(29) Amphitrite

From Wikipedia:
29 Amphitrite (233*212*193 km) is one of the largest S-type asteroids, probably third in diameter after Eunomia and Juno.

S-type asteroids are of a stony composition, hence the name. Approximately 17% of asteroids are of this type, making it the second most common after the C-type (carbonaceous type, 75% of asteroids).

Amphirite's orbit is less eccentric and inclined than those of its larger cousins; indeed, it is the most circular of any asteroid discovered up to that point. As a consequence, it never becomes as bright as Iris or Hebe, especially as it is much further from the Sun than those asteroids. It can reach magnitudes of around +8.6 at a favorable opposition, but usually is around the binocular limit of +9.5.

A satellite of the asteroid is suspected to exist, based on lightcurve data collected by Edward F. Tedesco.
  • Tedesco, E. F. (March 1979). "Binary Asteroids: Evidence for Their Existence from Lightcurves". Science, New Series 203 (4383): 905907.
  • van Flandern, T. C.; Tedesco, E. F.; Binzel, R. P. (1979). "Satellites of asteroids". Asteroids. Tucson, AZ: University of Arizona Press. pp. 443465.
Amphitrite was discovered by Albert Marth on March 1, 1854, at the private South Villa Observatory, in Regent's Park, London.

Link to CdR-CdL website: Click here


Observation Francois KUGEL with
  • 80mm F/5 refractor
  • ST8300 SBig CCD camera (2x2 binning)
  • IR 742nm cut-off filter
Processing Jerome CARON with AsPyLib library.

Official (MPC, Harris database) Measured (fit with 6 Fourier terms)
Rotation period (hours) 5.390 5.3886 +/- 0.0010
Rotation period (days) 0.2246 0.22453 +/- 0.00004
Amplitude of mag variations 0.01-0.15 0.146

Magnitude during the observations: 10.7

Searching the period

Search of best fit using 4 harmonics.
Most likely period = 0.2245 days, this value corresponds to the official period.