 Nereus imaged by NASA's Goldstone Solar System Radar on its close approach in 2021 | |
| Discovery[1] | |
|---|---|
| Discovered by | Eleanor F. Helin |
| Discovery site | 1.22-m Samuel Oschin telescope |
| Discovery date | 28 February 1982 |
| Designations | |
| (4660) Nereus | |
| Pronunciation | /ˈnɪəriəs/ NEER-ee-əs[2] |
Named after | Νηρεύς Nēreús |
Apollo  PHA[3] | |
| Orbital characteristics[3] | |
| Epoch 2021-Jul-01 (JD 2459396.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 14647 days (40.10 yr) |
| Aphelion | 2.0250 AU (303 million km) |
| Perihelion | 0.95287 AU (143 million km) |
| 1.4889 AU (223 million km) | |
| Eccentricity | 0.36004 |
| 1.82 yr (663.62 d) | |
| 256.71° | |
| 0° 32m 33.371s / day | |
| Inclination | 1.4316° |
| 314.41° | |
| 158.12° | |
| Earth MOID | 0.0031 AU (460 thousand km) |
| Physical characteristics | |
| Dimensions |
|
| 0.165 km | |
| 0.33+0.04 −0.01 km2[4] | |
| Volume | 0.019±0.003 km3[4] |
| 15.1 h (0.63 d) | |
| 15.16[4] | |
Pole ecliptic latitude | +80°[4] |
Pole ecliptic longitude | +25°[4] |
| 0.54+0.03 −0.09[4] | |
| Xe | |
| 12.6 (2021 peak) 9.8 (2060 peak) | |
| 18.2±0.7[3] | |
4660 Nereus, provisional designation 1982 DB, is a small (about 0.33 kilometres (0.21 mi)) asteroid. It was discovered by Eleanor F. Helin on 28 February 1982, approximately a month after it passed 4.1 million km (11 LD) from Earth.[1]
Nereus is potentially an important asteroid with a high albedo. It is an Apollo and Mars-crosser, with an orbit that frequently comes close to Earth, and because of this it is exceptionally accessible to spacecraft. Indeed, because of its small size and close orbit, its delta-V for rendezvous of ~5 km/s is smaller than the Moon's, which is about 6.3 km/s.[5]
Nereus makes seven approaches to Earth of less than 5 million km between 1900 and 2100.[6] The closest will be on 14 February 2060, at 1.2 million km.[6] The most recent closest approach was on 11 December 2021, when it was 3.9 million km away.[6] During the 2021 approach, the asteroid peaked around apparent magnitude 12.6, requiring a telescope with around a 100mm objective lens to be visually seen. Its orbital period of 1.82 yr[3] also puts it somewhat near a 2:1 orbital resonance with Earth, which means that an approximately 4-year mission could depart for and return from the asteroid on relatively near passes to the Earth.[citation needed]
Nereus is classified as a potentially hazardous asteroid (PHA),[3] due to both its absolute magnitude (H ≤ 22) and its minimum orbit intersection distance (MOID ≤ 0.05 AU).[7]
| Date | JPL SBDB nominal geocentric distance |
uncertainty region (3-sigma) |
|---|---|---|
| 2021-12-11 | 3934242 km | ± 3 km |
| 2060-02-14 | 1198007 km | ± 234 km |
| 2166-02-03 | 2800000 km | ± 261 thousand km[8] |
The asteroid is classified as E-type, so it could be potentially associated with aubrite meteorites (enstatite achondrites).[4]
- ^ a b Cite error: The named reference
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