Sky watchers have a final opportunity on Friday, October 24, to witness two rare green comets before they vanish from sight for over a millennium.
The comets, named Lemmon (C/2025 A6) and SWAN (C/2025 R2), are visible to those in the Northern Hemisphere with binoculars. However, this opportunity will be fleeting, as the comets will soon recede from Earth and be gone for centuries.
Jamie Cartier, a senior science reporter, emphasized that “this is the best remaining night to see them,” noting that the upcoming full moon will make spotting the comets much harder.
Comet Lemmon, which was last in the inner solar system in 875, is not expected to return until around 3175, making its next appearance a 1,150-year wait. Its companion, Comet SWAN, is on an even longer orbital journey, with a period of approximately 20,000 years.
How to see them:
The best viewing time is brief, starting about 90 minutes after sunset and lasting for approximately 30 minutes. The two comets will be visible in different directions:
Comet Lemmon: To the west of the bright star Arcturus, it will be brighter and heading towards the west of the Big Dipper.
Comet SWAN: To the southwest, near the three bright stars of the Summer Triangle.
While they can be seen with the naked eye as small, faint spots in very dark areas, binoculars (8×42 or 10×50 are recommended) will provide a better view. Stargazing apps like Stellarium or SkySafari can offer precise guides for locating the comets.
In New York City, with sunset at 5:59 p.m. EDT, the best time to observe the comets will be between 7:29 and 7:59 p.m. EDT.
