A rare and extraordinary astronomical event is set to occur this Saturday, as comet C/2023 A3 Tsuchinshan–ATLAS makes its closest approach to Earth. Sky-watchers won’t want to miss this unique opportunity, as it might be the last time to see the comet for the next 80,000 years. This celestial spectacle, which has captivated astronomers since its discovery, promises to be a sight to remember.
The comet reached its perihelion, the point in its orbit closest to the Sun, on September 27. It was visible in the Southern Hemisphere throughout late September and early October. Now, as it begins its journey away from the Sun, it will be visible to those in the Northern Hemisphere, particularly from mid-October to early November, according to NASA.
On October 14, Tsuchinshan–ATLAS will come within approximately 44 million miles (71 million kilometers) of Earth. This marks the comet’s first documented visit to our planet, according to NASA scientists. With an orbit of around 80,000 years, the last time this comet was seen from Earth was during the era of the Neanderthals.
For those eager to witness the comet, experts recommend looking toward the western sky shortly after sunset. As it moves across the sky, Tsuchinshan–ATLAS is expected to appear as a bright fireball with a long, glowing tail. Bill Cooke, head of NASA’s Meteoroid Environment Office at the Marshall Space Flight Center, advises using binoculars for a better view. “It’s not going to zing across the sky like a meteor. It will just appear to hang there, and it will slowly change position from night to night,” Cooke said. He added that viewing it through binoculars would be a particularly stunning experience: “If you can see [the comet] with your unaided eye, [using] the binoculars will knock your socks off.”
Discovery and Origins of Comet Tsuchinshan–ATLAS
Comet C/2023 A3 Tsuchinshan–ATLAS was discovered independently in 2023 by astronomers at China’s Tsuchinshan Observatory and by a telescope that is part of the Asteroid Terrestrial-impact Last Alert System (ATLAS) located in South Africa. This dual discovery led to the comet’s distinctive name. NASA noted that this comet comes from the Oort Cloud, a distant, spherical region of icy bodies that surrounds our solar system. The Oort Cloud is located thousands of times farther away from the Sun than Earth is, making it a source of long-period comets like Tsuchinshan–ATLAS.
Tsuchinshan–ATLAS, composed of ice, frozen gases, and rock, had a perilous journey as it passed near the Sun. Some scientists were unsure whether the comet would survive the intense heat and radiation of its close encounter with the Sun. However, it appears that Tsuchinshan–ATLAS has remained largely intact. Cooke commented on the comet’s survival, saying it “made it with flying colors.”
As Tsuchinshan–ATLAS moves further away from the Sun, it will experience a phenomenon known as forward scattering, where sunlight reflects off the gas and debris surrounding the comet. This will cause the comet to shine at its brightest around mid-October, although the Sun’s glare may make it difficult to observe for a few days, according to Cooke. He also noted that while the comet is expected to return in 80,000 years, comets are unpredictable, and gravitational forces from other planets could alter its course.
For those unable to view the comet in person, the Virtual Telescope Project in Italy will offer live streams of the comet on both October 11, when it is at its brightest, and October 14, when it is closest to Earth.
Astronomer Dr. Teddy Kareta, a postdoctoral associate at Lowell Observatory, emphasized the significance of such events. “For many people, and especially children, seeing a bright comet in the night sky is a beautiful and life-changing experience,” Kareta said. He added that while there are comets visible every few years, “comets that have the potential to be easily visible to many are rare.” Kareta encouraged everyone to try to witness the event and to share the experience with others: “If you can try to see it, you should — and you should take whoever you can with you so they can experience it too.”
Additional Celestial Events to Look Forward To
While the comet is the highlight of October’s astronomical calendar, it’s not the only celestial body that sky-watchers should keep an eye on. A full moon, known as the hunter’s moon, is set to peak on October 17. This supermoon will be the closest of the year, appearing just 222,095 miles (357,428 kilometers) from Earth. However, its brightness may interfere with the visibility of the comet and other objects in the night sky.
In addition to Tsuchinshan–ATLAS, another comet may grace the skies later this month. Comet C/2024 S1 (ATLAS) is expected to make its debut in late October, providing another opportunity for sky-watchers to spot a rare celestial object, according to EarthSky.
As the year draws to a close, sky-gazers can look forward to several prominent meteor showers. These include the Orionids, peaking from October 20 to 21, the Southern Taurids from November 4 to 5, and the Northern Taurids from November 11 to 12. The Leonids meteor shower will be visible from November 17 to 18, while the Geminids, one of the brightest meteor showers of the year, will peak from December 13 to 14. The Ursids meteor shower, which peaks from December 21 to 22, will close out 2024’s impressive array of celestial events.
This month, with its abundance of meteor showers, supermoons, and comets, offers multiple opportunities to marvel at the wonders of the universe. Tsuchinshan–ATLAS, however, remains the highlight, as this once-in-a-lifetime event will not occur again for 80,000 years. Sky enthusiasts are encouraged to make the most of this rare opportunity to witness the ancient comet’s journey across the night sky.
In the words of Bill Cooke, “If all goes well, Tsuchinshan–ATLAS will return at this point in its orbit in around 80,000 years, but comets can be unpredictable — it’s possible that another planet’s gravity could change the comet’s course.”