(19727) Allen Main-belt Asteroid
Discovered on 4 December 1999 by C. W. Juels at Fountain Hills.
London-based solar physicist Clabon Walter Allen (1904-1987) authored the first (1955) through third (1973) editions of Astrophysical Quantities, without which most professional astronomers would never have received their degrees, and most watchers of the sky would never have successfully completed their observing sessions.Naming citation (20060613/MPCPages.arc), IAU / Minor Planet Center, via NASA/JPL
👶 Allen as a baby name🐶 Allen as a dog name
Where Allen is today
Seen from above the solar system on 2026-10-14: Allen is 2.86 au from the Sun and 2.15 au from Earth. Computed from JPL's orbital elements.
Facts
| Number | 19727 |
| Provisional designation | 1999 XS2 |
| Orbit class | Main-belt Asteroid |
| Diameter | 5.95 km (#9,010 largest of 17,440 named asteroids with a measured size) |
| Albedo | 0.262 |
| Absolute magnitude (H) | 13.16 |
| Orbital period | 3.79 years |
| Semi-major axis | 2.43 au |
| Perihelion – aphelion | 1.97 – 2.89 au |
| Eccentricity | 0.190 |
| Inclination | 13.4° |
| Closest distance between its orbit and Earth's (MOID) | 0.977 au |
Data: NASA/JPL Small-Body Database and the IAU Minor Planet Center.
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