(173117) Promachus Jupiter Trojan
Discovered on 24 September 1973 by van Houten, C. J., van Houten-Groeneveld, I., Gehrels, T. at Palomar.
Promachus was a Greek warrior in the Iliad who was killed by the Trojan hero Acamas.Naming citation (20080520/MPCPages.arc), IAU / Minor Planet Center, via NASA/JPL
Where Promachus is today
Seen from above the solar system on 2026-10-14: Promachus is 5.80 au from the Sun and 6.80 au from Earth. Computed from JPL's orbital elements.
Facts
| Number | 173117 |
| Provisional designation | 1973 SA1 |
| Orbit class | Jupiter Trojan |
| Diameter | 13.2 km (#3,664 largest of 17,440 named asteroids with a measured size) |
| Albedo | 0.0850 |
| Absolute magnitude (H) | 12.86 |
| Orbital period | 11.8 years |
| Semi-major axis | 5.18 au |
| Perihelion – aphelion | 4.55 – 5.81 au |
| Eccentricity | 0.121 |
| Inclination | 7.77° |
| Closest distance between its orbit and Earth's (MOID) | 3.56 au |
Data: NASA/JPL Small-Body Database and the IAU Minor Planet Center.