Home=Current Comets: C/2025 F2
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On images taken by the SWAN camera (on board of the SOHO spacecraft) between Mar. 22 and 31, 2025, Vladimir Bezugly, Michael Mattiazzo and R.D. Matson independently detected a comet that they estimated to be of about magnitude 11. They published this discovery in the Comet's Mailing List, whereupon numerous observers tried to confirm the potential comet. Michael Jäger, Gerald Rhemann and E. Prosperi succeeded in photographing the comet in the constellation Pegasus (at 2° distance from the position determined by SWAN images) on Apr. 3. The comet appeared as an object of magnitude 10.0, showing a 3.5' coma and a 10' tail in p.a. 283°. An image taken by K. Yoshimoto a few hours later showed a 35' tail in p.a. 295°. The first visual sighting was made by Maik Meyer on the morning of Apr. 4: he estimated a total brightness of 9.2 mag of the strongly condensed 2' coma. Around Apr. 5 an outburst of about 1 mag occurred. On Apr. 8 the comet was of magnitude 7.5, showing a coma of about 4' diameter. It was not until Apr. 8 when CBET 5538 announced the discovery of the comet, designating it C/2025 F2 (SWAN). The comet will pass perihelion at the solar distance of 0.33 AU on May 1. Its maximum brightness can only be very roughly predicted. Based on the published brightness estimates it could reach 3-4 mag. It should be brighter than 16 mag until the end of September. During this period its orbit - which is perpendicular to the ecliptic - takes it through the constellations Pegasus, Andromeda, Triangulum, Aries, Taurus, Orion, Lepus, Columba, Puppis, Vela into Volans. From mid-European locations it can be seen just above the northeastern morning horizon until the last week of April and then very low above the evening northwestern horizon until the first days of May. However, it will be a difficult object in twilight. There is a certain possibility that the comet will disintegrate on its way towards the Sun.
Total Brightness and Coma Diameter
Brightness Variations (based on the brightness parameters m0=10.0 mag / n=3)
Actually the comet disintegrated on its way towards perihelion, as 85 observations by 30 observers document. As a result of the outburst on Apr. 5 the maximum brightness of 7.5 mag was already reached on Apr. 7 (it was just of magnitude 12 on Mar. 30). Between Mar. 30 and Apr. 7 the coma diameter increased from about 1.5' (approx. 100,000 km) to the maximum of 4' (250,000 km). Thereafter brightness and coma diameter decreased and the coma became more and more elongated, while loosing its central condensation. On Apr. 27 the comet had faded to 9.5 mag and the coma diameter had decreased to 1.7' (85,000 km). The degree of condensation increased until Apr. 7 from DC 3-4 to DC 7, only to decrease to DC 2-3 by Apr. 27. A tail could be detected throughout the whole apparition. On CCD images it reached a maximum length of 1.2° (6 mio. km) also on Apr. 7. Its direction changed from WNW to North during the short apparition. During the last days of April the comet could only be documented photographically under difficult circumstances. It appeared as an elongated, very diffuse cloud of uniform surface brightness without any central concentration.Andreas Kammerer
