(21148) Billramsey Main-belt Asteroid
Discovered on 16 April 1993 by Shoemaker, C. S., Shoemaker, E. M. at Palomar.
William D. Ramsey (b. 1934) helped organize and inventory the Palomar Observatory's 1.2-m Oschin Telescope plate archive. He also helped refurbish for public display the famous Michelson 6-meter interferometer, which was used atop the Hooker 2.5-m telescope at the Mt. Wilson Observatory.Naming citation (20030318/MPCPages.arc), IAU / Minor Planet Center, via NASA/JPL
Where Billramsey is today
Seen from above the solar system on 2026-10-14: Billramsey is 3.11 au from the Sun and 2.25 au from Earth. Computed from JPL's orbital elements.
Facts
| Number | 21148 |
| Provisional designation | 1993 HN1 |
| Orbit class | Main-belt Asteroid |
| Diameter | 9.93 km (#5,145 largest of 17,440 named asteroids with a measured size) |
| Albedo | 0.0380 |
| Rotation period | 27.1 hours |
| Absolute magnitude (H) | 13.93 |
| Orbital period | 4.40 years |
| Semi-major axis | 2.69 au |
| Perihelion – aphelion | 2.18 – 3.19 au |
| Eccentricity | 0.189 |
| Inclination | 12.9° |
| Closest distance between its orbit and Earth's (MOID) | 1.19 au |
Data: NASA/JPL Small-Body Database and the IAU Minor Planet Center.
Also named after someone called William
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- (4838) Billmclaughlin
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- (5763) Williamtobin
- (6012) Williammurdoch
- (6613) Williamcarl
- (6756) Williamfeldman
All asteroids named after someone called William
Also discovered on 16 April 1993
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- (9375) Omodaka
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