A "once-in-a-lifetime" comet, which is also the brightest in 13 years, will be visible in UK skies during October.

Comet C/2023 A3 (Tsuchinshan-ATLAS) was first discovered early last year by ATLAS (Asteroid Terrestrial-impact Last Alert System) and the Purple Mountain Observatory in China.

Now, nearly two years later, the comet is set to orbit close enough to the earth that it will be visible to the naked eye.

It may become so bright, you will even be able to see it during the day.

Star Walk, explaining the rare comet, said: "The tail is stretching a whopping 15 degrees across the sky—that's equal to the width of 30 Full Moons!

"The forward scattering effect on the comet's dust is kicking in, which is expected to boost its brightness even more in the coming 2-3 weeks."

When to see Comet A3 (Tsuchinshan-ATLAS) in UK skies

The best time to see Comet A3 (Tsuchinshan-ATLAS) in the UK and across the Northern Hemisphere will be between October 12 and 30, according to Star Walk.

The best visibility will come "just after sunset".

The comet is set to reach a magnitude of -5 by October 9, which could make it bright enough for daytime observation.


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Comet A3 (Tsuchinshan-ATLAS) among the brightest in last 60 years

Comet A3 (Tsuchinshan-ATLAS) is the brightest comet in 13 years, according to Star Walk, having overtaken NEOWISE from 2020 with current estimates of a 0.4 magnitude.

The night sky experts added: "Predictions for this comet to become the brightest of the Northern Hemisphere in the 21st century are looking more and more likely."

It is also among the brightest comets in the past 60 years, Sky Walk added.


The brightest comets in the last 60 years

  • Comet Ikeya-Seki, -10 mag (1965)
  • Comet West, -3 mag (1975)
  • Comet Hale-Bopp, -1 mag (1997) 
  • Comet NEAT, -1 mag (2003)
  • Comet McNaught, -5 mag* (2007)
  • Comet Lovejoy, -3 mag* (2011)
  • Comet NEOWISE, +1 mag (2020)

(* = visible only in the Southern Hemisphere)


The experts said: "Don't miss out on this once-in-a-lifetime spectacle! Keep your eyes on the sky!"

Comet A3 (Tsuchinshan-ATLAS) is set to be visible in UK skies between October 12 and 30, 2024.