A pair of once-in-a-lifetime comets are rocketing through our skies right now, and it's a rare treat because they won't be back for hundreds of years. The comets, C/2025 A6 (Lemmon) and C/2025 R2 (SWAN), look similar. Both comets have already had their brightest nights on Oct. 20 and Oct. 21. But if you're out and about this final week of October, you can still spot these green gaseous globes and their streaming tails.
You'll be able to see Lemmon without any equipment, but SWAN will be pretty faint, says Jason Steffen, assistant professor of physics and astronomy at UNLV.
Don't miss any of our unbiased tech content and lab-based reviews. Add CNET as a preferred Google source.
CNN reports that SWAN will next come by again in 650 to 700 years, and Lemmon won't return for another 1,300 years.
"Comet Lemmon is called a non-periodic comet. Unlike Halley's comet, which comes around every 76 years, a non-periodic comet's orbit is really highly elliptical," Steffen says. "The last time it was here was in the 700s."
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 predawn 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 gave the comet its name.
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.
... continue reading