A pair of once-in-a-lifetime comets will rocket through our skies this October, 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 from our perspective.
You can spot these green gaseous globes and their streaming tails right now, but they’ll be even easier to see this coming week. SWAN will shine the brightest around Monday, Oct. 20, NBC News reports.
Just a day later, on Tuesday, Oct. 21, Lemmon will make its peak showing in the dark sky. 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.
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«Current models are showing the [Lemmon] 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 update. «This is still bright enough that it could become naked-eye visible from light-polluted locations.»
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.
How to see Lemmon and SWAN this month
The darker the night sky, the easier it will be to see comets, moons, planets and stars. If you live in a city, bundle up and take an evening skygazing trip to the country, where there’s less light pollution. Oh, and grab blankets, chairs and something warm to drink.
It takes your eyes a while to adjust to the darkness. Find a comfortable spot where you can stay still and gaze up. The comets might be bright enough to see without aid, but NASA recommends binoculars as a great entry-level stargazing tool.
Telescopes are one of the best ways to skygaze, and you might be able to find one to use or rent at your local library or university. But modern telescopes can also be fairly affordable.
Smartphone apps can also be helpful when trying to identify celestial phenomena and where to find them. For a few recommendations, check out our list of stargazing apps.
A sky full of wonders
Aside from the newly discovered comets, skywatchers have a few other cosmic treats to enjoy this month.
The Orionids meteor shower, when Earth travels through the massive tail of Halley’s Comet, began earlier this month, but you’ll be able to see the meteors through the beginning of November.
The next supermoon, known as the Beaver Moon, will take place on Nov. 5.
