SALT LAKE CITY — The universe is serving up an encore celestial number to Friday’s geomagnetic storm that made the northern lights visible as far south as southern Utah. This week, as a comet hurtles through the inner solar system, stargazers may be able to spot it with their unaided eye.
Beginning Saturday and lasting for about 10 days, Comet 2023 Tsuchinshan-ATLAS — C/2023 A3 for short — is expected to appear in the evening sky. If predictions hold, skygazers will be able to see it low on the western horizon on Saturday or Sunday. As it slingshots away from the sun into the netherworld of the outer solar system, you may see it rise higher in the sky each night until about Oct. 21, brightening before finally fading away.
Besides the potential to be able to see C/2023 A3 with your naked eye, it may also be possible to see its long tail with your naked eye. University of Utah astronomer Paul Ricketts said it looks like the comet is sporting about a 10-degree-long tail. The comet is at magnitude 2, which is bright enough to see not long after sunset.
However, comets are notoriously unpredictable, and Patrick Wiggins, NASA/JPL solar system ambassador to Utah, used a cat analogy to express his conservative predictions.
“Comets and cats both have tails,” said Wiggins, “and they both do what they want.”
Local amateur astronomer Kurt Fisher also has high hopes for the comet and has been following it closely. C/2023 A3 has survived its trip around the sun, so it hasn’t broken up, said Fisher. The biggest variable now will be its brightness.
The comet’s path around the sun is offset from our orbit, which is why it was visible in the Southern Hemisphere first. As it crosses the ecliptic and appears in our evening sky, the comet’s position, which determines how bright the comet’s tail gets, is unknown. This angle was favorable for viewers in the Southern Hemisphere, but how our luck pans out in the Northern Hemisphere is still a guess.
Comets and cats both have tails, and they both do what they want.
–Patrick Wiggins, NASA/JPL solar system ambassador to Utah
Ricketts said what we know about the comet can only be gleaned by pictures and data coming from those who have seen it. Wiggins is hesitant to tell people what to expect until he sees it himself, which he plans to try this weekend at the Salt Lake Astronomical Society star party at the Stansbury Park Observatory.
Still, the comet has potential. As of Friday evening, the coma, or nucleus of the comet, is about as bright as the stars in the constellation Cassiopeia, which appears in the north shortly after sunset. With C/2023 A3 close to the horizon at first, it will be hard to spot. However, as the comet rises in the night sky, it will be visible for longer and will be brighter, said Ricketts. The comet will then fade to fainter magnitudes as it climbs higher until it is no longer visible.
Again, brightness is all dependent on conditions, all three astronomers said.
Ricketts suggested finding an accurate map online to aid your observation. When the comet is low on the horizon, it may be necessary to look for it through binoculars, making it harder to find. It is also important your vantage point is clear of mountains: Antelope Island or the West Desert for northern Utahns and Cedar Breaks for those in the south are good suggestions, he said.
If you look for the comet right after sunset, especially with binoculars or a telescope, take care to avoid looking into the sun, Fisher warned.
Fisher says the tail will be about as long as the amount of sky covered by your spread fingers at arm’s length. Ricketts said the tail will likely be fainter than the comet, but still visible. You will get great results if you point a camera with medium zoom at the apparition, he said.
The final ingredients to a successful comet hunt are dark skies and good weather. Haze or clouds on the horizon will obscure the comet, and dark skies will help when the target is both low and high in the sky, said Ricketts.
Fisher said he gets excited for these more ephemeral astronomical events, such as comet sightings and auroras.
Ricketts gets excited to be “the only person in the next 80,000 years” to see sights like this.
“Well, besides everyone else who sees it, too,” he said.
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