| Minorplanet: | yes |
| 29 Amphitrite | |
| Symbol: | (historical) |
| Background: |
|
| Discovery Ref: |   |
| Discovery Site: | London |
| Discovered: | 1 March 1854 |
| Mpc Name: | (29) Amphitrite |
| Alt Names: | A899 NG |
| Pronounced: | [1] |
| Adjective: | Amphitritean, |
| Named After: | Amphitrite  |
| Mp Category: | main-belt  background  |
| Orbit Ref: |   |
| Epoch: | 23 March 2018 (JD 2458200.5) |
| Uncertainty: | 0 |
| Observation Arc: | 162.83 yr (59,472 d) |
| Perihelion: | 2.3712 AU |
| Semimajor: | 2.5556 AU |
| Eccentricity: | 0.0722 |
| Period: | 4.09 yr (1,492 d) |
| Mean Motion: | / day |
| Inclination: | 6.0823° |
| Asc Node: | 356.37° |
| Arg Peri: | 63.036° |
| Mean Diameter: | [2] |
| Flattening: | 0.18 |
| Mass: | (11.8±?) kg |
| Density: | |
| Albedo: | 0.194 |
| Spectral Type: | S  |
| Abs Magnitude: | 5.85 5.99 6.0 |
29 Amphitrite is one of the largest S-type asteroids, approximately 200km (100miles) in diameter, and probably fifth largest after Eunomia, Juno, Iris and Herculina.
Amphitrite was discovered by Albert Marth on 1 March 1854, at the private South Villa Observatory, in Regent's Park, London. It was Marth's only asteroid discovery. Its name was chosen by George Bishop, the owner of the observatory, who named it after Amphitrite, a sea goddess in Greek mythology. Its historical symbol was a shell and star; it is in the pipeline for Unicode 17.0 as U+1CECF .[3] [4]
Amphitrite'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.
In 2007, James Baer and Steven R. Chesley estimated Amphitrite to have a mass of 1.9 kg.[5] A more recent estimate by Baer suggests it has a mass of 1.18 kg.[6]
A satellite of the asteroid is suspected to exist, based on lightcurve data collected by Edward F. Tedesco.[7] [8] In 1988 a search for satellites or dust orbiting this asteroid was performed using the UH88 telescope at the Mauna Kea Observatories, but neither were found.
In 1984, while determining the Galileo mission's prelaunch trajectory to Jupiter, JPL engineers found out that if the spacecraft launched on May 1986, it could perform a flyby of 29 Amphitrite at a distance of on December 1, 1986. However, with the Challenger disaster delaying the launch to October 1989, the flyby was ultimately cancelled.