Could a New Sungrazer Comet Put on a Show at the End of October?

Could this be the next great comet? To be sure, these words have been said lots of times before. In a clockwork sky, how comets will perform is always the great wildcard. Comets from Kohoutek to ISON have failed to live up to expectations, while others like W3 Lovejoy took us all by surprise. But a discovery this past weekend has message boards abuzz, as an incoming sungrazer could put on a show right around Halloween.

Anatomy of a Sungrazer

The discovery comes to us from the prolific Asteroid Terrestrial-impact Last Alert System (ATLAS), which first spotted the comet on the night of September 27^th. The initial designation of the comet was A11bP7I. The comet now has an official designation: C/2024 S1 ATLAS. This was announced on October 1^st, in the International Astronomical Union’s Central Bureau for Astronomical Telegram’s message 5453.

The highly eccentric hyperbolic orbit of the comet suggests it’s a member of the Kreutz family group of sungrazer comets. Most of these comets are doomed for destruction at perihelion, but there have been a few exceptions over the years. Those sungrazers that have survived have gone on to become great comets.

Could C/2024 S1 ATLAS do the same?

Comet Caveats

Now, a few caveats are in order. Astronomers found S1 ATLAS at +12^th magnitude, 1.094 Astronomical Units (AU) from the Sun. It could well be the case that it simply had an outburst right when it was first spotted, and could in fact be smaller and less energetic than it seems. What we need are more observations over the next few weeks.

“It’s early days, so I think the prudent approach is to moderate our expectations and then be ‘pleasantly surprised’ later,” astronomer Karl Battams (U.S. Naval Research Laboratory) told Universe Today. “That said, there’s clearly the potential for this to be a very exciting comet. The best analog we have is comet Lovejoy in 2011, which was discovered just a couple of weeks from perihelion, versus this one which is nearly a month away.”

The comet reaches perihelion on October 28^th, 0.0082 AU from the Sun. That’s 762,600 miles from solar center, just 330,600 miles from the surface of the Sun. The solar radius is about 432,000 miles. As always seems to be the case, southern hemisphere observers will get a better view of the comet leading up to perihelion in mid-October as it approaches the Sun through the constellation Hydra. The comet will be visible low to the east at dawn, and ‘could’ break +6^th magnitude in the final week of October. The comet passes 0.306 AU from the Earth on October 23^rd after which, things could start to get interesting.

Prospects for Sungrazer A1 ATLAS

As of writing this, best estimates for peak magnitudes for comet S1 ATLAS top out at -7—think a bright daytime comet, but very close to the Sun—though -1^st magnitude or so is probably more conservative.

Northern hemisphere viewers might get best views of the comet low to the east at dawn after perihelion… if it survives.

“This Kreutz-group comet won’t pass quite as close to the Sun as W3 Lovejoy, so it’s not unreasonable to guess that it will aid its survival potential.” Says Battams. “Assuming so, it might be briefly visible to northern hemisphere observers very low in the early morning (in) southeast skies after perihelion, but it would require good viewing circumstances (a clear, low horizon)… and won’t hang around there for long.”

The comet enters the Solar Heliospheric Observatory (SOHO’s) LASCO C2/C3 field of view on October 26^th, and exits on the 29^th. It’s strange to think: prior to SOHO’s launch in 1995, astronomers knew of less than a handful of sungrazer comets. Now, thanks to the mission, we know of 5,065 sungrazing comets and counting.

Classic Sungrazers of Yore

2011’s sungrazer W3 Lovejoy survived a passage just 87,000 miles from the surface of the Sun… Comet ISON, however, did not survive a 0.001244 AU, 116,000 mile surface pass at perihelion on U.S. Thanksgiving Day 2013.

Long-time comet watchers will remember sungrazer Ikeya-Seki, which survived a 280,000 mile pass (just a little over the Earth-Moon distance) from the surface of the Sun. That comet went on to dazzle observers in 1965.

“What I will say is that I am very excited at the ‘prospect,’ and will be watching the evolution of this extremely closely over the next couple of weeks.” says Battams. “I think by mid-October we’ll be able to state some facts with a lot more certainty.”

It seems like good comets always come in pairs…remember Hale-Bopp and Hyakutake in the late 90s? We (finally) caught sight of comet C/2023 A3 Tsuchinshan-ATLAS this morning from here in Bristol, Tennessee, looking like a fuzzy ‘star’ with a short tail in the brightening twilight low to the east, peeking out between pine trees.

We’re cautious for now when it comes to S1 ATLAS. But remember: comets never read predictions… and S1 ATLAS could well surprise us.