Gather ’round for this galactic double feature.
After a year devoid of comets visible to the naked eye, two of the celestial entities — C/2025 A4 (Lemmon) and C/2025 R2 (SWAN) — will be gracing our skies at around the same time.
Lemmon will reach its closest point to Earth on Tuesday, October 21st, wherein will come within about 56 million miles from Earth, according to Livescience.
Meanwhile, its compatriot Comet SWAN (C/2025 R2), known for its brilliant bluish-green hue, will pass even closer, at roughly 24 million miles. Both are expected to be at their brightest between Oct. 20 and Oct. 21 respectively with Lemmon clocking in at three times as luminous as its fellow interstellar iceball.
How to see the green comet
That’s why, despite SWAN’s closer proximity, stargazers will need binoculars to catch its fly-by while Lemmon will be visible to the naked eye in very dark skies.
When to see comet Lemmon
The latter, which was was discovered in January 2025 and has been steadily brightening during its journey through the solar system, will be most visible an hour and a half after sunset on Tuesday, October 21.
It will appearing the northwest sky, near the Big Dipper and the bright star Arcturus, and close to the horizon.
Meanwhile, comet C/2025 R2 (SWAN), which was was discovered in September 2025 by the Solar and Heliospheric Observatory’s SWAN instrument, will be at its clearest at around the same time but a day earlier.
Skywatchers should look for the Summer Triangle of bright stars — Vega, Deneb and Altair — in the southwest. SWAN will be situated between Altair and the horizon.
Dion’t worry if you can’t catch these heavenly hailstones live, however.
Astronomer Gianluca Masi and his Virtual Telescope Project will host a special livestream on Oct. 20 beginning at 1:30pm so people can catch this cosmic double-header remotely.
“So far, living in the Northern hemisphere, I could admire C/2025 A6 Lemmon only, but C/2025 R2 SWAN is quickly joining the show and we are ready to amaze every astronomy lover with our live feed!” Masi told Space.com in an email.
We advise watching them in some capacity as Lemmon won’t be making a visible comeback tour again until the year 3175, making this a once-in-a-lifetime event.