113 Amalthea


113 Amalthea is a stony Florian asteroid and binary system from the inner regions of the asteroid belt, approximately 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. The discovery of its 5-kilometer satellite was announced in July 2017.

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. The spectrum of Amalthea reveals the presence of the mineral olivine, a relative rarity in the asteroid belt.
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 1. The observations also indicated that Amalthea has a distinctly elongated shape.
One of Jupiter's inner small satellites, unrelated to 113 Amalthea, is also called Amalthea.