113 Amalthea () is a stony Florian

asteroid An asteroid is a minor planet of the inner Solar System. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter; they are rocky, metallic or icy bodies with no atmosphere. ...

and

binary system A binary system is a system of two astronomical bodies which are close enough that their gravitational attraction causes them to orbit each other around a barycenter ''(also see animated examples)''. More restrictive definitions require that th ...

from the inner regions of the

asteroid belt The asteroid belt is a torus-shaped region in the Solar System, located roughly between the orbits of the planets Jupiter and Mars. It contains a great many solid, irregularly shaped bodies, of many sizes, but much smaller than planets, called ...

, approximately in diameter. It was discovered on 12 March 1871, by German astronomer

Robert Luther Karl Theodor Robert Luther (April 16, 1822, Świdnica – February 15, 1900 Düsseldorf), normally published as Robert Luther, was a German astronomer. While working at the Bilk Observatory in Düsseldorf, Germany, he searched for asteroids and ...

at the

Bilk Observatory Bilk is a quarter (''Stadtteil'') of Düsseldorf. Together with Oberbilk, Unterbilk, Hamm, Flehe and Volmerswerth it constitutes Borough 3, which is the most populous borough of Düsseldorf. Bilk has an area of , and 41,150 inhabitants (2020) ...

in Düsseldorf, Germany. The elongated

S-type asteroid S-type asteroids are asteroids with a spectral type that is indicative of a siliceous (i.e. stony) mineralogical composition, hence the name. They have relatively high density. Approximately 17% of asteroids are of this type, making it the secon ...

has a rotation period of 9.95 hours. It was named after Amalthea from

Greek mythology A major branch of classical mythology, Greek mythology is the body of myths originally told by the Ancient Greece, ancient Greeks, and a genre of Ancient Greek folklore. These stories concern the Cosmogony, origin and Cosmology#Metaphysical co ...

. A purported

satellite A satellite or artificial satellite is an object intentionally placed into orbit in outer space. Except for passive satellites, most satellites have an electricity generation system for equipment on board, such as solar panels or radioisotope ...

of ''Amalthea'' was announced in July 2017, but was later found to be a software error in July 2021.

Description

''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 Metis (minor planet designation: 9 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 esti ...

. The spectrum of ''Amalthea'' reveals the presence of the mineral

olivine The mineral olivine () is a magnesium iron silicate with the chemical formula . It is a type of nesosilicate or orthosilicate. The primary component of the Earth's upper mantle, it is a common mineral in Earth's subsurface, but weathers quickl ...

, a relative rarity in the asteroid belt. Based on observations made during a stellar

occultation An occultation is an event that occurs when one object is hidden from the observer by another object that passes between them. The term is often used in astronomy, but can also refer to any situation in which an object in the foreground blocks ...

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

, provisionally designated ''S/2017 (113) 1''. However, the satellite was later retracted as a software-reduction coding error on 17 July 2021. The occultation also indicated that ''Amalthea'' has a distinctly elongated shape. One of

Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but ...

's inner small satellites, unrelated to 113 Amalthea, is also called Amalthea, as is a (apparently fictional) small

Arjuna asteroid The Arjuna asteroids (also known as "Arjunas") are a dynamical group of asteroids in the Solar System. Arjunas are near-Earth objects (NEOs) whose orbits are very Earth-like in character, having low inclination, orbital periods close to one year, ...

in Neal Stephenson's 2015 novel ''

Seveneves ''Seveneves'' is a hard science fiction novel by Neal Stephenson published in 2015. The story tells of the desperate efforts to preserve '' Homo sapiens'' in the wake of apocalyptic events on Earth after the unexplained disintegration of the M ...

''.

References

External links

(113) Amalthea and S/2017 (113) 1
Asteroids with Satellites Database, Johnston's Archive * * {{DEFAULTSORT:Amalthea 000113 Discoveries by Robert Luther Named minor planets 000113 000113 000113 18710312