C/2025 R2 (SWAN)
Long-period comet discovered via SOHO's SWAN instrument in September 2025.
C/2025 R2 (SWAN), formerly known as SWAN25B, is a long-period comet discovered on 11 September 2025 by amateur astronomer Vladimir Bezugly through SWAN imagery on the Solar and Heliospheric Observatory (SOHO). It peaked around apparent magnitude +6 in late September 2025 and is notable as the 20th comet discovered through SOHO's SWAN instrument.
Quick Facts
- Discoverer
- SOHO–SWAN / Vladimir Bezugly
- Discovery Ref
- CBET_5606 · MPEC_2025-R102
- Discovery Date
- 11 September 2025
- Designations
- SWAN25B, CK25R020MPEC_2025-R102
- Orbit Ref
- jpldata
- Epoch
- 11 November 2025 / (JD 2460990.5)
- Earliest Precovery Date
- 13 August 2025
- Obs
- 2225
- Semimajor
- 89 AU (inbound)barycenter / 84 AU (outbound)
- Period
- ≈840 years (inbound)barycenter / ≈770 years (outbound) / 810 yearsjpldata · MPC (near perihelion)
- Eccentricity
- 0.9943 (inbound)barycenter / 0.9940 (outbound)
Facts from the source article.
Lore & Background
The comet was first spotted in SWAN images on 11 September 2025 by Vladimir Bezugly, with an estimated magnitude of 7.4 and a tail about 2 degrees long. It was located in the constellation Virgo and better seen from the southern hemisphere. The comet was not discovered earlier due to the Holetschek effect, being less than 30 degrees from the Sun between August 7 and September 13. It rapidly brightened from magnitude 11 to 8 between August and September, reaching magnitude 6.2 on 16 September. An outburst later in September brought it to magnitude 5.9. On 2 October it passed near Zubenelgenubi, and on 17 October it passed directly over Messier 16. On 2 November 2025, a possible fragmentation event was observed from the Two-meter Twin Telescope at Teide Observatory, with reports of the nucleus splitting or releasing a substantial fragment, likely occurring around mid-October. NASA announced in December 2025 that the PUNCH spacecraft observed the comet between 25 August and 2 October 2025.
Reader's Guide
C/2025 R2 (SWAN) is significant as the 20th comet discovered through SOHO's SWAN instrument, highlighting the role of amateur astronomers in comet detection. Its discovery was delayed by the Holetschek effect, and it was probably inactive at opposition in February 2025. The comet underwent an outburst and a possible fragmentation event observed in November 2025. Spectra taken on 18 October 2025 at the University Observatory Jena showed prominent emission features of C2, NH2, and [OI], but no sodium emission, contrasting with C/2025 A6 (Lemmon). The comet's orbit is dynamically old, with an inbound period of about 840 years and outbound of about 770 years. Earth passed near its meteoroid stream around 6 October 2025, but the large Earth-MOID of 0.048 AU and long orbital period made a meteor shower unlikely.
Did You Know?
- C/2025 R2 (SWAN) was discovered by amateur astronomer Vladimir Bezugly through SWAN imagery on SOHO.
- The comet underwent a possible fragmentation event observed on 2 November 2025 at Teide Observatory.
- The comet's inbound orbital period was about 840 years, and outbound about 770 years.
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