(12639) Tonkoopman Main-belt Asteroid
Discovered on 29 September 1973 by van Houten, C. J., van Houten-Groeneveld, I., Gehrels, T. at Palomar.
Ton Koopman (b. 1944) is a Dutch harpsichord player and conductor, specializing in Baroque music. He founded the Amsterdam Baroque Orchestra in 1979, and the Amsterdam Baroque Choir in 1993. With these ensembles, he has given renowned performances of Bach's St. Matthew's Passion.Naming citation (MPC batch dated 2014-09-09), IAU / Minor Planet Center, via NASA/JPL
Where Tonkoopman is today
Seen from above the solar system on 2026-10-14: Tonkoopman is 2.53 au from the Sun and 3.52 au from Earth. Computed from JPL's orbital elements.
Facts
| Number | 12639 |
| Provisional designation | 1105 T-2 |
| Orbit class | Main-belt Asteroid |
| Diameter | 5.60 km (#9,571 largest of 17,440 named asteroids with a measured size) |
| Albedo | 0.0990 |
| Absolute magnitude (H) | 14.78 |
| Orbital period | 4.24 years |
| Semi-major axis | 2.62 au |
| Perihelion – aphelion | 2.26 – 2.98 au |
| Eccentricity | 0.137 |
| Inclination | 2.69° |
| Closest distance between its orbit and Earth's (MOID) | 1.28 au |
Data: NASA/JPL Small-Body Database and the IAU Minor Planet Center.
Also discovered on 29 September 1973
- (2049) Grietje
- (4357) Korinthos
- (4549) Burkhardt
- (4721) Atahualpa
- (4752) Myron
- (4876) Strabo
- (4978) Seitz
- (5151) Weerstra
- (5197) Rottmann
- (5243) Clasien
- (5244) Amphilochos
- (5266) Rauch