A pair of once-in-a-lifetime comets will rocket through our skies this October. It's a rare treat for skywatchers, as they won't be back again for hundreds of years.
The comets -- C/2025 A6 (Lemmon) and C/2025 R2 (SWAN) -- look similar from our perspective. You can spot these green gaseous globes and their streaming tails now. But the comets will be even easier to see later this month.
SWAN will shine the brightest around Oct. 20, NBC News reports. Just a day later, on Oct. 21, Lemmon will make its peak showing in the dark sky.
If you want to witness these comets shooting past Earth, the coming weeks will be the best time. There won't be another chance; the next time SWAN will come by again will be in 650 to 700 years, and Lemmon won't return for another 1,300 years, CNN reports.
Comets are known to buck even the most careful predictions, but wary observers might catch these rare spectacles in October from their backyards in the pre-dawn morning or night sky.
New comets on the scene
Lemmon and SWAN were both discovered in 2025. Lemmon was discovered on Jan. 3 in Arizona by the Mount Lemmon Survey -- using a 60-inch telescope installed on Mt. Lemmon to find celestial objects -- which lent the comet its name.
"Current models are showing the comet will likely peak between 3.5 and 4.5 magnitudes when it is nearest to Earth on October 21, which is dimmer than what they showed last week," Saint Louis Science Center wrote in an October update. "This is still bright enough that it could become naked-eye visible from light-polluted locations."
A Ukrainian amateur astronomer named Vladimir Bezugly discovered the SWAN comet on Sept. 11 while he was looking through images captured by SWAN, a science instrument called Solar Wind ANisotropies, which is installed on the Solar and Heliospheric Observatory in space.
"It was an easy comet for detection due to sufficient brightness in the (ultraviolet) band and location in the SWAN images, exactly in its center," Bezugly told Universe Today. He also noted it's the 20th official SWAN comet so far.
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