by This article was originally published by The conversation. The publication contributed the article to Space.com’s Expert Voices: Tutorial & Insights.
Jonty Horner is an astronomer and astronomer based at the University of Southern Queensland, in Toowoomba, Queensland.
Astronomers have just discovered a new comet that could be a big story for next year – C/2023 A3 (Tsuchinshan-ATLAS).
Although it is still more than 18 months from its closest approach to Earth and the sun, comet Tsuchinshan-ATLAS is already buzzing social media, with optimistic articles being written about how it could be a spectacular sight .
What is the full story on this new icy slope?
Related: Bright new comet found zooming towards the sun could pass the stars next year
Introducing Comet C/2023 A3 (Tsuchinshan-ATLAS).
Every year, a few dozen new comets are discovered – dirty snowballs moving on very long paths around the sun. Most are far too faint to see with the unaided eye. Perhaps one comet per year approaches the edge of visibility to the naked eye.
Occasionally, however, a comet will become much brighter. Because Comets are short-lived and impermanent beauties, there is always excitement in finding a comet with potential.
Comet C/2023 A3 (Tsuchinshan-ATLAS) certainly fits the bill. Independently discovered by astronomers at the Purple Mountain Observatory in China and the Asteroid Terrestrial Impact Early Warning System, ATLAS, the comet is currently between the orbits of Jupiter and Saturn, a billion kilometers from Earth. It is falling in, moving into an orbit that will bring it within 59 million kilometers of the sun in September 2024.
Part of the reason for the astronomers’ excitement is that the comet was found so far away. Although currently about 60,000 times too small to be seen with the naked eye, the comet yes bright from something so far from the sun. And comments suggest that it is following an orbit that could allow it to be truly spectacular.
Recipe for comet greatness
It all comes down to a combination of the comet’s path through the solar system, and the potential size of its nucleus – the solid center.
As comets move closer to the sun, they rise, and their surface ices sublimate (turn from solid to gas). Erupting from the comet’s surface, this gas carries dust, enveloping the nucleus in what is called a coma – a huge cloud of gas and dust. The Coma is then pushed away from the sun by the solar wind, resulting in a tail (or tails) pointing directly away from the sun.
The closer a comet gets to the sun, the hotter its surface will become, and the more active it will become. Historically, the vast majority of the brightest, most prominent comets followed orbits that brought them closer to the sun than Earth’s orbit. The closer, the better, and Tsuchinshan-ATLAS certainly ticks that box.
Indeed, this new comet seems to tick all the boxes. It appears to have a large nucleus, which makes it brighter (bright enough to be so far from the Sun). We are destined to have a very close encounter with our star. And, the kicker, it will pass almost directly between Earth and the sun, coming within 70 million kilometers of us just two weeks after perihelion (closest approach to the Sun). The closer a comet comes to Earth, the brighter it will appear to us.
Put that together, and you have a recipe for a comet that could be as bright as the brightest stars. Some forecasts are even more bullish, suggesting it could be up to a hundred times brighter!
The curse of prophecy
Predicting how newly discovered comets will behave is a dangerous game. Some may be great, and others fizzle.
Take, for example, comet Kohoutek, in 1973. Like Tsuchinshan-ATLAS, Kohoutek was discovered unusually far from the Sun, moving in an orbit that swung close to our star. Cue the hype. Astronomers promised the public the “comet of the century,” predicting that Kohoutek could become bright enough to be seen in daylight.
But comets are like cats. Kohoutek glowed as he swung into the sun, but more slowly than expected. Rather than being seen in broad daylight, it was only as bright as the brightest stars, and quickly faded after the perihelion. It was still a good show, but far from the comet of the century. Because of the hype, many Kohoutek called it a great disappointment.
It turns out that Kohoutek was passing through the inner Solar system for the first time. It never came this close to the sun, so its surface was rich in highly volatile ice that began to flow when the comet was still far away. At that great distance, the comet was much brighter than other more experienced comets – and that brightness indicated that the comet would be truly spectacular.
As it got closer to the sun, those fluctuations were exhausted, and the comet’s final activity was less than originally predicted, making it fainter.
There is a very real chance that Tsuchinshan-ATLAS, like Kohoutek’s comet, could be approaching the solar system within the first hour. We’re not sure yet – but if so, it might be less spectacular than predicted.
Where it all comes together
But it could be even worse. Comets can be catastrophic. They separate, they fall apart, and they separate surprisingly often. Those entering the inner solar system for the first time are particularly vulnerable.
A recent example of such fragmentation was comet C/2020 F8 (SWAN). When SWAN was discovered, it looked very promising – it was likely to become a visible object in May 2020. But as it approached the sun, it suddenly brightened, then dimmed. , and it started to get worse. By the time it should have been brighter, it was almost gone, having fallen apart before our very eyes.
On the flip side, fragmentation events can sometimes turn a good comet into a great one. Three years after Kohoutek came comet C/1975 V1 (West), and it was really amazing.
It passed closer to the sun than Tsuchinshan-ATLAS would – and was already obscured when its nucleus broke into four pieces at the edge. That fragmentation event released an enormous amount of gas and dust, and the comet was remarkably bright, even visible in daylight.
Is Tsuchinshan-ATLAS worth a look?
RELATED STORIES:
— Watch ‘Devil Comet’ approach the sun during a massive coronal explosion (video)
— Solar spacecraft ‘SOHO’ discovers its 5,000th comet
— Halley’s Comet begins its 38-year journey back toward Earth tonight
We won’t know for sure if comet Tsuchinshan-ATLAS will be a show until it arrives. It could collapse and become less lunar, or it could surprise us.
It could be brighter than expected – making for a great view of the morning sky in late September and early October 2024, and an even better view in the evening sky in mid-October 2024.
We don’t know. But we will get our first clues in the coming months. By tracking the comet’s rise as it passes through the sun, we’ll get our first clues as to its true fate – so keep your fingers crossed.
Read the basic article at The Conversation.
