The recently discovered comet Nishimura (C/2023P1) has attracted public attention. While its trajectory suggests it would be close to the Sun and would be visible to the naked eye, it's unlikely to produce a celestial display, especially one as spectacular as this illustration.

Of all the objects in the solar system, perhaps the most spectacular are the great comets that occasionally appear in our skies. If you've scrolled through social media in the past few days, you may have seen a few articles claiming that there is now such a comet in our skies: C/2023P1 (Nishimura).

As I write this, comet Nishimura is swinging by for the first time in more than 400 years. Japanese astronomer Hideo Nishimura discovered the comet on August 12. Soon after, images of the comet, which had been spotted back in January, were discovered, allowing astronomers to determine its trajectory.

They soon realized that Comet Nishimura would swing closer to the sun than Mercury does this month. Given how bright the comet was when it was discovered, it's likely it will become bright enough to be seen with the naked eye. So, will it become a spectacular sight in our skies? Probably not.

This image of Comet Nishimura, taken on August 18 from June Lake, California, has a green tail and an elongated tail. Image source and copyright: Dan Bartlett Dan Bartlett

Unfortunately, Comet Nishimura's trajectory would keep it close to the Sun in the sky as viewed from Earth. While it's bright enough to be seen with the naked eye in a dark sky, at best it sticks to the horizon after sunset - nearly disappearing in the sun's rays.

Still, astronomers around the world are excited. Even comets that are difficult to spot with the naked eye are worth observing. As science writer and astronomer David H. Levy once said, "Comets are like cats. They have tails and they do what they want."

There's a chance the West Village could get unexpectedly bright. If so, we might be seeing something special in the coming weeks.

The secret to bright comets

As a comet moves away from the sun, deep in the icy depths of space, a comet is essentially a dirty snowball: a chunk of ice, dust and rock left over from the formation of the solar system.

As a comet approaches the sun, its surface begins to heat up. The ice near the surface becomes hot and "sublime," turning into gas and erupting outward from the comet's surface. These gases carry dust and debris, shrouding the comet's nucleus in a cloud of gas and dust known as the "tail."

The solar wind then blows gas and dust away from the sun, which forms the comet's tail. A comet's tail always points away from the sun.

The comet we see is sunlight reflected by the gas and dust in the comet's tail and tassel, and the comet core itself is hidden. Therefore, the brightness of a comet is usually determined by three aspects:

Size of the comet's nucleus: A larger nucleus usually means a larger active area (although some comets are more active than others) and produce more gas and dust

Distance from the Sun: The closer a comet is to the Sun, the more active (brighter) it is.

Distance from Earth: The closer a comet is to us, the brighter it becomes.

So what does Comet Nishimura look like?

Comet Nishimura doesn't appear to be very big -- otherwise we would have spotted it earlier -- and it's not particularly close to Earth. However, it is passing relatively close to the Sun and is expected to be very active near perihelion (the closest point to the Sun).

It would be impressive to see this comet in the dark night sky. Unfortunately, even in its best conditions, Comet Nishimura will appear close to the Sun in the sky.

In addition, the comet and the Earth happen to be in the most unfavorable positions for observation: when Comet Nishimura disappears from us, it will be close to the sun and continue to be obscured by the bright light of the star.

The West Village will soon reveal itself to the western horizon after sunset, but only just. The best time to see Comet Nishimura from Australia is during the week of September 20-27, when the comet's head sets about an hour after the sun sets. On September 23, the comet was farthest from the sun in the sunset. When dusk ends, "West Village" will be very close to the western horizon, about to set. That means it's likely to get lost in the sun's glare.

This image shows Comet Nishimura's position in the sky as seen from Toowoomba on the evening of September 23, 40 minutes after sunset. At this time, twilight was getting darker and the comet was only 5 degrees away from the western horizon. Image source: Screenshot/Stellarium

Some comets break up when closest to the Sun, in which case they tend to brighten significantly. If "West Village" were to encounter this situation, it would become easier to detect. Unfortunately, the comets most likely to break up are those making their first visits to the inner solar system, on long-period orbits of tens or hundreds of thousands of years. Comet Nishimura is an experienced visitor, with an orbital period of about 430 years. It likely passed by the sun multiple times and survived, which lowers the chances of it shattering.

Still, while the comet's head may disappear in twilight, the tail may still be visible when the sky darkens. Before northern hemisphere observers saw the comet disappear in the glare, observers thought its tail was about six degrees long -- a tail that may get longer as the comet gets closer to the sun.

If you're lucky, you might spot the comet's tail standing proudly above the horizon as the sky darkens.

the next great comet

If Comet Nishimura doesn't perform as expected, there's a chance another comet will put on a truly spectacular show next year. Comet C/2023A3 (Tsuchinshan-ATLAS) was discovered at the beginning of this year. Currently, it is almost as far from the sun as Jupiter.

It will continue its descent toward the Sun over the next 12 months, reaching its closest approach in late September 2024. Yishan-ATLAS looks promising. If it performs as expected, it will be a spectacular sight - but remember: comets are like cats!

Author: Jonti Horner, Professor, University of Southern Queensland (Astrophysics).

Adapted from an article originally published in The Conversation.