(458732) 2011 MD5
(458732) 2011 MD5 is an Apollo near-Earth asteroid around 1.2 kilometers (0.75 miles) in diameter. It is the largest asteroid known to have passed closer than the Moon. On 17 September 1918 the asteroid passed 0.00234 AU (350 thousand km; 0.91 LD) from Earth with a peak apparent magnitude of around 8.4. The 1918 close approach distance is known with an accuracy of roughly ±120 km. The asteroid had come to opposition (opposite the Sun in the sky) on 9 August 1918 at magnitude 16.
| Discovery | |
|---|---|
| Discovered by | Pan-STARRS 1 |
| Discovery site | Haleakala Obs. |
| Discovery date | 30 June 2011 |
| Designations | |
MPC designation | (458732) 2011 MD5 |
Alternative designations | 2011 MD5 |
Minor planet category |
|
| Orbital characteristics | |
| Epoch 31 May 2020 (JD 2459000.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 8.67 yr (3,165 d) |
| Aphelion | 3.9869 AU |
| Perihelion | 0.9895 AU |
Semi-major axis | 2.4882 AU |
| Eccentricity | 0.6023 |
Orbital period (sidereal) | 3.92 yr (1,434 d) |
Mean anomaly | 49.188° |
Mean motion | 0° 15m 3.96s / day |
| Inclination | 10.553° |
Longitude of ascending node | 170.34° |
| 224.84° | |
| Earth MOID | 0.0627 AU (24.4 LD) |
| Physical characteristics | |
Mean diameter | 730–1600 m (CNEOS) 0.8 km 1.2 km |
| 17.8 17.9 | |
2011 MD5 was not discovered until 30 June 2011, when the asteroid was 1.3 AU (190 million km) from Earth. As of 2023, the asteroid has a 12-year observation arc and a well determined orbit.
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