Comet C/2023 A3 Tsuchinshan–ATLAS will soon fly past Earth

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A recently discovered comet, known as C/2023 A3 Tsuchinshan–ATLAS, will make its closest approach to Earth on Saturday. Sky watchers should not miss this event as it may be the last time the comet will be seen in the night sky for 80,000 years.

The comet successfully reached perihelion, its closest point to the Sun in its orbit around the parent star, on September 27 and was visible to people in the Southern Hemisphere throughout September and early October. Now the icy body is on its way out of the inner solar system and will be visible to people in the Northern Hemisphere from mid-October to early November, according to NASA.

On Saturday, the comet will come within about 44 million miles (nearly 71 million kilometers) of Earth. According to NASA, the comet is making its first documented flyby of our planet. With its 80,000-year orbit, the celestial body was probably last seen from Earth during the time of the Neanderthals.

According to EarthSky, if you want to catch a glimpse of the once-in-a-lifetime event, you should look into the western part of the night sky shortly after sunset.

The comet will look like a bright fireball with a long, outstretched tail in the dark sky. Bill Cooke, head of NASA's Meteoroid Environment Office at the Marshall Space Flight Center in Huntsville, Alabama, recommends binoculars for better viewing of the comet.

“It won’t fly across the sky like a meteor. It just seems to hang there and will slowly change position from night to night,” Cooke said. “If you can see (the comet) with the naked eye, the binoculars will blow you away.”

Tsuchinshan–ATLAS was discovered separately in 2023 by observers from China's Tsuchinshan Observatory and an Asteroid Terrestrial-Impact Last Alert System (ATLAS) telescope in South Africa, hence the comet's namesake, according to NASA.

The celestial object comes from the Oort Cloud, “a largely spherical collection of comets barely bound to our solar system, thousands of times (further) from the Sun than we are,” said astronomer Dr. Teddy Kareta, a postdoctoral researcher at Lowell Observatory in Flagstaff, Arizona, in an email.

Scientists weren't sure whether the comet, made of ice, frozen gases and rocks, would survive its journey around our solar system's parent star. But the comet appears to be largely intact and “made it through with flying colors,” Cooke said.

Because of its proximity to the Sun, Tsuchinshan-ATLAS will experience an effect known as forward scattering, which will cause the comet to appear brightest around Wednesday as sunlight reflects off its gas and debris. However, because the comet is blocked by the Sun's strong glare, it is unlikely that the celestial body will become visible in the sky until a few days later, Cooke added.

If all goes well, Tsuchinshan-ATLAS will return to this point in its orbit in about 80,000 years, but comets can be unpredictable – it's possible that another planet's gravity could change the comet's course, Cooke added.

For those who cannot see Tsuchinshan ATLAS in the night sky, the Virtual Telescope Project in Italy will offer a live broadcast of the comet at its brightest point on Wednesday and at its greatest distance on Saturday to earth.

“For many people, especially children, the sight of a bright comet in the night sky is a beautiful and life-changing experience,” Kareta said.

“Even though a comet every few years is barely bright enough to be seen with the naked eye, comets that have the potential to be highly visible to many are rare.” If you can try to see it, you should do it – and you should take everyone you can with you so they can experience it too.”

The next full moon, which peaks on October 17, could affect comet viewing as its illumination affects the visibility of other objects in the night sky. Dubbed the “Hunter's Moon,” it will be a supermoon and will be the closest of the year at 222,095 miles (357,428 kilometers) from Earth.

But there are other ways to observe celestial bodies, as a second comet, known as Comet C/2024 S1 (ATLAS), could appear in the night sky in late October, according to EarthSky.

In the meantime, sky watchers can expect a busy meteor shower season as 2024 comes to a close. According to the American Meteor Society, here are the peak dates for upcoming celestial activity:

Orionids: 20-21 October

Southern Taurids: 4th-5th November

Northern Taurids: 11th-12th November

Leonids: 17th-18th November

Geminids: 13th-14th December

Ursids: 21st-22nd December