If you’re hoping to catch a glimpse of two comets, this week is your chance! After a year without any bright comets, two are showing up now: Comet C/2025 A6 (Lemmon) and Comet C/2025 R2 (SWAN).
On Tuesday, October 21, Comet Lemmon will be at its closest point to Earth, shining its brightest. It has reached a brightness of magnitude 4.5, similar to the Beehive Cluster and just a bit dimmer than the Andromeda galaxy. While you might see Comet Lemmon with the naked eye in very dark areas, binoculars will help you see it much better.
Comet SWAN will be nearest to Earth a day earlier, on Monday, October 20. But it’s dimmer, with a magnitude of 5.9. In astronomy, a higher magnitude means a dimmer object, so binoculars will be handy for this one too.
The best time to observe both comets this week will be around an hour and a half after sunset. On Monday, look for Comet Lemmon in the northwest sky, near the Big Dipper and the bright star Arcturus. If you follow the stars in the handle of the Big Dipper, you’ll find it about two-thirds of the way to Arcturus. On Tuesday, it will appear a bit higher in the sky.
To spot Comet SWAN, focus on the Summer Triangle—formed by the stars Vega, Deneb, and Altair—in the southwest sky. You’ll find Comet SWAN roughly halfway between Altair and the horizon.
Both comets are on very different paths. Comet Lemmon travels in a loop around the sun every 1,350 years and will reach 56 million miles from Earth during this visit. Interestingly, a gravitational pull from Jupiter altered its orbit, shortening its return time by nearly 200 years! It won’t be back until 3179.
On the other hand, Comet SWAN takes around 20,000 years to complete one orbit. During its closest approach, it will be about 24 million miles from Earth. That’s roughly one-quarter of the distance between Earth and the sun!
Now is a great time to check out some sky maps or finder charts to help locate these comets. Websites like The Sky Live, In-The-Sky, and Stellarium have helpful resources. If you’re eager to capture photos of these celestial visitors, there are guides available to help with that too.
Enjoy this rare cosmic event while it lasts! It’s a reminder of the beauty and mystery of our universe.
