(21774) O'Brien Main-belt Asteroid
Discovered on 3 September 1999 by LONEOS at Anderson Mesa.
David P. O'Brien (b. 1976) is a planetary scientist at the Planetary Science Institute, Tucson. He studies collisional evolution of main-belt minor planets, cratering on (951) Gaspra and other objects, as well as primordial sculpting of the main belt during the planetary accretion process.Naming citation (20080718/MPCPages.arc), IAU / Minor Planet Center, via NASA/JPL
Where O'Brien is today
Seen from above the solar system on 2026-10-14: O'Brien is 2.47 au from the Sun and 3.47 au from Earth. Computed from JPL's orbital elements.
Facts
| Number | 21774 |
| Provisional designation | 1999 RR217 |
| Orbit class | Main-belt Asteroid |
| Rotation period | 27.4 hours |
| Absolute magnitude (H) | 15.71 |
| Orbital period | 3.58 years |
| Semi-major axis | 2.34 au |
| Perihelion – aphelion | 2.14 – 2.54 au |
| Eccentricity | 0.0839 |
| Inclination | 6.66° |
| Closest distance between its orbit and Earth's (MOID) | 1.17 au |
Data: NASA/JPL Small-Body Database and the IAU Minor Planet Center.
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