4660 Nereus

4660 Nereus
Nereus imaged by NASA's Goldstone Solar System Radar on its close approach in 2021
Discovery[1]
Discovered byEleanor F. Helin
Discovery site1.22-m Samuel Oschin telescope
Discovery date28 February 1982
Designations
(4660) Nereus
Pronunciation/ˈnɪəriəs/ NEER-ee-əs[2]
Named after
Νηρεύς Nēreús
Apollo Apollo
PHA[3]
Orbital characteristics[3]
Epoch 2021-Jul-01 (JD 2459396.5)
Uncertainty parameter 0
Observation arc14647 days (40.10 yr)
Aphelion2.0250 AU (303 million km)
Perihelion0.95287 AU (143 million km)
1.4889 AU (223 million km)
Eccentricity0.36004
1.82 yr (663.62 d)
256.71°
0° 32m 33.371s / day
Inclination1.4316°
314.41°
158.12°
Earth MOID0.0031 AU (460 thousand km)
Physical characteristics
Dimensions
  • X = 510±20 m
  • Y = 330±20 m
  • Z = 241+80
    −10
     m
    [4]
0.165 km
0.33+0.04
−0.01
 km2
[4]
Volume0.019±0.003 km3[4]
15.1 h (0.63 d)
15.16[4]
+80°[4]
+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]

Close approaches[3]
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]

  1. ^ a b Cite error: The named reference discovery was invoked but never defined (see the help page).
  2. ^ "Nereus". Merriam-Webster.com Dictionary. Merriam-Webster.
  3. ^ a b c d e f Cite error: The named reference jpldata was invoked but never defined (see the help page).
  4. ^ a b c d e f g h Cite error: The named reference radar was invoked but never defined (see the help page).
  5. ^ Cite error: The named reference transfer-costs was invoked but never defined (see the help page).
  6. ^ a b c Cite error: The named reference neodys was invoked but never defined (see the help page).
  7. ^ "NEO Groups". Near Earth Object Program. NASA. Archived from the original on 2 November 2016.
  8. ^ Cite error: The named reference Horizons2166 was invoked but never defined (see the help page).