Kalliope I Linus is an asteroid moon

Asteroid moon

A minor planet moon is an astronomical body that orbits a minor planet as its natural satellite. It is thought that many asteroids and Kuiper belt objects may possess moons, in some cases quite substantial in size...

 that orbits the large M-type asteroid

M-type asteroid

M-type asteroids are asteroids of partially known composition; they are moderately bright . Some, but not all, are made of nickel-iron, either pure or mixed with small amounts of stone. These are thought to be pieces of the metallic core of differentiated asteroids that were fragmented by impacts,...

 22 Kalliope

22 Kalliope

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

. It was discovered on August 29, 2001, by astronomers Jean-Luc Margot

Jean-Luc Margot

Jean-Luc Margot is a Belgian-born astronomer and a Professor at UCLA. He specializes in planetary sciences. He was awarded the H. C. Urey Prize by the American Astronomical Society in 2004....

 and Michael E. Brown

Michael E. Brown

Michael E. Brown has been a professor of planetary astronomy at the California Institute of Technology since 2003....

 with the Keck telescope. Another team also detected the moon with the Canada-France-Hawaii Telescope

Canada-France-Hawaii Telescope

The Canada–France–Hawaii Telescope is located near the summit of Mauna Kea mountain on Hawaii's Big Island at an altitude of 4,204 meters , and is one of the observatories that comprise the Mauna Kea Observatory...

 on September 2, 2001. Both telescopes are on Mauna Kea

Mauna Kea

Mauna Kea is a volcano on the island of Hawaii. Standing above sea level, its peak is the highest point in the state of Hawaii. However, much of the mountain is under water; when measured from its oceanic base, Mauna Kea is over tall—significantly taller than Mount Everest...

. It received the provisional designation S/2001 (22) 1, and was named on August 8, 2003, after the mythological Linus

Linus (mythology)

In Greek mythology Linus refers to the musical son of Oeagrus, nominally Apollo, and the Muse Calliope. As the son of Apollo and a Muse, either Calliope or Terpsichore, he is considered the inventor of melody and rhythm. Linus taught music to his brother Orpheus and then to Heracles. Linus went...

, son of the muse Calliope

Calliope

In Greek mythology, Calliope was the muse of epic poetry, daughter of Zeus and Mnemosyne, and is now best known as Homer's muse, the inspiration for the Odyssey and the Iliad....

 and the inventor of melody and rhythm.

With an estimated diameter, Linus is very large compared to most asteroid moons, and in fact would be a sizable asteroid by itself. The only known larger moons in the main belt are the smaller components of the double asteroids 617 Patroclus

617 Patroclus

617 Patroclus is a binary minor planet made up of two similarly-sized objects orbiting their common centre of gravity. It is a Trojan asteroid, sharing an orbit with Jupiter. It was discovered in 1906 by August Kopff, and was the second trojan to be discovered...

 and 90 Antiope

90 Antiope

The most remarkable feature of Antiope is that it consists of two components of almost equal size , making it a truly "double" asteroid. Its binary nature was discovered on 10 August 2000 by a group of astronomers using adaptive optics at the Keck Telescope on Mauna Kea. The "secondary" is...

.

It has been estimated that Linus' orbit precesses

Precession

Precession is a change in the orientation of the rotation axis of a rotating body. It can be defined as a change in direction of the rotation axis in which the second Euler angle is constant...

 at quite a rapid rate, making one cycle in several years. This is attributed primarily to the non-spherical shape of Kalliope. Linus's brightness has varied appreciably between observations, which may indicate that its shape is elongated.

Linus may have formed out of impact

Impact event

An impact event is the collision of a large meteorite, asteroid, comet, or other celestial object with the Earth or another planet. Throughout recorded history, hundreds of minor impact events have been reported, with some occurrences causing deaths, injuries, property damage or other significant...

 ejecta

Ejecta

Ejecta can mean:*In volcanology, particles that came out of a volcanic vent, traveled through the air or under water, and fell back on the ground surface or on the ocean floor...

 from a collision

Collision

A collision is an isolated event which two or more moving bodies exert forces on each other for a relatively short time.Although the most common colloquial use of the word "collision" refers to accidents in which two or more objects collide, the scientific use of the word "collision" implies...

 with Kalliope or a fragment captured after disruption of a parent asteroid (a proto-Kalliope).

External links

• IAUC 7703, announcing Linus' discovery
• IAUC 8177, announcing Linus' naming
• Link to the Linus discovery paper , "A Low-Density M-type Asteroid in the Main Belt"
• Kalliope and Linus very well resolved with the 8m VLT
  Very Large Telescope
  The Very Large Telescope is a telescope operated by the European Southern Observatory on Cerro Paranal in the Atacama Desert of northern Chile. The VLT consists of four individual telescopes, each with a primary mirror 8.2m across, which are generally used separately but can be used together to...
  
  
• orbit diagram for Linus
• Information on Kalliope, Linus' orbit and several images
• A different VLT image of Kalliope and Linus
• another image of Kalliope and Linus