(458271) 2010 UM26 and 2010 RN221
(458271) 2010 UM26 and 2010 RN221 are a pair of sub-kilometer-sized asteroids that have extremely similar orbits in the main asteroid belt. These two asteroids are thought to have dissociated from a binary system sometime in the 2000s, which would make them one of the youngest asteroid pairs known. The largest member of this pair, (458271) 2010 UM26 (or simply 2010 UM26), is about 760 m (2,490 ft) in diameter and was discovered on 10 November 2006 by the Spacewatch survey at Kitt Peak Observatory. The smaller member, 2010 RN221, is about 350 m (1,150 ft) in diameter and was discovered on 11 September 2010 by the Mount Lemmon Survey at Mount Lemmon Observatory. It was not until February 2022 that astronomers began to recognize the similar orbits of these asteroids.
| Discovery | |
|---|---|
| Discovered by | Spacewatch (UM26) Mt. Lemmon Survey (RN221) |
| Discovery site | Kitt Peak Obs. (UM26) Mt. Lemmon Obs. (RN221) |
| Discovery date | 10 November 2006 (UM26) 11 September 2010 (RN221) |
| Designations | |
MPC designation | (458271) 2010 UM26 2010 RN221 |
Minor planet category | main-belt · (middle) |
| Orbital characteristics | |
| Epoch 13 September 2023 (JD 2460200.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 17.15 yr (6,265 days) |
| Earliest precovery date | 14 May 2005 |
| Aphelion | 3.415 AU |
| Perihelion | 1.738 AU |
Semi-major axis | 2.577 AU |
| Eccentricity | 0.3256 |
Orbital period (sidereal) | 4.14 yr (1,511 days) |
Mean anomaly | 65.868° (UM26) 65.863° (RN221) |
Mean motion | 0° 14m 17.877s / day (UM26) 0° 14m 17.875s / day (RN221) |
| Inclination | 3.883° |
Longitude of ascending node | 234.869° |
| 120.270° | |
| Physical characteristics: 3 | |
Mean diameter | 760 m (UM26) 350 m (RN221) |
Synodic rotation period | 5.9±0.6 h (UM26) ≥20 h (RN221) |
| ≈0.20 (assumed S-type): 3 | |
| 17.80 (UM26) 19.24±0.36 (RN221) | |