16 Psyche
16 Psyche (/ˈsaɪkiː/ SY-kee) is a large M-type asteroid, which was discovered by the Italian astronomer Annibale de Gasparis, on 17 March 1852 and named after the Greek goddess Psyche. The prefix "16" signifies that it was the sixteenth minor planet in order of discovery. It is the largest and most massive of the M-type asteroids, and one of the dozen most massive asteroids. It has a mean diameter of approximately 220 kilometers (140 mi) and contains about one percent of the mass of the asteroid belt. It was thought to be the exposed core of a protoplanet, but recent observations cast doubt on that hypothesis. Psyche will be explored by NASA, with a spacecraft of the same name, marking the first time a manmade object will journey to a metallic asteroid, launched on 13 October 2023, with an expected arrival in 2029.
| Discovery | |
|---|---|
| Discovered by | Annibale de Gasparis |
| Discovery site | Naples Observatory |
| Discovery date | 17 March 1852 |
| Designations | |
Designation | (16) Psyche |
| Pronunciation | /ˈsaɪkiː/ |
Named after | Psyche (Ψυχή) |
| Main belt | |
| Adjectives | Psychean (/saɪˈkiːən/) |
| Symbol | (historical) |
| Orbital characteristics | |
| Epoch 13 September 2023 (JD 2460200.5) | |
| Aphelion | 3.32 AU (497 million km) |
| Perihelion | 2.53 AU (378 million km) |
| 2.92 AU (437 million km) | |
| Eccentricity | 0.1342 |
| 4.999 yr (1825.95 d) | |
| 243.16° | |
| Inclination | 3.096° |
| 150.03° | |
| 27 April 2025 | |
| 229.41° | |
| Earth MOID | 1.53 AU (229 million km) |
| Physical characteristics | |
| Dimensions | c/a = 0.59±0.02 (278±5 × 232±6 × 164±4) km [best ellipsoid fit = 277 km × 238 km × 168 km] 279 × 232 × 189 km ( ± 10% ) (278+4 −8 × 238+4 −6 × 171+1 −5) km |
Mean diameter | 223±3 km 222±4 km 222+1 −4 km |
| Volume | 5.75×106 km3 (best fit) |
| Mass | (2.29±0.14)×1019 kg |
Mean density | 3.977±0.253 g/cm3 |
| ~0.144 m/s2 | |
| ~180 m/s (~600 ft/s) | |
| 4.195948±0.000001 h | |
| Albedo | 0.15±0.03 0.34±0.08 (radar) |
Spectral type | Tholen = M SMASS = X Bus-DeMeo = Xk |
| 9.22 to 12.19 | |
| 6.21 | |