Sublime spectacle: this comet will be visible to the naked eye!
To Digitalwe don't want to disappoint you. But really, this comet has everything to be unforgettable. Around October 12, 2024, it will become the jewel of the southwest horizon at sunset with its white dust hair and blue tail.
All the forecasts agree to offer a show capable of marking as much, if not more, than that of 1997 with Hale-Bop.
The incredible and gigantic dust tail of the comet McNaught in 2006, taken at Mount Paranal (ESO) © S. Deiries/ESO
Neowise, the last comet visible to the naked eye in 2020, was 40 times less bright than the most optimistic predictions for C/2023 A3! © Bob King
The icy star from the outer reaches of the Solar System, beyond the orbit of Jupiter, is currently reaching the crazy speed of 270,000 km/h relative to Earth. It will soon be at its closest to our star, on September 27, then to Earth on October 12. At that time, its luminosity will be optimal with a magnitude estimated between 0 and -5.
At the end of September, we could see it with the naked eye in the morning to the right of the rising Sun, around 6:50 a.m. Yes, but it will not be the ideal time…
Simulation of the position and brightness of C/2023 A3 on the morning of September 27. © Stellarium Software.
It is only from the beginning of October that the comet will appear before us in the evening, in full light, in the northern hemisphere. Each evening, it will be a little higher on the horizon.
Simulation of the position and brightness of C/2023 A3 at sunset on October 14. © Stellarium Software.
If it lives up to its promise of brightness, the spectacle could be even more incredible than the passage of Hale-Bopp in 1997. The comet could actually become about six times brighter than the latter, thus becoming perfectly visible to the naked eye in broad daylight (magnitude of up to -4 or -5 for C/2023 A3 and -1.9 for Hale-Bopp).
But why are they so sublime?!
Because comets sublimateprecisely. Explanation…
Comet comes from the Greek comets which refers to the hair, this famous white and blue hair that characterizes them so well. A comet is like an asteroid several kilometers across filled and covered with ice. The closer this large frozen mountain gets to the Sun — and therefore to us —, the more its ice melts, releasing this immense tail of white dust. This is the principle of sublimation: passing from the solid to the gaseous state without passing through the liquid phase.
But when the comet is close enough to the Sun, the interaction with its particles produces another, even more spectacular effect. The blue tail of plasmacalled “ionic” which is always opposite the Sun. Here is a very nice simulation of the orbit of C/2023 A3:
Simulation of the orbit of C/2023 A3 as a function of date. (Pepe Chambó's website). © Animation of Pepe Chambó on the simulator courtesy CSS, D. Rankin
Anatomy of a comet with its two main tails. © Vito Technology, inc. Starwalk
Don't miss this treasure of space if the skies are not too cloudy and if the comet continues to live up to its promises, which seems to be very well on its way. For the author of these lines, seeing Hale-Bopp with the naked eye one day in April 1997 was the first great astronomical emotion and surely played a big part in his passion for the skies and science. A comet can change a life!
Let us remember that, despite everything, you never know with comets… As the saying goes so well @Astropierre on X-Twitter, “Comets are the cats of space: they do what they want, when they want!”
