well so we know where in the sky it will be but we don’t have much information on how bright it will become. In any case, if it does become bright, it will be very close to the Sun with observers in the southern hemisphere favoured.

It looks very much as if this comet is a member of  the Kreutz family of sun-grazing comets and the current prediction is that it will get to within 300,000 km of the surface of the Sun on October 28. The most famous member of this family is probably C/1965 S1 (Ikeya-Seki), although a more recent example was C/2011 W3 (Lovejoy). These comets are all thought to have originated from a massive comet that fragmented at a past perihelion. The current orbital elements for A11bP7I based on astrometry processed in Findorb with a constraint of e=1 are set out below. The astrometry has a mean residual of 0.60″ over an arc of 3 days. This is compared with the other two comets in the table below:

At present this comet is around 14th magnitude and it is moving slowly through the constellation of Hydra. An ephemeris for the next few days is here.

The visibility circumstances for this comet are shown in the following plot for latitudes of 60S to 60N. It is a morning object throughout the apparition and much better placed from the southern hemisphere. If it survives perihelion it could be a very nice object in the morning twilight sky for a few days after October 28 but it may also do nothing so, for now, watch this space for further details!