(20740) Semery Main-belt Asteroid
Discovered on 13 December 1999 by LONEOS at Anderson Mesa.
Alain Sémery (b. 1944) is an engineer at Paris Observatory. He has contributed to the design and development of many instruments aboard spacecraft involved in solar system exploration.Naming citation (20080718/MPCPages.arc), IAU / Minor Planet Center, via NASA/JPL
Where Semery is today
Seen from above the solar system on 2026-10-14: Semery is 2.63 au from the Sun and 2.31 au from Earth. Computed from JPL's orbital elements.
Facts
| Number | 20740 |
| Provisional designation | 1999 XB228 |
| Orbit class | Main-belt Asteroid |
| Diameter | 12.9 km (#3,759 largest of 17,440 named asteroids with a measured size) |
| Albedo | 0.0670 |
| Rotation period | 7.97 hours |
| Absolute magnitude (H) | 12.96 |
| Orbital period | 5.55 years |
| Semi-major axis | 3.14 au |
| Perihelion – aphelion | 2.62 – 3.65 au |
| Eccentricity | 0.164 |
| Inclination | 6.47° |
| Closest distance between its orbit and Earth's (MOID) | 1.61 au |
Data: NASA/JPL Small-Body Database and the IAU Minor Planet Center.
Also named after someone called Alain
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- (10222) Klotz
- (11158) Cirou
- (20759) Vienne
- (24988) Alainmilsztajn
- (33163) Alainaspect
- (41213) Mimoun
- (232409) Dubes
All asteroids named after someone called Alain
Also discovered on 13 December 1999
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- (25544) Renerogers
- (26435) Juliebrisset
- (33809) Petrescu
- (36264) Kojimatsumoto
- (67019) Hlohovec
- (121725) Aphidas