(9686) Keesom Main-belt Asteroid
Discovered on 24 September 1960 by van Houten, C. J., van Houten-Groeneveld, I., Gehrels, T. at Palomar.
Dutch physicist Willem Hendrik Keesom (1876-1956) specialized in cryogenics. In 1926 he became the first to solidify helium, and among his discoveries are He I and He II. In 1932 he achieved the temperature of -272° C, only one degree above absolute zero. The name was suggested by W. A. Fröger.Naming citation (20010705/MPCPages.arc), IAU / Minor Planet Center, via NASA/JPL
Where Keesom is today
Seen from above the solar system on 2026-10-14: Keesom is 2.34 au from the Sun and 2.06 au from Earth. Computed from JPL's orbital elements.
Facts
| Number | 9686 |
| Provisional designation | 4604 P-L |
| Orbit class | Main-belt Asteroid |
| Diameter | 2.31 km (#16,584 largest of 17,440 named asteroids with a measured size) |
| Albedo | 0.250 |
| Absolute magnitude (H) | 15.38 |
| Orbital period | 3.44 years |
| Semi-major axis | 2.28 au |
| Perihelion – aphelion | 2.02 – 2.54 au |
| Eccentricity | 0.114 |
| Inclination | 2.32° |
| Closest distance between its orbit and Earth's (MOID) | 1.01 au |
Data: NASA/JPL Small-Body Database and the IAU Minor Planet Center.
Also named after someone called Willem
- (1964) Luyten
- (10436) Janwillempel
- (10652) Blaeu
- (10654) Bontekoe
- (10964) Degraaff
- (10984) Gispen
- (11240) Piso
- (11427) Willemkolff
- (12132) Wimfroger
- (12162) Bilderdijk
- (12175) Wimhermans
- (13045) Vermandere
All asteroids named after someone called Willem
Also discovered on 24 September 1960
- (1743) Schmidt
- (1744) Harriet
- (1776) Kuiper
- (1777) Gehrels
- (1795) Woltjer
- (1808) Bellerophon
- (1809) Prometheus
- (1810) Epimetheus
- (1811) Bruwer
- (1812) Gilgamesh
- (1846) Bengt
- (1868) Thersites