Home=Current Comets: 13P (2024)
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On Aug. 24, 2023, Alan Hale rediscovered comet 13P/Olbers (P=69.25a) remotely with the 1.0m Schmidt-Cassegrain telescope at Las Cumbres Observatory. The stellar comet was located in the constellation Eridanus and had a magnitude of about 21.5 mag. The comet was observed during its last perihelion passage in 1956. The next perihelion passage at the solar distance of 1.18 AU will take place on June 30, 2024 with an expected maximum brightness of 7.5 mag (CBET 5289). At this time my empirical formulae predict a maximum coma diameter of 5-6' and a maximum visual tail length of just under 0.5°. It should be brighter than 16m between December 2023 and August 2025. During this period it will move through the constellations Eridanus, Cetus, Taurus, Auriga, Lynx (perihelion), Leo Minor, Ursa Major, Coma Berenice, Bootes, Virgo, Libra, Ophiuchus and Sagittarius. Observing from Central European locations it will be an object visible during the whole night in the first few weeks, but will change to the evening sky in January 2024. In February 2024 it will reach its maximum altitude of 35° before starting to sink towards the horizon. In the most interesting weeks (May to September 2024) it will unfortunately experience altitudes of less than 20° (in May even less than 10°). At the end of October 2024 it will disappear above the western evening horizon. From February to mid-June 2025 it will reappear in the morning sky, but the altitudes will be less than 15°. On June 17, 2024 and on Dec. 17, 2024 the Earth will cross the comet's orbital plane.
Despite the rather moderate observational circumstances worldwide so far, 145 observations from 41 observers can already be used for an analysis at the beginning of May 2024. These show a brightness development that can be well represented with the parameters
m0 = 3.4 mag / n = 8.5.Between the beginning of January and the beginning of May 2024 the comet brightened from 14 mag to 8.5 mag. If the comet should continue to develop in this manner until perihelion it would reach a maximum brightness of 6.3 mag at the beginning of July 2024.
Total Brightness and Coma DiameterThe coma diameter increased from just less than 1' (85,000 km) to 3.5' (375,000 km) during the apparition. The coma appears noticeably condensed (with the degree of condensation constant at DC 4-5). Tail sightings are the exception so far, not at least due to the poor observational circumstances.
Andreas Kammerer