S. R. Chesley, W. M. Owen, Jr., E. W. Hayne, A. M. Sullivan, R. C. Dumas, J. D Giorgini, A. B. Chamberlin, S. P. Synnott, C. S. Vazquez (JPL)
We estimate the mass of the fourth largest asteroid, 10 Hygiea, to be 9.02±0.26 \times 1019 kg (GM = 6.02 ±0.17 km3/s2 or 0.454±0.013 \times 10-10\; GM\odot). While the least-squares estimate is consistent with values published elsewhere [1], the precision of our result is an order of magnitude finer than other results based on a single perturbed asteroid. This estimate relies wholly upon a close approach to asteroid 3946 Shor that took place 1998 Mar 29.90726 TDB at a distance of 0.014399 AU and relative velocity 0.914 km/s. Because of the substantial effect of that encounter, the mass estimate is insensitive to mass variations in other large Shor perturbers. The precision of the result was afforded by a series of high precision astrometric observations of Hygiea and Shor obtained at Table Mountain Observatory from 1996 through 2004. The IRAS-derived diameter of 407 ±7 km [2] leads to a bulk density estimate of 2.55±0.15 g/cm3.
[1] G. Michalak (2001) A&A 374, 703--711.
[2] E. Tedesco et al. (2002) AJ 123, 1056--1085.
Bulletin of the American Astronomical Society, 37 #2
© 2005. The American Astronomical Soceity.