Last chance: Rare green comets visible tonight before 1,150-year disappearance

Sky watchers have a final opportunity this Friday, October 24, to witness two rare green comets before they vanish from sight for over a millennium.

The comets identified as Lemmon (C/2025 A6) and SWAN (C/2025 R2) are visible for those in the Northern Hemisphere with binoculars.

But the chance to view them will vanish soon as they recede from Earth.

According to Jamie Cartier, a senior science reporter, “This is the best remaining night to see them,” as there will be a full moon soon which will make the comets much harder to spot.

The comets are not only a temporary slight but a truly historic one. Comet Lemmon was last in the inner solar system in the year 875 and is not expected to return until around 3175, a 1,150 year journey.

Its companion, Comet SWAN, is on an even more epic voyage, with an orbital period of roughly 20,000 years.

How to see them

The optimal time frame of observation is brief beginning approximately around 90 smoking minutes following the sunset and lasts approximately 30 minutes. The two comets will be in contrary directions:

• Comet Lemmon: To the westward of the bright star, Arcturus. The brighter is the one and it is heading towards the west of the Big Dipper.
• Comet SWAN: In the southwest, the three bright stars of the Summer Triangle.
• They can be viewed by the naked eye as small, vague spots in a very dark place, however, to see them it is better to use a pair of binoculars (8x42 or 10x50 are suggested). There are accurate guides in the form of stargazing apps such as Stellarium or SkySafari.

In New York City, the sunset occurs at 5:59 p.m. EDT hence the best time to observe comets would be between 7:29 and 7:59 p.m. EDT.