Of all the objects in the solar system, perhaps the most spectacular are the great comets that occasionally grace our skies. If you’ve been using social media in the past few days, you’ve probably seen articles announcing the presence of such a comet in our sky right now: C/2023 P1 (Nishimura).
As I write this, Comet Nishimura is passing by for its first visit in more than 400 years. Japanese astronomer Hideo Nishimura discovered the comet on August 12. Soon after, pre-discovery images of the comet dating back to January were found, allowing astronomers to determine its path.
They soon realized that Nishimura would swing closer to the Sun than to the orbit of Mercury this month. Given the comet’s brightness at the time of its discovery, it could become bright enough to be seen with the naked eye. Will it be an amazing sight in our skies? Probably not.
Unfortunately, Nishimura’s path will keep it as close to the Sun in the sky as observed from Earth. While it is certainly bright enough to be visible to the naked eye in a dark sky, at best it will hug the horizon just after sunset — almost getting lost in the sun’s glare.
However, astronomers around the world are excited. Even a comet that is difficult to see with the naked eye is worth observing. As science writer and astronomer David H. Levi He once said: “Comets are like cats: they have tails, and they do exactly what they want.”
Related: Will the newly discovered Comet Nishimura be visible to the naked eye? Experts aren’t so sure
There is a possibility that Nishimura could shine unexpectedly. If that happens, we might see something special in a couple of weeks. If not, there’s always next year – but more on that later.
Recipe for a bright comet
Comets are like cats: they have tails, and they do exactly what they want.”
— David Levy
When comets are far from the sun, in the icy depths of space, they are essentially dirty snowballs: clumps of ice, dust and rock left over from the formation of the solar system.
When a comet approaches the Sun, its surface begins to heat up. Snow near the surface becomes hot andSublime“, turns into gas and explodes outward from the comet’s surface. This gas carries dust and debris, enveloping the nucleus in a transparent cloud of gas and dust called the “coma.”
The solar wind then pushes the gas and dust away from the sun, giving the comet its tail (or tails). Tails always A point away from the sun.
The comet we see is sunlight reflected from the gas and dust in the coma and tails, and the nucleus itself is hidden from view. Thus, the brightness of a comet is usually determined by three things:
- Nucleus size: A larger nucleus usually means a larger active surface area (although some comets are more active than others) and the production of more gas and dust;
- Distance to the Sun: The closer a comet is to the Sun, the more active (and brighter) it becomes;
- Distance to Earth: The closer the comet is to us, the brighter it appears.
What about Nishimura?
This brings us to Comet Nishimura. It seems likely that Nishimura is not that large – otherwise we would have discovered it sooner – nor is it particularly close to Earth. However, it passes relatively close to the Sun and is expected to be very active around perihelion (the closest point to the Sun).
If it could be seen in the dark night sky, the comet would be very impressive. Unfortunately, even at his best, Nishimura will be close to the sun in the sky.
Moreover, the comet and Earth happen to be located in the worst viewing direction: Nishimura will remain close to the Sun as it recedes from us, and will remain buried in the star’s glare.
Short window to see Nishimura from Australia
Nishimura will soon peek over the western horizon after sunset, but only just. The best chance to see it from Australia comes in the week of September 20-27, when the comet’s head will set about an hour after sunset. It will be farthest from the sun in the evening sky on September 23.
As twilight ends, Nishimura will be very close to the western horizon, about to set. This means it will likely get lost in the glare of the sun.
But remember, comets are like cats. Some comets disintegrate when they are closest to the Sun, in which case they often shine noticeably. If that happened to Nishimura, it could become much easier to spot.
Unfortunately, the comets most susceptible to fragmentation are those visiting the inner solar system for the first time, moving on very long orbits of tens or hundreds of thousands of years. Nishimura is an experienced visitor, with a rotation period of about 430 years. It has likely passed the Sun several times and survived, making it less likely to disintegrate.
However, while the comet’s head may be lost in the twilight, the tail may still be visible as the sky darkens. Before the comet was lost in the glare of viewers in the Northern Hemisphere, observers identified its tail at about six degrees – likely to grow as the comet approaches the Sun.
If you’re lucky, you might notice the tail standing proud above the horizon as the sky darkens.
The next great comet
If Nishimura isn’t the show you were hoping for, there’s a chance another comet will put on a truly amazing show next year. Comet C/2023 A3 (Tsuchenshan-Atlas) It was discovered at the beginning of this year. It is currently almost as far from the Sun as Jupiter.
Over the next 12 months, it will continue to fall toward the sun, and will approach the sun in late September 2024. The Tsuchenshan-Atlas telescope looks promising. If they behave as expected, it could be an amazing sight – but just remember: comets are like cats!
Check out our guides to the best binoculars and the best telescopes to help you find the right telescope for you. And if you’re looking to take photos of Comet Nishimura or the night sky in general, check out our guide on how to photograph comets, as well as our best cameras for astrophotography and best lenses for astrophotography.
Editor’s note: If you took a photo of Comet Nishimura and would like to share it with Space.com readers, send your photo(s), comments, name and location to [email protected].
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