Will This Be the Best Comet of 2025?
By Graham Jones. Published 7-Jan-2025
Comet C/2024 G3 (ATLAS) has started to become very faintly visible to the naked eye for observers in the Southern Hemisphere.
This view from our Night Sky Map for Sydney shows the position of C/2024 G3 (ATLAS) just before 21:00 (9 pm) on January 18. Above and to the right, Venus shines brightly next to Saturn. The size of objects on our Night Sky Map is exaggerated to show their positions more clearly.
©timeanddate.com
A Bright Comet for the Southern Hemisphere?
Skywatchers in the Southern Hemisphere are keeping a careful watch on the “sunskirter” comet C/2024 G3 (ATLAS), which might be the brightest comet of 2025.
C/2024 G3 (ATLAS) will reach perihelion—its closest point to the Sun—on January 13, 2025.
Can We See the Comet?
Before January 13, C/2024 G3 (ATLAS) might be visible from the Southern Hemisphere close to the eastern horizon before sunrise.
Find comet C/2024 G3 (ATLAS) on our Night Sky Map
According to reports from observers, the comet started to become very faintly visible to the naked eye, under good viewing conditions, around January 3.
After January 13, C/2024 G3 (ATLAS) might be visible close to the western horizon after sunset—again, from the Southern Hemisphere.
For skywatchers in the Northern Hemisphere, the comet will likely not be visible.
The brightness of comets is notoriously hard to predict, and comets can be destroyed altogether as they pass close to the Sun.
How Close Is Close?
Sunskirter comets pass close to the Sun, although not quite as close as sungrazers.
Perihelion distances are often given in astronomical units (au), where 1 au is equal to Earth’s average distance from the Sun.
At perihelion, the distance of C/2024 G3 (ATLAS) from the Sun will be 0.09 au, making it a sunskirter. Sungrazer comets pass within around 0.01 au of the Sun.
ATLAS: Have We Heard That Name Before?
C/2024 G3 (ATLAS) was discovered on April 5, 2024, by a robotic system of telescopes called the Asteroid Terrestrial-impact Last Alert System, or ATLAS for short.
The ATLAS team has discovered around 100 comets, which is why the name might seem familiar.
For example, you may remember C/2023 A3 (Tsuchinshan-ATLAS), which dazzled skywatchers in October last year. Or C/2024 S1 (ATLAS), which disintegrated as it reached perihelion.
What Are the Rules for Comet Names?
The name C/2024 G3 (ATLAS) is based on a set of rules from the International Astronomical Union.
- C/ refers to a non-periodic comet. This means the comet hasn’t been observed before, and its orbital period (the amount of time it takes to complete one orbit around the Sun) is greater than 200 years. The orbital period of C/2024 G3 (ATLAS) runs into hundreds of thousands of years.
- 2024 is the year the comet was discovered.
- G indicates the half-month it was discovered—in this case, the first half of April. The first half of January is “A,” the second half of January is “B,” the first half of February is “C,” and so on. The letter “I” is skipped to avoid confusion with the number “1.”
- 3 means it was the third comet discovered in that half-month.
- ATLAS is the name of the team that made the discovery.