|Discovered by||Karl Theodor Robert Luther|
|Discovery date||12 March 1871|
|MPC designation||(113) Amalthea|
|Epoch 31 July 2016 (JD 2457600.5)|
|Uncertainty parameter 0|
|Observation arc||144.90 yr (52926 d)|
|Aphelion||2.5819 AU (386.25 Gm)|
|Perihelion||2.17010 AU (324.642 Gm)|
|2.37598 AU (355.442 Gm)|
|3.66 yr (1337.7 d)|
Average orbital speed
|0° 16m 8.832s / day|
|Earth MOID||1.17323 AU (175.513 Gm)|
|Jupiter MOID||2.38628 AU (356.982 Gm)|
|Jupiter Tisserand parameter||3.531|
|Mass||1.0×1017 kg
7.8×1019 kg — 1.8×1020 kg[note 1]
Equatorial surface gravity
Equatorial escape velocity
|9.950 h (0.4146 d)|
113 Amalthea is a fairly typical rocky main-belt asteroid orbiting in the inner regions of the belt. It was discovered by R. Luther on March 12, 1871. The name comes from Amalthea of Greek mythology. One of Jupiter's inner small satellites, unrelated to 113 Amalthea, is also called Amalthea, as is an (apparently fictional) small Arjuna asteroid in Neal Stephenson's 2015 novel Seveneves.
Amalthea is thought to be a fragment from the mantle of a Vesta-sized, 300–600 km diameter parent body that broke up around one billion years ago, with the other major remnant being 9 Metis. The spectrum of 113 Amalthea reveals the presence of the mineral olivine, a relative rarity in the asteroid belt.
Based on observations made during an occultation by 113 Amalthea of a 10th-magnitude star on March 14, 2017, it was announced in July 2017 that the asteroid may have a small satellite. The observations also indicated that 113 Amalthea has a distinctly elongated shape.
- Yeomans, Donald K., "113 Amalthea", JPL Small-Body Database Browser, NASA Jet Propulsion Laboratory, retrieved 12 May 2016.
- Kelley, Michael S.; Gaffey, Michael J. (March 2000), "9 Metis and 113 Amalthea: A Genetic Asteroid Pair", Icarus, 35 (144), pp. 27–38, Bibcode:2000Icar..144...27K, doi:10.1006/icar.1999.6266.
- Cloutis, E. A. (March 1993), "Olivine-rich asteroids, pallasitic olivine and olivine-metal mixtures: Comparisons of reflectance spectra", Lunar and Planetary Institute, Twenty-fourth Lunar and Planetary Science Conference. Part 1: A-F, pp. 317–318, Bibcode:1993LPI....24..317C.
- Burbine, T. H.; et al. (July 2000), "The Nature of Olivine Asteroids", Meteoritics & Planetary Science, 35, pp. A35, Bibcode:2000M&PSA..35R..35B, doi:10.1111/j.1945-5100.2000.tb01796.x.
- Beatty, Kelly. "Amateur Observers Find an Asteroid's Moon". Sky & Telescope. Retrieved 15 July 2017.