In a year in which we’ve already been treated to the “Great North American Solar Eclipse” in April and one of the greatest Northern Lights shows in the last 500 years in May, what other amazing celestial attractions will 2024 have? could she book us? ?
How about a bright comet visible to the naked eye?
Over the past two years, two comets have made headlines in the mainstream media. At the beginning of February 2023, Comet C/2022 E3 (ZTF)unofficially called the “Great Green Comet”, passed close to Earth and then, over the past month, Comet 12P/Pons-Brooks has attracted attention due to its propensity to experience a sudden burst of brightness and appear to emit horn-like gaseous appendages, thus giving rise to the nickname “Devil’s Comet”.
The only problem for the man in the street was that the two comets were difficult to see unless located under a dark, light-polluted sky. And even with good binoculars or a small telescope, both were rather unimpressive, appearing as nothing more than faint, fuzzy patches of light.
Related: A comet arriving in 2024 could eclipse the stars – if we’re lucky
Bright? Easy to see?
But by the end of summer, we may have a good idea whether we’ll have a bright, easy-to-see-with-the-naked-eye comet gracing our early fall sky. The comet in question is C/2023 A3 (Tsuchinshan-ATLAS), discovered by the Asteroid Land Impact Warning System (ATLAS) in South Africa on February 22, 2023. ATLAS is a robotic early warning system developed specifically to detect terrestrial asteroids a few weeks to days before they impact Earth.
Initially thought to be an asteroid, it was later determined that this same object had been photographed six weeks earlier by the Purple Mountain Observatory (Tsuchinshan), east of Nanjing, China. It has since been determined that it was actually an incoming comet.
When the comet was first sighted, it was well beyond Jupiter’s orbit, about 680 million miles (1.09 billion kilometers) from the sun. But on September 27 this year, Tsuchinshan-ATLAS will come closest to the sun, within 58 million kilometers. This is also the average distance of the planet closest to the sun, Mercury.
And just over two weeks later, on October 12, the comet will pass just 71 million kilometers from Earth.
These figures suggest that the comet could reach second or even first magnitude, and could develop a remarkable tail that could make for an eye-catching sight in the western evening sky in mid-October 2024.
Learn more: How to see and photograph comets
It could also be a failure
Unfortunately, there is a caveat: calculations show that Tsuchinshan-ATLAS has an orbital eccentricity of 1.0001081, meaning it is a “first comer”, coming directly from the Oort Cloud , a spherical shell of icy space debris that scientists theorize is located far beyond the outer limits of the solar system and is thought to contain billions, if not trillions, of comets.
Comets from the Oort Cloud have never passed close to the sun before and their cores are covered in highly volatile material that vaporizes away from the sun, creating short-lived bursts of brightness. But as these comets get closer to the sun, their brightening slows or even stops altogether.
Most – but certainly not all – comets originating from the Oort Cloud usually end up being missed. Typically, as these comets pass through Mars’ orbit, their steady brightening trend begins to falter, like a marathon runner at the 20-mile mark; “hit the wall” so to speak. In the case of a comet that has emerged from the Oort Cloud, a sudden drop in its brightening could indicate that it will eventually underperform.
Not before midsummer
Comet Tsuchinshan-ATLAS will not reach this point in its orbit until the end of July. If it continues to clear steadily beyond this period, there is a good chance that it will become an eye-catching spectacle. But, more likely, if its thinning trend suddenly slows or even stops, all bets for a good show are off. In the meantime, all we can do is wait and watch.
Unfortunately, here in the Northern Hemisphere, we will not be able to check the state of comet Tsuchinshan-ATLAS this summer because it will be located far too far south to be accessible with telescopes. However, those living in areas far south, such as Australia, New Zealand and South America, will be able to follow it in the morning sky before sunrise.
We will have to rely on reports from these regions of the globe to tell us whether the comet is on its way to becoming a bright object.
Dusty highlights are the key to a good show
Another thing that could work in our favor is that the comet’s geometry relative to the Sun and Earth places it almost between the Sun and Earth around October 8, creating a phenomenon known as “scattering.” ‘before sunlight’. If the comet is particularly dusty, dust particles ejected from the comet’s nucleus would preferentially scatter sunlight forward and could cause a dramatic increase in the comet’s brightness.
To this end, there are two comets that Tsuchinshan-ATLAS could be compared to, which suddenly brightened due to forward scatter. The first was comet Skjellerup-Maristany (C/1927 the sunlight. with the hand; it has since been classified among the greatest comets of all time.
The other comet was Comet McNaught, also known as the Great Comet of 2007 and designated C/2006 P1, and was the brightest comet in over 40 years; easily visible to the naked eye to observers in the Southern Hemisphere during January and February 2007. At its peak on January 12, 2007, this comet appeared at least twice as bright as Venus and, like Skjellerup-Maristany, was visible all over the world in a broad perspective. daylight next to the sun. This extreme brightness was also attributable to forward scatter.
Some calculations suggest that Tsuchinshan-ATLAS could become as bright as Venus around October 8, 2024 – although in the sky – like the 1927 and 2007 comets – it is also very close to the position of the sun. However, in the following days, Tsuchinshan-ATLAS is expected to move rapidly northward and become well-positioned for observation in the western sky by mid-October. Although it will now fade as it moves away from the Sun and Earth, it will hopefully be bright enough to be seen well with the naked eye, perhaps also accompanied by a remarkable tail.
No guarantee
But there are no guarantees. In the past, there have been comets that seemingly promised a great show but failed to live up to expectations. Comet Faucet from 1973-74 is a good example. Conversely, there have been comets that seemed underperforming and ended up unexpectedly becoming celestial showpieces. Comet NEOWISE surprised everyone during the summer of 2020 by putting on a good show.
Legendary comet expert Dr. Fred Whipple perhaps said it best when he said:
“If you have to bet, bet on a horse, not a comet!”
In the meantime, fingers crossed for Comet Tsuchinshan-ATLAS! Stay tuned to Space.com for future updates.
Joe Rao is an instructor and guest lecturer at New York University Hayden Planetarium. He writes on astronomy for Natural history reviewTHE Farmers’ Almanac and other publications.