289P/Blanpain
289P/Blanpain, formerly D/1819 W1 is a short-period comet with an orbital period of 5.2 years. It was discovered by Jean-Jacques Blanpain on November 28, 1819 but was considered lost until it was recovered in 2013. It was last observed in 2020.
Observational history
The comet was discovered by Jean-Jacques Blanpain on November 28, 1819. Blanpain described the comet as having a "very small and confused nucleus". Another independent discovery was made on December 5 of that year by J. L. Pons. Following this the comet was lost, and was given the designation 'D'.However, in 2003, the orbital elements of newly discovered asteroid were calculated by Marco Micheli and others to be a probable match for the lost comet. On 12 December 2003, it approached Earth at a distance of. Further observations of the asteroid in 2005 by David C. Jewitt using the University of Hawaii 2.2 m telescope on Mauna Kea, appeared to reveal a faint coma, which supports the theory that is the lost comet, or a part of it. The comet was officially established as periodic comet 289P in July 2013, after being rediscovered by the Pan-STARRS survey during an outburst event.
The comet underwent a major outburst in July 2013, when it brightened by 9 magnitudes, one of the largest observed comet outbursts. The comet was first spotted in images obtained by Pan-STARRS on 4 July 2013, having a reported magnitude of about 20, and brightened to a magnitude of about 17.5 and featured a coma about 30 arcseconds across and a broad tail. It is estimated that the comet lost about 108 kg of dust, which corresponds to about 1% of the comet's mass. The comet then was located 3.9 AU from the Sun.
289P was better viewed near and after the 2019-Dec-20 perihelion passage. On 11 January 2020 the comet approached Earth at a distance of. The next close approach will take place on 6 November 2035, at a distance of.
Scientific results
The observations of the comet by the University of Hawaii 2.2 m telescope indicate the nucleus of the comet is quite small. Assuming an albedo of 0.04, which is the mean value for short period comets, its radius is about, although the presence of coma and unknown phase function means that there is quite some uncertainty. However at that time it was the smallest known cometary nucleus. Observations of the comet in 2019–20 by NEOWISE indicate a rotational period of 8.8536 ± 0.3860 hours or 15.6 hours, with the former being more likely.The ejected dust masses are 4100 ± 200 kg inbound and 1700 ± 200 kg outbound, respectively, based on the observations by NEOWISE. The dust production rates are Qdust = 0.01–0.02 kg per second, corresponding to a dust-to-gas production ratio of 2 ≤ fdg ≤ 6. The resulting fractional active area, fA = 3.8 ± 1.9 × 10−5, is the smallest yet reported. The absence of 4.6 μm excess suggests that 289P/Blanpain contains negligible amounts of and CO. The perihelion-normalized nongravitational acceleration, a'NG = 3.1 × 10−6, is approximately an order of magnitude smaller than the trend observed for well-studied comets, consistent with weak outgassing.