Double comet alert! Comets Lemmon and SWAN will be closest and brightest this week. Here’s how to spot them.

If you want to see two comets, your best chance will be early in the week. After a year without a comet bright enough to be seen without specialized equipment, two – comet C/2025 A6 (Lemmon) and comet C/2025 R2 (SWAN) – appeared at the same time.

Comet Lemmon might look more like a lime than its name suggestsBut on Tuesday (October 21), the dusty snowball from the outer solar system will reach its closest point to Earth and will most likely shine at its brightest. It has now reached a magnitude of 4.5, according to SpaceWeather.com — about the same luminosity as the Spring Beehive Cluster (M44) and only a little fainter than the Andromeda Galaxy (M31).

Although Comet Lemmon is technically visible to the naked eye in very dark skies, you will need binoculars to see another icy, fainter visitor, the comet C/2025 R2 (SWAN). Remarkably, Comet SWAN will approach Earth on Monday (October 20), the day before Comet Lemmon, but it will be about three times fainter, at magnitude 5.9. (In astronomy, the higher the magnitude, the darker the object.)

The best time to see both comets this week will be about an hour and a half after sunset; you can check local times at Timeanddate.com. On Monday, Comet Lemmon will be visible in the northwest sky, near the Big Dipper and the bright star Arcturus, and near the horizon.

Follow the shape of the stars in the handle of the Big Dipper to “arc to Arcturus”; the comet will be about two-thirds of the way there. On Tuesday it will be a little higher. For comet SWAN, look for the summer triangle of bright stars – Vega, Deneb and Altair – in the southwest. You will find comet SWAN halfway between Altaïr and the horizon.

Useful search charts and star charts for both comets are available at The sky live, In-The-Sky.org And Stellariumas well as in night sky apps such as Sky Guide, Sky Tonight and SkySafari 7 Pro. If you want to try photographing comets, our guide has what you need.

The two comets follow very different journeys. Comet Lemmon will reach 56 million miles (89 million kilometers) from Earth on Tuesday, according to The sky liveen route to loop around the sun on November 8 during its 1,350-year orbit around the sun. (However, Jupiter sapped some of Comet Lemmon’s orbital energy, shortening its period by almost 200 years, according to Star Walkhe will therefore not return before 3179.)

Comet SWAN is a long-period comet, orbiting the sun every 20,000 years, according to The universe todayand on Monday it will be 24 million miles (39 million kilometers) away when it leaves the inner solar system. This is about a quarter of the distance between Earth and the Sun.