by A new comet was discovered in January 2023. Comets are found regularly, but astronomers soon realized that this one, named C/2023 A3 (Tsuchinshan-ATLAS), had the potential to be quite bright.
Some hyperbolic reports have suggested that this might be the “comet of the century”, but any astronomer will tell you that the brightness of comets is notoriously difficult to predict. As I explained last year, we had to wait for it to arrive to be sure how bright it would be.
Now the time has come. Comet C/2023 A3 is currently visible to the naked eye in the morning sky in Australia and Aotearoa New Zealand, and the best yet will occur in the coming weeks.
And it looks promising. It’s unlikely to be the comet of the decade (let alone the comet of the century), but it will almost certainly be the best comet of the year.
So where and when should you look to get the best view of this heavenly visitor?
So far, Comet Tsuchinshan-ATLAS looks like a faint star to the naked eye when you look out the dome windows. But with a 200mm, f2 lens at a 1/8 second exposure you can really start to see it. This comet will provide some very cool images as it gets closer to the sun. For now a… pic.twitter.com/JstaSLJ4Ui
— Matthew Dominick (@dominickmatthew) September 19, 2024
A show in the morning, before sunrise
Currently, Comet C/2023 A3 (Tsuchinshan-ATLAS) is a morning object that rises about an hour and a half before sunrise. It is visible to the naked eye, but not yet spectacular. However, with binoculars you can easily see the comet’s dusty tail pointing away from the sun.
The comet will remain at about the same height in the morning sky until about September 30. It will then move closer to the horizon each successive morning until it is lost in the glare of the approaching dawn on October 6 or 7.
To see the comet in the morning sky, look to the east. The sliders below will help you get your bearings and choose the best time to watch depending on your latitude.
During this period, the comet should slowly brighten. It reaches its closest approach to the Sun (perihelion) on September 27, when it is 58 million kilometers from our star.
As it orbits the sun, it will continue to approach Earth and thus become brighter. The best show in the morning sky will likely occur during the last few days of September and the first few days of October, before the comet is no longer visible.
A potential daylight comet
By sheer luck, Comet C/2023 A3 (Tsuchinshan-ATLAS) will pass almost directly between Earth and the Sun on October 9 and 10.
This could cause a spectacular brightening of the comet, thanks to the “forward scatter” caused by its dust. Imagine looking through a cloud of dust grains at a bright light source. The grains closest to the light source will scatter the light from the source towards you.
As the comet passes between Earth and the Sun, it is in the perfect position for this forward scattering process to take place. If the comet is particularly dusty, its apparent brightness can increase by up to 100 times.
If so, there is a small chance that the comet will briefly become visible in the daylight sky on October 9 and 10.
However, it will be very close to the sun in the sky and be incredibly difficult to spot. Only the most experienced observers could possibly detect the comet at this point, and that requires special technique. Don’t try to stare at the sun to see it.
The best show could be after October 12th
After swinging between Earth and the sun, the comet will appear in the evening sky. It is rapidly climbing in the western sky and should be a bright naked-eye object for a few days beginning on October 12. The sliders below will give you an idea of where to look.
For the first few days of this period, the comet will still benefit from the forward scattering of sunlight, but this will diminish as it moves further away.
What about the tail?
The positioning of the comet, Earth and Sun in the solar system means that the comet’s tail will flow outward, past our planet. This means it can grow to enormous lengths in the night sky.
Most of that tail will likely be too faint to easily see with the naked eye, but for photographers it could be an amazing sight. Expect a wealth of comet images to flood the internet in mid-October.
As the days pass and the comet climbs higher, it will fade away quite quickly. It will probably become too faint to see with the naked eye before the end of October, even for seasoned and experienced observers.
At that point the show will be over. Comet C/2023 A3 (Tsuchinshan-ATLAS) will continue to flee the inner solar system and head into the icy depths of space, never to return.
How reliable are the predictions?
At this point, the comet is already bright enough to be considered the “comet of the year,” surpassing Comet 12P/Pons-Brooks from earlier this year.
But remember the classic saying: comets are like cats. They have tails and will often surprise us. For now, comet C/2023 A3 is behaving. It predictably brightens and puts on a good show.
But comets that come this close to the sun often fragment. This is impossible to predict and far from guaranteed. If the comet were to burst, it could become even more spectacular because of all the dust and gas it would release.
The opposite could also happen. The comet may not be as bright as we expect, although that seems unlikely at this stage.
Whatever happens, we’re going to have a fascinating few weeks of comet watching. Hopefully a real spectacle awaits us.
Jonti Horner, Professor of Astrophysics, University of Southern Queensland
This article is republished from The Conversation under a Creative Commons license. Read the original article.
