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Masses, bulk densities, and macroporosities of asteroids (15) Eunomia, (29) Amphitrite, (52) Europa, and (445) Edna based on Gaia astrometry

Presentation #309.03 in the session “Main Belt Asteroids”.

Published onOct 03, 2021
Masses, bulk densities, and macroporosities of asteroids (15) Eunomia, (29) Amphitrite, (52) Europa, and (445) Edna based on Gaia astrometry

Gaia Data Release 2 (DR2) includes milliarcsecond-accuracy astrometry for 14,099 asteroids. One of the main expected scientific applications of this data is asteroid mass estimation via modeling perturbations during asteroid-asteroid encounters.

We apply our Markov-chain Monte Carlo algorithm to explore the practical impact of Gaia astrometry of asteroids for the purpose of asteroid mass and orbit estimation by estimating the masses individually for four large asteroids. We use combinations of Gaia and/or Earth-based astrometry so as to determine the impact of Gaia on the estimated masses. By utilizing published information on estimated volumes and meteorite analogues, we also derive estimates for bulk densities and macroporosities. In addition, we attempt to estimate a mass for (445) Edna with Gaia data alone based on its past close encounter with (1764) Cogshall.

We find that our mass estimation algorithm works well with a combination of Gaia DR2 and Earth-based astrometry and provides very impressive results with significantly reduced uncertainties in comparison to results with Earth-based astrometry alone. On the other hand, the study of (445) Edna reveals that mass estimation with DR2 astrometry alone is unfeasible and that it must be combined with astrometry from other sources to achieve meaningful results. We note that the DR2 has a caveat in that many asteroids interesting for mass-estimation purposes are not included in the relatively small sample. This limits the number of asteroids to which mass estimation can be applied. However, this issue will largely be corrected with the forthcoming third Gaia data release which is expected to allow for a wave of numerous accurate mass estimates for a wide range of asteroids.


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