Comet Tsuchinshan-ATLAS is now past it best, having transited from being a bright, naked-eye object in the post-sunset sky to a deep-sky object that’s visible into true darkness.
Can you see comet Tsuchinshan-ATLAS (also called C/2023 A3 and Comet A3) with the naked eye tonight? Probably not. It’s not as bright as it was, so you’ll need binoculars and patience to see it, particularly from urban areas with light-polluted skies. But you may be able to photograph it.
“Around Oct. 20, a window of true darkness begins to open up between twilight and moonrise if you’re far from the skyglow of city lights,” states Sky & Telescope. “But by then, the comet, now high in the sky, will have started to fade and shrink. It will diminish into the distance in the following days, becoming invisible to the unaided eye later in the month even under ideal, dark-sky conditions.”
Tonight, Monday, Oct. 21, you should find a dark location using a light pollution map or visit a Dark Sky Place — and for two reasons. As well as the comet being a bright object in a pair of binoculars, the Orionid meteor shower peaks.
The best time to see shooting stars is after midnight — in the early hours of Tuesday, Oct. 22 — though anytime after dark is good. That said, the source constellation, Orion, will rise around midnight in the southeast. You may see around 20 shooting stars per hour.
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: Monday, Oct. 21
Position: west, 47 degrees from the sun in Ophiuchus
Time: 45 minutes after sunset where you are
Magnitude: +2.2
Comet’s distance from the sun: 68 million miles (109.5 million kilometers)
Comet’s distance from Earth: 59.7 million miles (96 million kilometers)
This evening, the comet will be visible high above the western horizon about 45 minutes after sunset, setting just under three hours later. That means it will be in the sky for about 10 minutes longer than on Sunday.
That means the comet will be high in the sky and remain so as twilight turns to astronomical darkness. Find bright Venus and the bright star Arcturus; the comet will be high above them as the third point of a vast triangle. Scan with a pair of binoculars until you find it.
Why Does Comet Tsuchinshan-ATLAS Have A Curved Tail?
The tail of a comet is typically slightly curved because of the Coriolis effect, which affects large-scale weather patterns, but can be seen in everyday events, such as making the water jets coming off a rotating sprinkler look curved. “The comet is going around the sun, so as it does that, the direction the sunlight pushes on the dust spins around just like the sprinkler nozzle direction,” said astronomer Dr. Qicheng Zhang of Lowell Observatory in Flagstaff, Arizona, who has been monitoring the comet, in an email.
“We’re actually viewing this comet’s curved tail edge on, so it will look like part of the tail is above the head of the comet, but then the tail wraps down past the head of the comet, making it look like another part of the tail is below the head of the comet, like it has two tails pointing in opposite directions,” said Zhang.
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.
