If you’ve heard about comet Tsuchinshan-ATLAS (also called C/2023 A3 and Comet A3) you’ll want to find it in the night sky tonight and every night this week — so here’s how.
The first rule of comet-hunting is this — it’s best to go see it as soon as you can, 45 minutes after sunset where you are. You need clear weather to the west, so if you have it, use it. If you find it, here’s how to photograph it.
How long will the comet be visible? “It should start to become clearly visible around the evening of the Oct. 12, and be very prominent on Oct. 13 and Oct. 14 when it will have a bright downward spike in addition to its normal upward pointing tail,” said astronomer Dr. Qicheng Zhang of Lowell Observatory in Flagstaff, Arizona, who has been monitoring the comet, in an email last week. “It should stay fairly prominent over the next few days as the fading comet is balanced out by the darker sky as it moves away from the sun until about Oct. 19 and Oct. 20.”
All you need to see the comet is your naked eyes, but any pair of binoculars will give you an incredible view. Here’s exactly where and when to see the comet every day this week and beyond:
Where And When To See The Comet On Monday, Oct. 14
Need to know: the first of two of the best nights to see the comet at its brightest and best as the comet spends its last day in the constellation Virgo. It will display a new rare “anti-tail” as Earth passes through the comet’s orbital plane
This evening, the comet will due west, 25 degrees from the sun in Virgo, and visible close to the western horizon about 45 minutes after sunset. It will set about an hour and 20 minutes later. That means it will be in the sky for about 20 minutes longer than on Sunday. The waxing gibbous moon will be bright, 91%-lit, which will make the night sky less than dark. Find the bright planet Venus and the bright star Arcturus; the comet will be almost exactly halfway along an imaginary line drawn between them.
Note: The Virtual Telescope will be live-streaming the comet — and its new “anti-tail” — from 17:00 UTC (1:00 p.m. EDT) on Oct. 14.
Where And When To See The Comet On Tuesday, Oct. 15
Need to know: the second of two of the best nights to see the comet at its brightest and best as the comet moves into the constellation Serpens. Those with telescope can see two deep-sky objects close to it — globular cluster M5 and another (faint) comet called 13P/Olbers.
This evening, the comet will due west, 30 degrees from the sun in Serpens, and visible close to the western horizon about 45 minutes after sunset. It will set about an hour and 20 minutes later. That means it will be in the sky for about 40 minutes longer than on Sunday. The waxing gibbous moon will be 97%-illuminated, which will make the night sky less than dark. Find Venus and Arcturus; the comet will be just above halfway along an imaginary line drawn between them.
Note: The Virtual Telescope will be live-streaming the comet — and views of M5 and 13P/Olbers — from 17:00 UTC (1:00 p.m. EDT) on Oct. 14.
Where And When To See The Comet On Wednesday, Oct. 16
Need to know: the near-full “Hunter’s Moon” will shine in the east and you gaze west.
This evening, the comet will due west, 33 degrees from the sun in Serpens, and visible close to the western horizon about 45 minutes after sunset, setting around two hours later. That’s means it will be in the sky for about 15 minutes longer than on Tuesday. The comet will once again be above a point roughly halfway between Venus and Arcturus, only higher.
Where And When To See The Comet On Thursday, Oct. 17
Need to know: the full “Hunter’s Moon” will rise in the east shortly after sunset from North America (and slightly before from Europe) — so be outside at sunset/moonrise where you are.
This evening, the comet will due west, 37 degrees from the sun in Serpens, and visible close to the western horizon about 45 minutes after sunset, setting around two hours 10 minutes later. That’s means it will be in the sky for about 15 minutes longer than on Wednesday. The comet will once again be above a point roughly halfway between Venus and Arcturus, only higher.
Note: The Virtual Telescope will be live-streaming the comet and vies of the full “Hunter’s Supermoon” from 17:00 UTC (1:00 p.m. EDT) on Oct. 14.
Where And When To See The Comet On Friday, Oct. 18
Need to know: now just past full, the “Hunter’s Moon” will rise about 50 minutes after sunset/moonrise where you are, which is about the same time as the comet becomes visible.
This evening, the comet will due west, 40 degrees from the sun in Serpens, and visible close to the western horizon about 45 minutes after sunset, setting around two hours 25 minutes later. That means it will be in the sky for about 15 minutes longer than on Thursday. The comet will be above a point roughly halfway between Venus and Antares, making a triangle shape. A 96.4%-illuminated waning gibbous moon will rise while you look for the comet.
Where And When To See The Comet On Saturday, Oct. 19
Need to know: the comet has been visible to the naked eye until now, but around Saturday, Oct. 19 or Sunday, Oct. 20, it will fade quickly as it enters the constellation Ophiuchus. Use binoculars!
This evening, the comet will due west, 42 degrees from the sun in Ophiuchus, and visible close to the western horizon about 45 minutes after sunset, setting around two hours 35 minutes later. That means it will be in the sky for about 10 minutes longer than on Friday. The comet will be above a point roughly halfway between Venus and Antares, making a vast triangle shape.
Where And When To See The Comet On Sunday, Oct. 20
Need to know: the comet has been visible to the naked eye until now, but around Saturday, Oct. 19 or Sunday, Oct. 20, it will fade quickly. Use binoculars!
This evening, the comet will due west, 45 degrees from the sun in Ophiuchus, and visible close to the western horizon about 45 minutes after sunset, setting around two hours 45 minutes later. That means it will be in the sky for about 10 minutes longer than on Saturday. Now visible in astronomical darkness, the comet will again be above a point roughly halfway between Venus and Antares, making a vast triangle shape.
Where And When To See The Comet On Monday, Oct. 21
Need to know: the comet — now not visible to the naked-eye — will nevertheless be a pretty sight with binoculars during astronomical darkness.
This evening, the comet will due west, 47 degrees from the sun in Ophiuchus, and visible close to 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. Find bright Venus and the bright star Arcturus; the comet will be high above them as the third point of a vast triangle.
Where And When To See The Comet In Late October And November
According to Sky & Telescope, you won’t see it with the naked eye on Halloween — Oct. 31 — though it will probably remain visible through binoculars until early November.
After it’s disappeared from view, it will gradually travel back to the outer solar system and the Oort Cloud. Its orbit may only be weakly gravitationally bound to the sun, so it will likely never return to loop around the sun.
What Is A Comet?
A comet is a cosmic snowball. Comprised of gas, dust and ice, they’re typically from the Oort Cloud, a sphere of debris around the solar system — the leftovers of its creation — that’s home to millions of comets. The sun’s gravitational pull acts on these comets, bringing them on long journeys to the inner solar system, where the sun’s radiation slightly heats them, causing them to release gas and dust into space as a tail.
Comet Tsuchinshan-ATLAS appears to be in an orbit of the sun that takes 80,000 years to complete, making it a long-period comet. It’s traveling at around 180,000 miles per hour (290,000 km per hour).
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.
