1979 XB
1979 XB is a lost asteroid with a short observation arc of 3.9 days that cannot be recovered with targeted observations and awaits serendipitous survey observations. It is classified as a near-Earth object and potentially hazardous asteroid of the Apollo group and is estimated to be 660 meters (2,200 feet) in diameter. The unnumbered minor planet has a poorly constrained orbit and has not been observed in 44 years. It has been listed on the Sentry Risk Table since the list started in 2002. With a cumulative Palermo Technical Impact Hazard Scale of −2.72, the poorly known orbit and assumed size place 1979 XB third on an unconstrained listing of the Sentry Risk Table.
| Discovery | |
|---|---|
| Discovered by | Siding Spring Obs. |
| Discovery site | Siding Spring Obs. |
| Discovery date | 11 December 1979 (first observed only) |
| Designations | |
| 1979 XB | |
| Lost · Apollo · NEO · PHA · risk listed | |
| Orbital characteristics | |
| Epoch 14 December 1979 (JD 2444221.5) | |
| Uncertainty parameter 9 | |
| Observation arc | 3.9 days |
| Aphelion | 3.8±0.7 AU (Q) |
| Perihelion | 0.65±0.01 AU (q) |
| 2.2±0.4 AU (a) | |
| Eccentricity | 0.7±0.06 (e) |
| 3.3±0.9 years | |
| 346°±4° (M) | |
| 0° 17m 46.68s / day | |
| Inclination | 24.7°±1.6° (i) |
| 86°±0.12° (Ω) | |
| 75.6°±0.7° (ω) | |
| Earth MOID | 0.02 AU (7.8 LD)? |
| Physical characteristics | |
Mean diameter | 660 m (est.) 500–1000 meters |
| 18.6? | |
1979 XB was first observed on 11 December 1979 by astronomers at the Siding Spring Observatory, Australia, when the asteroid was estimated to be 0.09 ± 0.02 AU (13.5 ± 3.0 million km) from Earth and had a solar elongation of 127°. The object has never been confirmed by a second observatory. The uncertainty region for this asteroid is now hundreds of millions of kilometers long.