Sungrazer C/2024 S1 ATLAS broke apart at perihelion.
Alas, a ‘Great Halloween Comet’ was not to be. The Universe teased us just a bit this month, with the potential promise of a second naked eye comet in October: C/2024 S1 ATLAS. Discovered on the night of September 27th by the Asteroid Terrestrial Last-alert impact System (ATLAS) all-sky survey, this inbound comet was surprisingly bright and active for its relative distance from the Sun at the time of discovery. This gave the comet the potential to do what few sungrazers have done: survive a blisteringly close perihelion passage near the Sun.
S1 ATLAS on final solar approach. NASA/ESA/SOHO
But as perihelion day approached yesterday on October 28th, things started to look grim. S1 ATLAS began to resemble a garden variety Kreutz sungrazer more and more. Little more than an icy rumble pile on final approach, the comet went in the inner field of view of the Solar Heliospheric Observatory’s (SOHO) LASCO C2 imager and behind the central occulting disk yesterday morning… and failed to exit.
Comet S1 ATLAS ends its days, as seen via SOHO’s LASCO C2 imager. NASA/SOHO
Perihelion distance (and time of expiry) for the comet was 330,600 miles/532,000 kilometers from the surface of the Sun yesterday, at around 7:30 AM EDT/11:30 Universal Time. Curiously, the final estimates for the comet put its orbital period at 953 years, suggesting that this may not have been its first passage through the inner solar system.
The finale for Comet S1 ATLAS, just hours prior to perihelion. ESA/NASA/SOHO/NRL
The comet gave us a few tell-tale signs that it was under-performing leading up to perihelion. After a brief outburst around its discovery 1.094 Astronomical Units (AU) from the Sun, the comet then faded considerably in early October. The lackluster performance was confirmed as it entered the field of view of SOHO’s LASCO C3 viewer this weekend. Still, its final solar dive put on a good show.
The demise of Comet S1 ATLAS yesterday brought to mind memories from early on in my Universe Today writing career of another great comet that wasn’t: C/2012 S1 ISON. That particular comet met its end on U.S. Thanksgiving Day 2013. The last great surprise for sungrazers was Comet W3 Lovejoy in 2011-2012, which survived a perihelion just 87,000 miles/140,000 kilometers from the surface of the Sun (!), and went on to become a great comet. Another example showing us what is possible was Comet Ikeya-Seki, which survived perihelion 280,000 miles/450,000 miles from the Sun in 1965 and became one of the great comets of the 20th century.
Light curve magnitude comparisons of comets Ikeya-Seki, W3 Lovejoy and S1 ATLAS in the lead up to their respective perihelia. Credit: Jakub Cerný
Astronomer Heinrich Kreutz discovered the existence on the Kreutz family of sungrazing comets in the 1890s. The earliest documented report of a sungrazer was from Greece by Aristotle and contemporary historian Ephorus in 371 BC. Prior to 1979, only nine confirmed sungrazers were known of… the launch of the joint NASA European Space Agency’s SOHO mission in 1995 changed the game considerably. Now, SOHO’s sungrazer tally after over a quarter of a century in space is 5,065 comets and counting. It turns out, we were still missing lots of what was passing through the inner solar system, all this time.
Last week, the NOAA revealed the successor for SOHO’s coronagraph aboard its GOES-19 satellite. The CCOR-1 (Compact Coronagraph) should start releasing public images in early 2025.
This comes as the ‘other’ October comet, C/2023 A3 Tsuchinshan-ATLAS fades from view. A3 T-ATLAS is now outbound at +6th magnitude in the constellation Ophiuchus. The comet had a decent evening apparition post perihelion a few weeks ago. The spiky ‘anti-tail’ provided an amazing view.
Are there any great comets on tap for 2025? Well, as of writing this, there’s only one comet with real potential to reach naked eye visibility in 2025: Comet C/2024 G3 ATLAS. This comet reaches perihelion 0.094 AU from the Sun on January 13th. G3 ATLAS and ‘may’ top -1st magnitude or brighter.
S1 ATLAS may have joined the ranks of comets that failed to live up to expectations… but you just never know. Its fast-paced story from discovery to demise shows us just how quickly the next bright comet could make itself known. Keep watching the skies: its only a matter of time.