(3999) Aristarchus Main-belt Asteroid
Discovered on 5 January 1989 by T. Kojima at Chiyoda.
Where Aristarchus is today
Seen from above the solar system on 2026-10-14: Aristarchus is 2.59 au from the Sun and 1.60 au from Earth. Computed from JPL's orbital elements.
Facts
| Number | 3999 |
| Provisional designation | 1989 AL |
| Orbit class | Main-belt Asteroid |
| Diameter | 18.3 km (#2,453 largest of 17,440 named asteroids with a measured size) |
| Albedo | 0.0410 |
| Rotation period | 12.6 hours |
| Absolute magnitude (H) | 12.78 |
| Orbital period | 3.86 years |
| Semi-major axis | 2.46 au |
| Perihelion – aphelion | 2.17 – 2.75 au |
| Eccentricity | 0.119 |
| Inclination | 2.54° |
| Closest distance between its orbit and Earth's (MOID) | 1.18 au |
Data: NASA/JPL Small-Body Database and the IAU Minor Planet Center.