Where is Comet Tsuchinshan-ATLAS tonight, Wednesday, Oct. 16? The icy visitor from the outer solar system, which orbits the sun once in every 80,000 years, is now visible in the western sky after sunset — and it’s now reasonably high and easy to see, clear skies allowing.
Get out just after sunset and you’ll also see the near-full “Hunter’s Moon” shining brightly behind you in the east and you gaze west.
Wednesday, Oct. 16, is the ideal time to look for the comet (also called C/2023 A3 and Comet A3) from the northern hemisphere. It reached its perihelion — the closest it gets to the sun — on Sept. 27 and on Saturday was at its closest to Earth, passing about 44 million miles (71 million kilometers) distant.
It’s now 48 million miles distant, but crucially, it’s higher in the sky, so easier to see above mountains and buildings. If you find it, here’s how to photograph it.
Here’s exactly when and where you need to look to see the comet with your naked eyes on Wednesday, Oct. 16.
Note: times and viewing instructions are for observers at mid-latitudes in the Northern Hemisphere. Check the exact time of sunset where you are and the comet’s setting times on Stellarium Web for times accurate for your exact location.
How To Locate Comet Tsuchinshan-ATLAS: Wednesday, Oct. 16
Position: west, 33 degrees from the sun in Serpens
Time: 45 minutes after sunset where you are
Magnitude: +1.1
Comet’s distance from the sun: 57.8 million miles (93.1 million kilometers)
Comet’s distance from Earth: 48 million miles (77.2 million kilometers)
Wednesday, Oct. 16, is a great time to get a good view of the comet as it gains height in the post-sunset sky. That’s despite the waxing gibbous moon now being 99.7%-lit in the southeastern sky on its way to being a full “Hunter’s Moon” on Thursday, Oct. 17.
This evening, the comet will be visible above the western horizon about 45 minutes after sunset, setting around two hours later. That means it will be in the sky for about 15 minutes longer than on Tuesday.
If you have a completely clear horizon, find the bright planet Venus and the bright twinkling (and reddish) star Arcturus, the brightest star in the constellation Boötes; the comet will be just above a point roughly halfway between them.
All you’ll need to see the comet is your naked eyes, but a pair of binoculars will give you a great view.
Why Is Is Comet Tsuchinshan-ATLAS So Bright?
There are dozens of comets in the inner solar system at any one time. Few of them, however, become visible to the naked eye — or even become a binocular object. So what’s so special about comet Tsuchinshan-ATLAS?
“The comet is passing between the Sun and the Earth right now, so light diffracted (bent around) by dust grains in the tail, which is normally concentrated in the direction opposite the sun from the comet, is now being concentrated in the direction of Earth,” said astronomer Dr. Qicheng Zhang of Lowell Observatory in Flagstaff, Arizona, who has been monitoring the comet, in an email. “This is the same effect that makes thin clouds really bright when backlit by the sun; only in that case, it’s ice crystals or water droplets doing the light bending.”
As a bonus, the tail of a comet typically points away from the sun, which means it’s pointing right toward Earth, putting us close to the tail and making it look bigger in the sky, explained Zhang.
“A third factor is the comet passed its closest point to the sun last month, which is roughly the point where it released dust at the highest rate,” said Zhang. “Dust, however, doesn’t just disappear after it’s released from a comet — it goes into making the tail bright.”
Since it’s passing between Earth and the sun after, rather than before, the comet has released most of its dust, the tail will be extra bright.
Check my feed every day this week and next for a daily “comet tracker” with sky-charts and tips for viewing the comet.
Wishing you clear skies and wide eyes.
