Look up, stargazers: A comet discovered last year is getting brighter as it makes its closest pass by Earth later this week, and this could be humanity’s last chance to see the comet before it disappears into the cosmic depths.
The celestial visitor is Comet Tsuchinshan-ATLAS, or C/2023 A3 to scientists. Astronomers are expecting the comet to be especially vivid, possibly rivaling the brightness of Jupiter in the night sky. The comet is expected to be at its brightest on Wednesday and potentially visible through the end of the month.
“This one is, I would say, a once-in-a-lifetime opportunity,” said Gianluca Masi, an astrophysicist based in Italy and the scientific director of the Virtual Telescope Project. “This comet is for everyone.”
What is Comet Tsuchinshan-ATLAS?
Tsuchinshan-ATLAS, like all comets, is a frozen chunk of leftover material from the birth of the solar system. The comet begins to melt as it nears the sun, causing the ball of ice to sprout a diffuse tail.
The comet was first detected by astronomers at the Tsuchinshan Observatory, known also as Purple Mountain Observatory, in China on Jan. 9, 2023. A month later, the comet was independently spotted by observers using the Asteroid Terrestrial-Impact Last Alert System, or ATLAS, telescope in South Africa.
Hence, its name, Tsuchinshan-ATLAS. The comet comes from the Oort Cloud, a realm filled with frozen debris on the outer edge of our solar system. Initial observations suggest that the comet may orbit the sun once every 80,000 years.
Such an orbit takes Tsuchinshan-ATLAS far “out of the realm of the planets,” said Michelle Nichols, the director of public observing at the Adler Planetarium in Chicago. By contrast, Neptune’s orbit around the sun takes about 165 years, while Pluto travels around the sun about once every 248 years.
But this comet may actually never come back around again. As it travels away from the sun again, the effects of other objects’ gravity could kick the comet out of the solar system altogether, Ms. Nichols said.
Comet Tsuchinshan-ATLAS disappeared for some time earlier this year but was seen once again last month in southern skies, and has since been steadily wandering into view in the Northern Hemisphere.
How bright will Comet Tsuchinshan-ATLAS get?
With limited data, astronomers sometimes struggle to discern just how bright a comet will get.
“Comets behave like cats,” Dr. Masi said. “They have a tail, and they do exactly what they want.”
But predictions of this comet’s orbit and brightness have so far been pretty accurate, he added.
Tsuchinchan-ATLAS will make its closest approach of Earth on Oct. 12, within a distance of 44 million miles. But the comet is expected to be brightest on the evening of Oct. 9 — because it will be in just the right position for dusty debris to scatter light from the sun directly toward viewers on Earth, temporarily boosting the comet’s brilliance.
This effect is known to astronomers as forward scattering. And if it is intense enough, experienced observers might even be able to see the comet during the day, Ms. Nichols said.
But that’s a big if, she said, adding that she does not recommend people look for the comet until the sun goes down.
What is the best way to see Comet Tsuchinshan-ATLAS?
Ms. Nichols thinks this comet is worth making the effort to observe, if you’re able.
“Any comet that even remotely approaches naked-eye visibility is a comet worth going out to see,” she said. “Because we just don’t get them all that often.”
Astute observers may have already caught the comet in morning skies, but it should be visible in the evening with the naked eye from Oct. 9 through the end of the month.
To see the comet on Oct. 9, Dr. Masi recommends going to the darkest location you can find with an unobstructed view of the western horizon. A few minutes after the sun goes down, search low in the sky around where it has set. The comet, which will look fuzzier than nearby stars, might be difficult to spot in the waning light of sunset. Binoculars or a small telescope can enhance the view.
After Oct. 9, Tsuchinshan-ATLAS will remain visible and may even be easier to see because it will appear higher in the sky. But the comet will also be dimmer. Light from the moon may affect observing, too, particularly during the supermoon of Oct. 17.
Skywatching events for the comet may be organized through your local planetarium or astronomy club. The Virtual Telescope Project is also hosting a live broadcast on Oct. 9.
Are any other comets coming up?
Humanity has been lucky with comets during the past few years. There was the devil-horned Pons-Brooks, prominent for months before disappearing last spring, as well as Comet NEOWISE, among the brightest in decades, in 2021. Before that, the last snowball to make such a splash was Hale-Bopp in 1997.
Our astronomical fortune continues: Another bright comet, discovered at the end of September, could blaze through our night skies later this month. It’s called C/2024 S1, and it may be brightest around Oct. 28.
A double feature would be especially rare. “To my memory, I cannot remember a similar case of two amazing comets back-to-back,” Dr. Masi said. Despite running a virtual observing program, he still recommends people go out to see such sights in real life.
“Find the best place to enjoy this cosmic gift,” he said. “You will really see how beautiful the universe is.”
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