As attention turned towards incoming interstellar comet 3I/ATLAS, the cosmos delivered another surprise: C/2025 R2 (SWAN), temporarily known as SWAN25B. This new comet avoided detection and suddenly burst onto the scene unexpectedly as it emerged from the Sun's glare, sparking excitement among astronomers and skywatchers alike.
C/2025 R2 (SWAN) is a long-period comet discovered on September 11, 2025, by amateur astronomer Vladimir Bezugly, who first spotted it in images from the SWAN instrument onboard the Solar and Heliospheric Observatory spacecraft. Soon thereafter, multiple observers independently confirmed the comet's visibility.
What is Known
- The comet's closest approach to the Sun occurred on September 12, 2025, at about 0.5 AU or 75 million kilometers (46.6 million miles).
- The comet is currently best seen in the Southern Hemisphere but is gradually moving northward.
- The comet's closest approach to Earth occurs on October 19, 2025, at 0.26 AU or roughly 39 million kilometers (24 million miles).
- Based on preliminary trajectory estimates, the comet should cross the celestial equator around November 3, 2025, improving its visibility for observers in the Northern Hemisphere.
- The comet’s orbital period and aphelion (furthest point from the Sun) are uncertain. Estimates range from 1,000 to 2,000 years.
Visibility Tips
- As of early October 2025, Comet C/2025 R2 (SWAN) is in the constellation Libra and will cross into Scorpius around October 10. Look low in the western sky during evening twilight, ideally with a clear, unobstructed horizon.
- The comet is shining around magnitude +5.9. Observers using binoculars or a telescope should have little trouble finding it under dark skies. With good conditions, especially in long-exposure images, the comet reveals a greenish coma and a tail extending 2.5° or longer—about the length of five Full Moons across the sky!
- Astronomers have speculated that Earth might cross the comet’s orbital path on October 5, 2025. If Earth encounters cometary debris, observers may see enhanced meteor activity around that date.
- On October 17, 2025, C/2025 R2 (SWAN) will pass just south of the Eagle Nebula (Messier 16), creating an excellent opportunity for astroimagers and visual observers.
- The comet's brightness should peak around magnitude +4 on its closest approach to Earth on October 21, 2025. That should be bright enough to see with the naked eye from a dark sky site (fingers crossed!).
- If you own a Celestron telescope, make sure to download your SkyPortal Powered by SkySafari™ Mobile App to determine the comet’s latest magnitude estimates and finder charts. The comet should become easily visible in binoculars or telescopes as the sky darkens. However, light pollution, horizon obstructions, and even moonlight affect whether you can see the comet.
Comet C/2025 R2 (SWAN) may not rival history’s great comets such as West or Hale-Bopp, but it offers a rare chance to witness a new visitor to the inner solar system. Unpredictable as always, it could brighten or fade without warning, which comes with the thrill of comet-watching. With its closest approach in mid-October and a photogenic pass near the Eagle Nebula, comet SWAN may be a rewarding target for observers and astroimagers. Keep your Celestron binoculars and telescopes handy, follow the latest reports, and be sure to step outside this October to catch the show. Clear skies and happy comet observing!