Original Article

Celestial Mechanics and Dynamical Astronomy

, Volume 100, Issue 1, pp 27-42

First online:

Open Access This content is freely available online to anyone, anywhere at any time.

Astrometric masses of 21 asteroids, and an integrated asteroid ephemeris

  • James BaerAffiliated withSouth University Email author 
  • , Steven R. ChesleyAffiliated withJet Propulsion Laboratory


We apply the technique of astrometric mass determination to measure the masses of 21 main-belt asteroids; the masses of 9 Metis (1.03 ± 0.24 × 10-11 M), 17 Thetis (6.17 ± 0.64 × 10-13 M), 19 Fortuna (5.41 ± 0.76 × 10-12 M), and 189 Phthia (1.87 ± 0.64 × 10-14 M) appear to be new. The resulting bulk porosities of 11 Parthenope (12±4%) and 16 Psyche (46±16%) are smaller than previously-reported values. Empirical expressions modeling bulk density as a function of mean radius are presented for the C and S taxonomic classes. To accurately model the forces on these asteroids during the mass determination process, we created an integrated ephemeris of the 300 large asteroids used in preparing the DE-405 planetary ephemeris; this new BC-405 integrated asteroid ephemeris also appears useful in other high-accuracy applications.


N-body Asteroid Ephemerides Asteroid masses Astrometric masses Asteroid porosity