Menoetius (moon)

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(617) Patroclus I (Menoetius)
Provisional or systematic name S / 2001 (617) 1
Central body (617) Patroclus
Properties of the orbit
Major semi-axis (680 ± 20) km
Periapsis 666 km
Apoapsis 694 km
eccentricity 0.02 ± 0.02
Orbital time (4.283 ± 0.004) d
Mean orbital velocity 0.01154 km / s
Physical Properties
Albedo ≈ 0.047
Medium diameter (112.6 ± 3.2) km
Medium density (0.8 + 0.2 / -0.1) g / cm 3
Acceleration of gravity on the surface ≈ 0 m / s 2
Escape speed ≈ 0 m / s
Surface temperature 110 K
discovery
Explorer
  • WJ Merline
  • LM Close
  • N. Siegler
  • D. Potter
  • CR Chapman
  • C. Dumas
  • F. Menard
  • DC Slater
Date of discovery September 22, 2001
Remarks Smaller component of a double asteroid.

Menoetius is the smaller component ( moon ) of the double asteroid system of the L 5 -Jupiter Trojan (617) Patroclus . Its mean diameter is around 113 kilometers, making it only 7.7% smaller than the mother asteroid .

Discovery and naming

Menoetius was born on September 22, 2001 by William J. Merline, Laird M. Close, N. Siegler, D. Potter, Clark R. Chapman, Christophe Dumas, François Menard and David C. Slater with the 8.1-meter Gemini North Telescope discovered on Mauna Kea in Hawaii . It was the first moon to be discovered by a Trojan. Since the Patroclus system is a double system, the Trabant Skamandrios of the Trojan (624) Hektor can also be regarded as the first discovered Trojan moon. The discovery was announced on October 29, 2001; the moon was given the provisional designation S / 2001 (617) 1 . On February 2, 2006, it was given its official name.

The asteroid is named after Menoitius , the father of Patroclus .

Track properties

Menoetius and Patroclus orbit each other in an almost perfectly circular orbit at a mean distance of 680 kilometers (approx. 11 Patroclus and 12 Menoetius radii) around the common center of gravity . This results in a distance between the two surfaces of about 560 km, assuming that both bodies are round. The path eccentricity is a maximum of 0.02.

Menoetius and Patroclus orbit each other in 4 days, 6 hours and 47 minutes, which corresponds to about 1020 orbits in one Patroclus year (about 11.95 earth years).

Physical Properties

According to more recent studies, unlike most asteroids, the two seem to consist primarily of water ice instead of rock , which suggests that they are formed at a greater distance from the sun . The exceptionally low density of 0.8 g / cm 3 - which is lower than water - is more like a cometary composition. It is possible that many of the Trojan asteroids are planetesimals that were captured during the outer migration of the giant planets in the Lagrangian points of the Jupiter- Sun system 3.9 billion years ago.

exploration

Since their discovery in 2001, Menoetius and Patroclus have been observed several times through terrestrial telescopes. Franck Marchis' group observed the system between November 2004 and May 2005 on the 10-meter Keck telescope with the laser guide star - adaptive optics system. The period of rotation of the system could be determined very precisely. The observations indicated a retrograde rotation and showed no measurable precession .

Template: future / in 5 yearsOn January 4, 2017, NASA decided to deploy the Lucy space probe , which is scheduled to start in October 2021 and initially the L 4 Trojans (3548) Eurybates , (15094) Polymele , (11351) Leucus and (21900 ) between 2027 and 2028 ) Orus should investigate. The probe will then swing-by the Earth to reach Menoetius and Patroclus in March 2033 and explore them at close range.

See also

Web links