(21187) Setsuo Main-belt Asteroid
Discovered on 31 March 1994 by Endate, K., Watanabe, K. at Kitami.
Setsuo Fukushima (b. 1961) was moved by astronomical images he first saw in middle school. His work as a volunteer lecturer at the Children's Astronomical Classroom at the Takamatsu City Planetarium spans over ten years.Naming citation (MPC batch dated 2018-09-25), IAU / Minor Planet Center, via NASA/JPL
Where Setsuo is today
Seen from above the solar system on 2026-10-14: Setsuo is 2.11 au from the Sun and 3.03 au from Earth. Computed from JPL's orbital elements.
Facts
| Number | 21187 |
| Provisional designation | 1994 FY |
| Orbit class | Main-belt Asteroid |
| Diameter | 4.31 km (#12,022 largest of 17,440 named asteroids with a measured size) |
| Albedo | 0.218 |
| Absolute magnitude (H) | 14.4 |
| Orbital period | 3.64 years |
| Semi-major axis | 2.36 au |
| Perihelion – aphelion | 2.11 – 2.62 au |
| Eccentricity | 0.109 |
| Inclination | 12.1° |
| Closest distance between its orbit and Earth's (MOID) | 1.12 au |
Data: NASA/JPL Small-Body Database and the IAU Minor Planet Center.