Overview
- Comet Lemmon (C/2025 A6) is now visible before sunrise near the Big Dipper and is beginning to appear low in the northwest after sunset, while Comet SWAN (C/2025 R2) sits low in the southwest about 90 minutes after sunset.
- Observers report Lemmon around magnitude +5 to +5.7 and SWAN near +6, making binoculars or small telescopes the practical tools for spotting their green-tinged comae.
- Closest approaches are expected around Oct. 20–21, with SWAN passing about 24 million miles from Earth and Lemmon about 55 million miles, coinciding with a new moon and the Orionid meteor shower for darker skies.
- Lemmon was discovered Jan. 3 by the Mount Lemmon Survey in Arizona, while SWAN was identified in early September by an amateur using SOHO’s SWAN instrument data.
- Both long-period comets likely originate in the Oort Cloud and attract scientific interest, though forecasts note typical uncertainties in comet brightness and some inconsistent period estimates for SWAN.