How to spot Comet Tsuchinshan-Atlas

What is Comet Tsuchinshan-Atlas?

Comet Tsuchinshan-Atlas is a bright comet that’s about to fly around the Sun and pass near Earth. It’s possible to see the comet in the pre-dawn sky right now, and in a couple of weeks, when the comet makes its closest approach to Earth, it may offer an even more impressive sight. Only time will tell for sure.

Officially known as C/2023 A3, Comet Tsuchinshan-Atlas gets its longer name from the facilities that first spotted it back in 2023: the Purple Mountain Observatory of the Chinese Academy of Sciences (or Tsuchinshan Chinese Observatory) and the Asteroid Terrestrial-impact Last Alert System (ATLAS). Since its initial discovery, amateur astronomers and scientists around the world have made thousands more observations of this comet. Many are tracking Tsuchinshan-Atlas in hopes that it will become extremely bright — so bright that it outshines the stars, Jupiter, and even Venus.

Already, Comet Tsuchinshan-Atlas has gotten about one million times brighter over the past couple years as it has traveled closer to the Sun. Yet it’s also notoriously hard to predict exactly what comets will look like in advance.

Optimists describe Comet Tsuchinshan-Atlas as “the comet of the century.” They say it will outshine everything but the Moon in the night sky and that it will stretch its tail over a huge portion of the sky. In that case, people around the world would be able to see the comet without trying at all. On the other hand, some people, like astronomer Dr. Zdeněk Sekanina, have predicted that the comet will break apart around the closest point in its orbit to the Sun, or “perihelion.” Comet Tsuchinshan-Atlas shows no clear signs of fragmenting right now, but that could always change. 

There are also plenty of comet forecasts that fall somewhere in between. For instance, Tsuchinshan-Atlas could end up brighter than Venus and easy to find for anyone who knows to look, but still not quite bright enough to be obvious for a newbie stargazer. You can track how bright Tsuchinshan-Atlas is by checking the IAU Minor Planet Center or the Comet OBServation database (COBS). Keep in mind that the comet may seem brighter on paper than it really looks in the sky because, unlike a star, a comet’s light can be spread over a broad area.

When to see Comet Tsuchinshan-Atlas

There are likely two best times to see Comet Tsuchinshan-Atlas: tomorrow, Sept. 27, when the comet passes closest to the Sun, and mid-October, when the comet hopefully reappears near Earth brighter than ever.

During late September and the first few days of October, you can find Comet Tsuchinshan-Atlas in the constellation Sextans. Look to the east, where the comet will rise about an hour before the Sun if you’re in the Northern Hemisphere. If you’re in a Southern Hemisphere, the comet will rise a bit earlier and be easier to see.

For most of early October, Tsuchinshan-Atlas will be too close to the Sun to be easily visible. Then, starting around Oct. 10 — if all goes well — the comet should be visible after sunset near the horizon in the west. With every passing day, Tsuchinshan-Atlas will start the evening higher in the sky and be easier to spot, unless it gets too dim.

Where can I watch Comet Tsuchinshan-Atlas?

Comet Tsuchinshan-Atlas is currently visible from both the Northern and Southern Hemispheres at night, though it’s a bit easier to spot the farther south you are. When the comet reappears in mid-October, the situation will flip, and observers farther north will be better positioned to see the comet. Someone in Australia or South Africa, for example, might expect to have a harder time finding Comet Tsuchinshan-Atlas than someone in India or Central America. 

You will likely need binoculars to see Comet Tsuchinshan-Atlas, and a telescope with a wide field of view might be even better. Be sure to go somewhere with a good view out to the horizon, since the comet will not appear very high up in the sky. And if you live somewhere with intense light pollution, like the heart of a major city, you will probably have to travel to a darker location farther from lights. 

How to see Comet Tsuchinshan-Atlas

In late September, look to the constellation Sextans, above the eastern horizon, about an hour before the Sun rises in the morning sky. Use binoculars or a telescope to spot the comet — right now, Tsuchinshan-Atlas is dim enough that it would be a challenge to see with the naked eye. It’s probably also not possible to see the comet from the heart of a major city, so try to head somewhere with a little less light pollution. 

Things could be different in mid-October. As the comet makes its closest approach to Earth, look to the constellations Leo, then Virgo, above the western horizon shortly after sunset. By then, the comet’s brightness might have changed enough that it could be visible even in the heart of a major city. No matter what, though, stargazing from a darker location will give you the best views.

Try to go somewhere with a good view out to the horizon, since the comet will not appear very high up in the sky. Let your eyes adjust to the dark for several minutes. If you’re using both eyes, look slightly above the comet instead of keeping it in the center of your vision. This “averted vision” technique will help you make out details better in the dark.

What is a comet?

Comets are small, irregularly shaped worlds of rock and ice that survived the formation of the Solar System — or that were born out of collisions between other Solar System bodies — and that now orbit the Sun. Comets are similar to asteroids, but more icy because they formed farther from the Sun and continue to spend most of their time there. When they do come closer to the Sun, comets warm up and throw off gas and dust, giving them tails.

It’s possible that Comet Tsuchinshan-Atlas came from the Oort Cloud, a huge collection of icy bodies that orbit the Sun far beyond any of the planets. Tsuchinshan-Atlas may return to the far outer Solar System on a long orbit spanning tens of thousands of years — or, it may pass by the Sun only once before being thrown out of the Solar System entirely. As it stands, scientists aren’t completely sure.