In recent months, excitement has been gradually building over the approach of a new comet named Tsuchinshan-ATLAS, officially catalogued as C/2023 A3.
Comet Tsuchinchan-ATLAS (C/2023 A3) was first discovered at the Purple Mountain Observatory’s XuYi Station in China on January 9, 2023, then lost, and was discovered for the second time 44 days later at the Asteroid Terrestrial Impact Last Alert System (ATLAS) search project station in Sutherland, South Africa. There is hope Rise high that it would develop into a bright object visible to the naked eye by the fall of 2024.
But a new technical document A well-known comet expert recently published a report on July 9 stating that Comet Tsuchinshan-ATLAS is unlikely to dazzle, but will break up and disintegrate before it has a chance to orbit the Sun in late September.
The report comes from Dr. Zdeněk Sekanina, formerly of NASA/JPL, and an expert on split and dissolving comets. In his report, Dr. Sekanina gives three main reasons why he believes the comet is nearly complete:
“The purpose of this paper,” writes Dr. Sekanina, “is not to disappoint comet observers who were looking forward to a new naked-eye object in October, but to present scientific arguments that do not seem to support such expectations.” While openly admitting that predicting the disintegration of a comet before its closest approach to the Sun (perihelion) is “admittedly a very risky undertaking,” Dr. Sekinina believes that “the time has come to proceed with it.”
Comet Tsuchinshan-ATLAS is expected to reach perihelion on September 27, at a distance of 58 million kilometers from the Sun. This distance is equal to the average distance of Mercury, the closest planet to our star.
If you’re hoping to see Comet Tsuchinshan–ATLAS this year (if it survives!), our guides to the best telescopes and binoculars are a good place to start. And if you’re looking to take starry photos of the night sky, check out our guides to photographing comets , or our recommendations for the best cameras for astrophotography and the best lenses for astrophotography.
Who do we believe?
Because Dr. Sekanina is highly respected in the field, everything he says carries a lot of weight in astronomical circles. Yet his thoughts on the future of the approaching comet have been received with faith and conviction mixed with skepticism and uncertainty.
One person who had high hopes for a great show from Tsuchinshan-ATLAS, but now seems to have changed his mind based on Dr. Sekanina’s conclusion, is Joseph Marcus, a pathologist with a longtime interest in comets. While a resident at Washington University in St. Louis, he founded and edited the quarterly Comet News Service, published by the McDonnell Planetarium from 1975 to 1986. In an email to Space.com, Dr. Marcus writes:
“Sekanina’s case is compelling. In the unlikely event that C/2023 A3 survives perihelion, it would see an increase in brightness of almost 7 magnitudes.” (equivalent to a brightness increase ratio of almost 600-fold). “But,” he adds, “it is now a moot point. I bet on disintegration, as Sekanina now advocates, and to whom I leave it unconditionally. Ultimately, the comet will soon be no more.”
But others are not yet convinced.
Nick James, director of the British Astronomical Association’s Comet Section, says that while Sekanina’s paper is “fascinating,” he finds no evidence of non-gravitational accelerations. “This doesn’t look to me like a comet is fragmenting,” he says.
Another skeptic is Dr. Clay Sherrod of the Arkansas Sky Observatories on Petit Jean Mountain. “The comet isn’t going anywhere; it’s fine and not fragmenting, in my opinion,” he notes.
Looking “healthy”
Following Dr. Sherrod and Mr. James, Taras Prystavskian amateur astronomer living in Lviv, Ukraine who enjoys photographing various celestial objects, including comets. He provided Space.com with an image of Tsuchinshan-ATLAS taken on July 9, with the comment: “To me, the comet looks healthy. Some images also show an ion tail, but very faint. I know that an ion tail indicates that the comet nucleus is healthy. So there is a small hope to see a great show in the fall.”
Finally, there is Daniel Green of the Central Bureau for Electronic Telegrams (CBET), who cautiously writes: “I think the comet looks healthy and is now showing an ion tail. I see no evidence that this comet is breaking up, so all we can do now is wait and see. We will know by the end of September (or perhaps a little earlier) whether it will be a nice comet in October.”
Predicting the future is hard!
The late, great baseball expert Yogi Berra once said, “It’s hard to make predictions, especially about the future.” Those words certainly apply when predicting what a new comet might do.
While it is true that the brightness of Comet Tsuchinshan-ATLAS was more or less stable from mid-April to late June at magnitude +10.5, there are signs that the brightness (based on the Comet Observation Database/COBS) slowly starts to pick up again in the first half of July.
Telescopes reveal that the comet’s dusty head, or coma, has swollen to a linear diameter of about 180,000 miles (290,000 km), while its tail is now about 1.6 million miles (1.6 million km) long. Unfortunately, the comet is now too close to the sun’s glare for observers in the Northern Hemisphere to observe; in the coming weeks, only those living south of the equator will be able to watch its future progress.
Currently, the comet is about 158 million miles (254 million km) from the sun and is experiencing temperatures of about -150°F (-100°C). It is now beginning to cross the “water line,” where frozen gases sublime into vapor. If it manages to survive perihelion on September 27 (which Dr. Sekanina does not expect), it will be exposed to temperatures of over 1,000°F (1,600°C).
Analogy of hot tea
Picture this: Here we have a chunk of matter that probably dates back to the beginning of the solar system, nearly 5 billion years ago, that has been locked in an incredibly cold environment with temperatures hovering around absolute zero for all that time. Yet over the coming weeks it will encounter increasingly high temperatures of many hundreds of degrees.
What happens when you pour hot tea into a cold glass?
That’s what could happen to Comet Tsuchinshan-ATLAS in the coming weeks: the comet could break into pieces and fall apart completely.
No foregone conclusion
Does this mean, as Dr. Sekanina titled his paper, that it is a “Inevitable endgame” for comet Tsuchinshan-ATLAS?
Not necessary.
In November 2011, Australian amateur astronomer Terry Lovejoy discovered a very small comet, whose nucleus was only 500 meters in diameter and which only 87,000 miles (140,000 km) from the surface of the sun. It was not expected to survive and yet somehow it did, briefly giving a very nice visual spectacle for observers in the Southern Hemisphere (a short time later, after orbiting the Sun, Comet Lovejoy did indeed disintegrate as it flew back into space).
And in 1996, a comet that was being promoted as a “can’t miss” spectacle headed toward the sun suddenly and inexplicably stopped brightening from the first week of July until mid-October. Then, the comet suddenly got back on track and brightened, but just as quickly the brightness faded away again by mid-November. Some worried that the comet would be a flop. But by the spring of 1997, all fears were dispelled as the comet developed into a magnificent celestial showpiece.
What is the name of the comet? Hale-Bopp.
So maybe Yogi was right when he made predictions about the future is difficult. And perhaps the only thing we can do now, as Daniel Green suggests, is to adopt a “wait and see” attitude as to what Tsuchinshan-ATLAS will do in the coming days and weeks. It may, as Dr. Sekanina predicts, fall apart, but for now it is still whole and hearty.
And to achieve that goal, I want to mention one last yogi-ism:
“It’s not over until it’s over!”
Joe Rao is a lecturer and visiting professor at New York’s Hayden PlanetariumHe writes about astronomy for journal of natural historythe Farmers’ Almanac and other publications.