Two Greenish Comets Captivate Night Skies This October
This October brings a rare celestial treat: two greenish comets streaking across the night sky. C/2025 A6 (Lemmon) and C/2025 R2 (SWAN) are gracing the inner solar system and are visible from the Northern Hemisphere through the end of the month. For amateur stargazers, this is a chance to witness two icy wanderers in a single season, weather permitting.
What Makes These Comets Green
The faint green hue seen in these comets comes from the presence of carbon-bearing gases released as they melt near the Sun. As the nuclei warm, jets of gas and dust form a glowing coma and tails that can stretch across the sky. The emerald color is a reminder of the delicate chemistry at work as primordial material from the early solar system is exposed to sunlight.
Viewing Outlook: When and Where to Look
Both comets are accessible with binoculars or a small telescope, though visibility depends on your local weather and light pollution. Here are practical tips to maximize your chances:
- Comet Lemmon (C/2025 A6): In the Northern Hemisphere, it will appear near the Big Dipper before dawn in the coming days. Look northeast, slightly below the bowl and handle, in the hours before sunrise. In about a week, Lemmon shifts to the evening sky and rises in the west, making it potentially observable with the naked eye around Oct. 21 when it is closest to Earth.
- Comet SWAN (C/2025 R2): Best seen about 90 minutes after sunset, in the southwest. Binoculars or a small telescope will be needed, as SWAN is unlikely to be bright enough for naked-eye viewing. The comet climbs higher on the horizon as the days pass and grows brighter approaching its close approach to Earth around Oct. 20.
If skies are exceptionally clear and dark, you might even glimpse both comets on the same night near the end of October. A little patience and a dark, low-light site will go a long way when chasing these two icy visitors.
A Quick Backstory on the Discoveries
Comet Lemmon was discovered in January by the Mount Lemmon Survey, which tracks near-Earth objects from the Santa Catalina Mountains in Arizona. Comet SWAN’s discovery traces back to early September, when an amateur astronomer noticed it in images from NASA’s Solar and Heliospheric Observatory (SOHO) using the SWAN instrument. SOHO has been a workhorse for solar studies since its launch in 1995, and its data continues to yield surprising celestial finds.
What to Expect Over the Coming Weeks
As both comets swing through the inner solar system, observers should monitor local astronomy clubs and skywatching sites for up-to-date advisories on timing and visibility. The brightness of comets can be unpredictable, influenced by how much volatile material they shed as they approach the Sun. In optimal conditions—clear skies, low light pollution, and steady atmospheric steadiness—this October could become memorable for devoted skywatchers who savor a double-feature of emerald comets.
Tips for Observing
- Give your eyes time to adjust; avoid looking at bright lights nearby.
- Use a stable mount or tripod for your binoculars or telescope.
- Check local dawn and dusk times, and scout a viewing spot with a clear northeastern and western horizon.
- Record your observations with dates and rough coordinates to compare notes with fellow observers.
Why This matters for stargazers
Seeing two greenish comets in one month is a rare celestial moment. It highlights the dynamic nature of the solar system and gives both seasoned enthusiasts and curious newcomers a tangible connection to the cosmos. If you miss them this October, keep an eye on late-year forecasts, as often comets offer second chances with improved viewing windows after perihelion.
