The ATLAS survey telescope has detected a comet approaching the sun just as skywatchers and astronomers are preparing to see and photograph Comet C/2023 A3 (Tsuchinshan-ATLAS), which should be a naked eye object after sunset for a few weeks beginning around Oct. 9.

The new comet, initially named A11bP7I and now called C/2024 S1 (Atlas), appears to be unusually large and could become a “significant naked eye object by the end of October,” according to SpaceWeather.com.

C/2024 S1 (Atlas) is expected to make its closest approach to Earth on Oct. 23 and have its perihelion with the sun — the closest it will get to our star — just five days later on Oct. 28. That latter date looks set to be the best time to observe it because it may shine at a brightness of magnitude -8.3. That’s extraordinarily bright, brighter even than Venus, the brightest object in the sky aside from the sun and moon.

However, there is a significant caveat. Comets are unpredictable and can disintegrate as they get close to the sun. The critical date for C/2024 S1 (Atlas) is Oct. 28, its perihelion. It must survive to become a genuinely bright object and to become visible to anyone in the Northern Hemisphere.

Comet C/2024 S1 (Atlas) is a long-period comet from the Oort Cloud — a sphere around our solar system home to millions of comets — and was discovered on Sept. 27, 2024, by astronomers at the the ATLAS survey, Hawaii.

C/2023 A3 (Tsuchinshan-ATLAS) — also known as comet A3 — has already had its perihelion with the sun on Sept. 27 and will get closest to Earth on Oct. 12. An evening or two before that latter date looks set to be the best time to observe it because it may shine bright enough to be seen with the naked eye.

For C/2023 A3 (Tsuchinshan-ATLAS), the prospects of being easy to see are more sure because it has already survived its perihelion. Favorable positioning means its dusty tail will likely reflect sunlight due to a phenomenon called “forward scattering” that sends reflected sunlight in the direction of Earth.

Comet C/2023 A3 (Tsuchinshan-ATLAS) is also a long-period comet from the Oort Cloud and visits the inner solar system roughly every 80,000 years. It was discovered in January 2023 by astronomers at China’s Tsuchinshan Observatory and South Africa’s Asteroid Terrestrial-impact Last Alert System (ATLAS) telescope.

Wishing you clear skies and wide eyes.