Presentation #110.06 in the session “Active Asteroids & Weakly Active Comets”.
Comet 289P/Blanpain was discovered in 1819, but was lost soon after its initial observation . However, the discovery and further observations of asteroidal object 2003 WY25 showed that this object is actually in fact the comet 289P, or at least a fragment of it . Comet 289P is an established example of cometary fragmentation, and passed within 0.09 AU from the Earth in January 2020, providing an excellent opportunity for detailed study. Sixty-four 30 second exposure time, fifty-six 15 second exposure time, and three 751 second exposure time images were taken over 8 orbits with the F350LP filter using WFC3 on the Hubble Space Telescope within ~3 months from 289P’s perihelion in order to constrain the current state of the comet, look for fragments, and gauge its activity levels. We analyzed the Hubble images in order to determine how large and active the comet’s nucleus is. Initial analysis showed that the comet was extremely weakly active at the times of the observations, with Afrho ≪ 1 cm, which is a much smaller Afrho compared to some classically weak comets such as comet P/2016 BA14 with a Afrho of 0.19 ± 0.01cm  and and comet 209P/LINEAR with a Afrho near 1 cm . We will present our estimation on the nucleus’ size and its activity levels, as well as the upper limit of fragment sizes in the nucleus’ vicinity. We will also discuss the implications our finding has on previous conclusions made on 289P’s behavioral and physical history.
This research is supported by NASA through grant HST-GO-15978 from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.
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