Home=Current Comets: C/2025 R3
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On Sep. 8, 2025, the PANSTARRS team discovered an additional comet, this time in the constellation Andromeda. Comet C/2025 R3 (PANSTARRS) showed a condensed 5" coma of total magnitude 19.5 and a broad 10" tail in p.a. 165-225°. The comet will pass perihelion at a solar distance of 0.50 AU on Apr. 19, 2026, expected to peak at 9 mag if it shows an average development (CBET 5607). It is expected to be brighter than 16 mag between February and June 2026. During this period it will move through the constellations Pegasus, Pisces (perihelion), Cetus, Taurus, Eridanus, Orion, Monoceros, and Canis Major. From Central European locations the comet can only be observed in the evening sky until mid-February 2026 and just above the eastern horizon in the morning sky between early March and mid-April. However, the absolute magnitude, as derived from published observations, is 2 mag below the Bortle-limit. Thus there is a certain probability that the comet will disintegrate on its way to the Sun. If the comet survives its perihelion without major damage, J. Marcus' formulae predict that there will be significant forward scattering in the second half of April, which could increase its brightness by up to 6.5 mag on Apr. 26! However, the comet will only be 5° from the Sun on that day. Earth will cross the comet's orbital plane on Apr. 29.
At the start of February 2006 the comet's development is still extremely uncertain. The few observations published so far indicate an absolute magnitude 2 mag higher than previously assumed. Nevertheless, the absolute brightness remains below the Bortle limit, albeit only just. Thus, the probability that the comet will disintegrate on its way toward the Sun or shortly after perihelion is quite high. The published observations indicate magnitudes of about 13.5 for early February 2026. Thus the resulting brightness parameters are very roughly
m0 = 10.0 mag / n = 3.
Applying these parameters the comet should be of magnitude about 7.5 at perihelion, 6.5 mag on Apr. 26, and 9.0 mag in mid-May. In combination with the forward scattering the comet could thus reach a maximum brightness of roughly 0 mag on Apr. 26! But only if it survives the perihelion passage unscathed. On the day of maximum forward scattering, however, the comet rises after the Sun in the morning and sets before the Sun in the evening for locations in Central Europe.
Update on Mar. 27, 2026:
So far the comet develops very steadily and extremely favorably. Based on 52 observations by 24 observers (until Mar. 25, 2026), its brightness development can be very well described by the parameters
Thus the comet could peak at 2.5 mag on Apr. 24. Taking into account the forward scattering of up to 6.5 mag on Apr. 25, the comet could become brighter than 0 mag between Apr. 22 and 28, reaching -4 mag on Apr. 25. However, there remains a certain probability that the comet will disintegrate on its way to perihelion.
Total Brightness and Coma Diameter
At the end of March, the significantly condensed (DC 6) coma reached a diameter of just under 6' (400,000 km).If the comet will reach perihelion it will exhibit an interesting tail morphology for several days, as shown in the following diagram.
Simulation of the Tail Development
Andreas Kammerer
