| Orbital diagram | |
| Discovery | |
|---|---|
| Discovered by | R. Luther |
| Discovery site | Bilk Obs. |
| Discovery date | 12 March 1871 |
| Designations | |
| (113) Amalthea | |
| Pronunciation | /æməlˈθiːə/ |
Named after | Amalthea |
| A871 EA; 1931 TN3; 1951 CY | |
| main-belt · Flora | |
| Orbital characteristics [1] | |
| 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) | |
| Eccentricity | 0.086651 |
| 3.66 yr (1337.7 d) | |
| 226.48° | |
| 0° 16m 8.832s / day | |
| Inclination | 5.0422° |
| 123.486° | |
| 79.118° | |
| Known satellites | 1 [2] |
| Physical characteristics | |
Mean diameter | 46.14±1.4 km |
| 9.950 h (0.4146 d) | |
| 0.2649±0.017 | |
| S | |
| 8.74 | |
113 Amalthea ( /æməlˈθiːə/ ) is a stony Florian asteroid and binary system from the inner regions of the asteroid belt, approximately 50 kilometers (31 miles) in diameter. It was discovered on 12 March 1871, by German astronomer Robert Luther at the Bilk Observatory in Düsseldorf, Germany. The elongated S-type asteroid has a rotation period of 9.95 hours. It was named after Amalthea from Greek mythology. A purported satellite of Amalthea was announced in July 2017, but was later found to be a software error in July 2021. [3]
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. [4] The spectrum of Amalthea reveals the presence of the mineral olivine, a relative rarity in the asteroid belt. [5] [6]
Based on observations made during a stellar occultation by Amalthea of a 10th-magnitude star on 14 March 2017, it was announced in July 2017 that the asteroid has a small, 5-kilometer-sized satellite, provisionally designated S/2017 (113) 1. However, the satellite was later retracted as a software-reduction coding error on 17 July 2021. [3] The occultation also indicated that Amalthea has a distinctly elongated shape. [2]
One of Jupiter's inner small satellites, unrelated to 113 Amalthea, is also called Amalthea, as is a (apparently fictional) small Arjuna asteroid in Neal Stephenson's 2015 novel Seveneves .
Metis is one of the larger main-belt asteroids. It is composed of silicates and metallic nickel-iron, and may be the core remnant of a large asteroid that was destroyed by an ancient collision. Metis is estimated to contain just under half a percent of the total mass of the asteroid belt.
Parthenope is a large, bright main-belt asteroid.
Egeria is a large main-belt G-type asteroid. It was discovered by Annibale de Gasparis on November 2, 1850. Egeria was named by Urbain Le Verrier, whose computations led to the discovery of Neptune, after the mythological nymph Egeria of Aricia, Italy, the wife of Numa Pompilius, second king of Rome.
Melpomene is a large, bright main-belt asteroid that was discovered by J. R. Hind on 24 June 1852, and named after Melpomenē, the Muse of tragedy in Greek mythology. It is classified as an S-type asteroid and is composed of silicates and metals. This asteroid is orbiting the Sun at a distance of 2.296 AU with a period of 3.48 years and an eccentricity (ovalness) of 0.22. The orbital plane is tilted at an angle of 10.1° to the plane of the ecliptic.
Laetitia is a large main-belt asteroid that was discovered by French astronomer Jean Chacornac on 9 February 1856 and named after Laetitia, a minor Roman goddess of gaiety. The spectrum matches an S-type, indicating a stony (silicate) composition. It is orbiting the Sun with a period of 4.61 years and is spinning on its axis once every 5.1 hours.
Daphne is a large asteroid from the asteroid belt. It is a dark-surfaced body 174 km in diameter is probably composed of primitive carbonaceous chondrites. The spectra of the asteroid displays evidence of aqueous alteration. It was discovered by H. Goldschmidt on May 22, 1856, and named after Daphne, the nymph in Greek mythology who was turned into a laurel tree. Incorrect orbital calculations initially resulted in 56 Melete being mistaken for a second sighting of Daphne. Daphne was not sighted again until August 31, 1862.
Io is carbonaceous asteroid in the central region of the asteroid belt, approximately 170 kilometers in diameter. It is an identified Eunomian interloper.

Lachesis is a large main-belt asteroid. It was discovered by French astronomer Alphonse Borrelly on April 10, 1872, and independently by German-American astronomer Christian Heinrich Friedrich Peters on April 11, 1872, then named after Lachesis, one of the Moirai, or Fates, in Greek mythology. A Lachesean occultation of a star occurred in 1999 and was confirmed visually by five observers and once photoelectrically, with the chords yielding an estimated elliptical cross-section of 184 × 144 km.
Lucina is a main-belt asteroid that was discovered by Alphonse Borrelly on June 8, 1875, and named after Lucina, the Roman goddess of childbirth. It is large, dark and has a carbonaceous composition. The spectra of the asteroid displays evidence of aqueous alteration.

Kalliope is a large M-type asteroid from the asteroid belt discovered by J. R. Hind on 16 November 1852. It is named after Calliope, the Greek Muse of epic poetry. It is orbited by a small moon named Linus.

164 Eva is a main-belt asteroid that was discovered by the French brothers Paul Henry and Prosper Henry on July 12, 1876, in Paris. The reason the name Eva was chosen remains unknown. The orbital elements for 164 Eva were published in 1877 by American astronomer Winslow Upton. It is categorized as a C-type asteroid and is probably composed of primitive carbonaceous chondritic materials.
Nausikaa is a large main-belt S-type asteroid. It was discovered by Johann Palisa on February 17, 1879, at Pula, then in Austria, now in Croatia. The name derives from Nausicaä, a princess in Homer's Odyssey.
Athamantis is a fairly large main-belt asteroid that was discovered by the German-Austrian astronomer K. de Ball on September 3, 1882, in Bothkamp. It was his only asteroid discovery. The asteroid was named after Athamantis, daughter of Athamas the mythical Greek king of Orchomenus.
Nenetta is an A-type asteroid with a diameter of 38 km. It was discovered by Auguste Charlois on 10 March 1890 in Nice, France. The asteroid is orbiting the Sun at a distance of 2.87 AU with an eccentricity (ovalness) of 0.204 and an orbital period of 4.87 yr. The orbital plane is inclined at an angle of 6.7° to the plane of the ecliptic.

Bamberga is one of the largest asteroids in the asteroid belt. It was discovered by Johann Palisa on 25 February 1892 in Vienna. It is one of the top-20 largest asteroids in the asteroid belt. Apart from the near-Earth asteroid Eros, it was the last asteroid which is ever easily visible with binoculars to be discovered.
Dembowska is a large asteroid of the main belt, discovered on 9 December 1892, by the French astronomer Auguste Charlois while working at the observatory in Nice, France. It is named in honor of the Baron Hercules Dembowski, an Italian astronomer who made significant contributions to research on double and multiple stars.
4029 Bridges, provisional designation 1982 KC1, is a stony asteroid and binary system from the middle regions of the asteroid belt, approximately 8 kilometers in diameter.
4672 Takuboku, provisional designation 1988 HB, is a background asteroid from the outer regions of the asteroid belt, approximately 35 kilometers in diameter. It was discovered on 17 April 1988, by Japanese astronomers Seiji Ueda and Hiroshi Kaneda at the Kushiro Observatory on Hokkaido, Japan. The asteroid was named after the Japanese poet Takuboku Ishikawa. In 2005, measurement of the body's occultation ellipse also gave 35.0 × 35.0 kilometers.
5176 Yoichi, provisional designation 1989 AU, is a background asteroid from the central regions of the asteroid belt, approximately 17 kilometers in diameter. It was discovered on 4 January 1989, by Japanese astronomers Seiji Ueda and Hiroshi Kaneda at the Kushiro Observatory on Hokkaido, Japan. The likely elongated asteroid has a brightness variation of 0.45 magnitude, and occulted a star in the constellation Cetus in November 2014. It was named for the Japanese town of Yoichi.

15094 Polymele is a primitive Jupiter trojan from the Greek camp, approximately 21 kilometers in diameter. It is a target of the Lucy mission with a close flyby planned to occur in September 2027. It was discovered on 17 November 1999, by astronomers with the Catalina Sky Survey at Mount Lemmon Observatory, Arizona, in the United States. The P-type asteroid has a rotation period of 5.9 hours and highly flattened shape. It was named after Polymele from Greek mythology, the wife of Menoetius and the mother of Patroclus. In 2022, it was reported to have a natural satellite approximately 5 kilometers in diameter.