Astronomers have just discovered a comet that could be brighter than most stars when we see it next year. Or will she?

Astronomers have just discovered a comet that could be brighter than most stars when we see it next year

Comets are rarely as bright as this illustration. Credit: IgorZh/Shutterstock

On the heels of a disappointing green comet, astronomers have just discovered a new comet that has the potential to be next year’s big story — C/2023 A3 (Tsuchinshan-ATLAS).

Although more than 18 months have passed since its closest approach to Earth and the Sun, comet Tsuchinshan-ATLAS is already making a splash on social media, with optimistic articles being written about how this will happen. A wonderful sight. What’s the whole story for this new snowy hiker?

Rendering of Comet C/2023 A3 (Tsuchinshan-ATLAS)

Every year, a few dozen new comets are discovered – sloppy snowballs that move in extremely long trajectories around the Sun. The vast majority are too faint to see with the naked eye. Perhaps one comet per year comes close to the edge of naked-eye visibility.

Occasionally, a brighter comet will come along. Because comets are objects of ephemeral, fleeting beauty, spotting a comet with potential always leads to excitement.

Comet C/2023 A3 (Tsuchinshan-ATLAS) certainly fits the bill. It was discovered independently by astronomers Purple Mountain Observatory in China and the The last alert system for an asteroid collisionComet Atlas is currently located between the orbits of Jupiter and Saturn, a billion kilometers from Earth. It is falling inward, moving in an orbit that will bring it within 59 million kilometers of the sun in September 2024.

The fact that the comet was detected so far away is part of why astronomers are so excited. Although it is currently about 60,000 times too faint to see with the naked eye, the comet He is bright of something very far from the sun. Observations indicate that it is following an orbit that could allow it to become truly spectacular.

A recipe for guilty pleasure

It all comes down to a combination of the comet’s trajectory through the solar system, and the likely size of its nucleus – the solid center.

As comets swing close to the sun, their temperature rises and their ices sublimate (turn from solid to gas). This gas blows off the comet’s surface, carrying away dust, shrouding the nucleus in what’s called a coma – a giant cloud of gas and dust. Then the coma is pushed away from the sun solar windresulting in a tail (or tails) pointing directly away from the sun.

Astronomers have just discovered a comet that could be brighter than most stars when we see it next year

Comet Tsuchinshan-ATLAS position plotted on March 10, 2023. Credit:

The closer a comet is to the Sun, the hotter its surface and the more active it is. Historically, the vast majority of the brightest and most spectacular comets have followed orbits that brought them closer to the Sun than Earth’s. The closer, the better, and Tsuchinshan-ATLAS certainly ticks that box.

In fact, this new comet seems to tick all the boxes. It appears to have a large core, which makes it much brighter (bright enough to be detected far from the Sun). She is destined to have a very close encounter with our star. And, ejecta, it will then pass almost directly between the Earth and the Sun, approaching within 70 million km of us only two weeks after perihelion ( closest approach to the sun). The closer a comet is to Earth, the brighter it appears to us.

Put that together, and you have a recipe for a comet that can shine like the brightest star. Some predictions are even more optimistic, suggesting they could be up to a hundred times brighter!

The curse of prediction

“Comets are like cats: they have tails, and they do exactly what they want,” said astronomer David H. Levy.

Predicting the behavior of newly discovered comets is a dangerous game. Some of them may be amazing, while others are fading.

take this example, Comet Kohoutekin 1973. Like Tsuchinshan-ATLAS, Kohoutek was detected unusually far from the Sun, moving in an orbit that teeters close to our star. Cue the noise. Astronomers promised the publicComet of the centuryKohoutek was expected to become bright enough to see in broad daylight.

But comets are like cats. Kohoutek brightened as he swung toward the sun, but more slowly than expected. Instead of being visible in broad daylight, it was Just Shiny as the brightest star, quickly fading after perihelion. It was still a good show, but far from the comet of the century. Because of the hype, many called Kohotek an amazing disappointment.

It turns out that Kohotek was passing through the inner solar system for the first time. It had never come close to the Sun, so its surface was rich in highly volatile ices that began topping up 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 amazing.

As it got closer to the Sun, that volatile material was depleted, and the comet’s final activity was less than initially expected, causing it to dim.

Astronomers have just discovered a comet that could be brighter than most stars when we see it next year

A schematic view of a comet, not scale, showing the comet’s nucleus (a), coma (b), and tails of gas and dust (c and d). These tails always point away from the Sun (which is in the g-direction) no matter how the comet is moving (the f-direction in the figure). Credit: Sanu N/Wkimedia Commons, CC BY-SA

There’s a very real chance Tsuchinshan-ATLAS, like Comet Kohoutek, may be approaching the inner solar system for the first time. We’re not sure yet – but if that’s the case, it might also end up being less exciting than expected.

Where everything collapses

But it could be worse. Comets are prone to disasters. They crumble, fall apart, and fall apart surprisingly often. Those who come to the inner solar system for the first time are particularly vulnerable.

A recent example of such fragmentation is the comet C/2020 F8 (SWAN). When SWAN was detected, it looked promising — likely to become a naked-eye object in May 2020. But as it got closer to the Sun, it suddenly brightened, then became fuzzy, and began to fade. By the time it should have been brighter, it had completely disappeared, having crumbled before our eyes.

On the flip side, fragmentation events can sometimes turn a good comet into a great one. Three years after the advent of Kohotek Comet C/1975 V1 (West)and he He was Really amazing.

It passed much closer to the Sun than Tsuchinshan-ATLAS did – and was already dazzling when, at perihelion, its core shattered into four pieces. This fragmentation event released a huge amount of gas and dust, and the comet brightened remarkably, until it became visible in broad daylight.

Is Tsuchinshan-ATLAS worth the anticipation?

We won’t know for sure if the Tsuchinshan-ATLAS comet will be a sight until it arrives. It can collapse and become less bright, or it can surprise us.

It could light up more than expected – making for a nice view in the morning sky in late September and early October 2024, and an even better view in the evening sky in mid-October 2024

We just don’t know. But we’ll get our first hints in the coming months. by Trace how the comet shines When it slides toward the sun, we’ll get our first clues to its true fate — so keep your fingers crossed.

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