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Color changes for the Surface of 6478 Gault

Presentation #514.07 in the session “Hints of Cometary Activity”.

Published onOct 26, 2020
Color changes for the Surface of 6478 Gault

(6478) Gault is a main belt asteroid in the Phocaea Family which was discovered to have activity in January 2019, and precovery images reveal it has been consistently active since at least September 2013. Because Gault’s activity is not correlated with heliocentric distance, it is believed to be caused by it being a fast rotator near the asteroid break-up limit of ~2.2 hrs. We present new data and have collected images and photometry from several telescopes dating back several apparitions. We found that after January 2019 Gault became active again on 2019 July 3 with deep stacked images revealing two newly formed tails. A surface brightness analysis of images taken on 2020 July 1 reveals that Gault was again slightly active with a small dust production between 10-3–10-4 kg/s. Using early archival data we attempted to find a rotation period but were unable to due to dust from activity masking nucleus rotational variation. Between February and August 2019 Gault showed significant color variations. The spectral reflectivity slope varied between 4.16 ± 0.9 %/100nm and 14.37 ± 0.7 %/100nm. The colors are consistent with three asteroid taxonomic classes: S-types, C-types and D-types. These color variations imply that Gault’s activity is either revealing new fresh material unaffected by long-term space weathering, or material of different mineralogies has been delivered to Gault’s surface through exogenic processes. These results are notable since color variations this significant on an asteroid surfaces have not been observed from the ground before.

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