New Comet SWAN (C/2025 R2) Pops Out from Behind the Sun

By: Bob King September 12, 2025 2

Comet SWAN25B — Newly discovered Comet C/2025 R2 (SWAN) is a bright object with a bluish-green coma and striking tail. This photo is from September 12th.
*E. Guido, M. Rocchetto, J. Ferguson*, *Spaceflux*

Congratulations to amateur astronomer Vladimir Bezugly of Ukraine! He discovered a bright new comet on September 11th around 1:45 UT in publicly posted images from the Solar Wind Anisotropies (SWAN) instrument on the orbiting Solar and Heliospheric Observatory (SOHO). This took a keen eye as the comet was barely visible just outside SWAN's solar occulting disk. It turns out that SWAN25B — its temporarily name — has hovered in virtually the same position for more than a month because its velocity and direction have nearly matched that of the Sun, maintaining a constant tight elongation. On September 15th it received the permanent designation C/2025 R2 (SWAN).

Comet SWAN25B at dusk — The comet is fortuitously placed right next to Mars and Spica for the next few evenings, but it will be lost in the twilight glow for northern mid-latitude observers. A preliminary orbit indicates that perihelion occurred on September 12th. To plot your own hourly positions of the comet, go to The Possible Comet Confirmation Page (PCCP) and select SWAN25B, then click *Generate Ephemeris*.
*Stellarium*

The object was quickly confirmed by Michael Mattiazzo of Australia, who spotted it in 15 x 70 binoculars on September 12.4 UT and estimated its magnitude at 7.3 with a tail in excess of 2°. Comet SWAN is currently located just a few degrees from Mars and Spica very low in the western sky after sunset and moving southeast. For Northern Hemisphere observers it's extremely low or lost in the solar glare for the time being. Those in the Southern Hemisphere have much better prospects, with the comet visible low in the west an hour or more after sunset.

Preliminary map for Comet SWAN25B — Although the comet slogs through twilight for the remainder of September, it picks up speed, elevation and elongation from the Sun as it trucks to the southeast. By the end of September and into October it should become more accessible to northern mid-latitude observers. This path is based on preliminary orbital elements from Sam Deen.
*MegaStar, courtesy of Emil Bonanno*

Viewing prospects for northerners will gradually improve from late September into October as the object slowly gains altitude and increasing elongation from the Sun — assuming the comet's current brightness isn't the result of a temporary outburst. Although its orbit is still preliminary, it appears it will pass 0.25 a.u. from Earth in October, according to comet observer Sam Deen. He also suggests the possibility that Earth will cross the newcomer's debris stream around October 4-6, with a possibility for a meteor shower.

Comet SWAN25B on Sept. 12, 2025 — Comet C/2025 R2 (SWAN) displays a coma 3.7 arc minutes across and 2.8-degree-long tail pointing southeast in this image made with a 135mm telephoto lens on September 12th.
*Martin Mašek*

Watch for the knot of material moving down the comet's tail in this animation made on September 12th. Amrum Astronomer

What's curious about this comet is that it wasn't discovered earlier. Granted, it was swamped by solar glare from Northern Hemisphere locations, but it's been in the evening sky for some time for Southern Hemisphere observers. One possibility is that C/2025 R2 only recently underwent a bright outburst that caused its magnitude to skyrocket. There's possible evidence for this. Based on the most recent images from September 13th, the coma has a peculiar, vaguely triangular shape (see images below) — sometimes called a "hammerhead" — which may indicate that the nucleus is undergoing fragmentation.

Comet SWAN25B with odd coma — Comet C/2025 R2 displays an unusual triangular coma in this photo made on September 13th. It may be a sign that the nucleus is either shedding pieces or breaking apart. Outgassing from multiple fragments cause the coma's normally symmetrical shape to look out of round.
*Jost Jahn / Deep Random Survey*

Comet SWAN25 odd coma — The coma has an odd appearance in this image from September 12th. Details: Stack of 27 30-second exposures with a QHY 268M CMOS camera.
*Roger Hellot*

Comet SWAN25 from Mexico Sept. 13, 2025 — Spica (upper) left and Mars join the scene with the comet on September 13th from Zacatecas, Mexico. Details: 300mm lens, ISO 3200, 20 x 3 second exposures
*Da Ko*

Comet SWAN25B from Australia — Rob Kaufman's photo, taken from Bright, Victoria, Australia on September 12th with a 200mm telephoto lens, gives a better idea of how the comet looks in binoculars with a bright, condensed coma and faint tail. Kaufman described the coma as "very green." North is up.
*Rob Kaufman*

We'll have more on the comet in the next days, so please check back. In the meantime, you can learn more about what the comet is doing right now in the online discussion group comets-ml.

About Bob King

I love the sky (day and night) and have been a skywatcher and amateur astronomer since childhood. I'm also a long-time member of the American Association of Variable Star Observers (AAVSO) and Astronomical League. I pen the Astro Bob blog and have written four books: Night Sky with the Naked Eye (2016); Wonders of the Night Sky You Must See Before You Die (2018) and Urban Legends from Space (2019) and Magnificent Aurora, published in 2024. The universe invites us on an adventure every single night. To accept the invitation, we only need look up.