Himalia group

 ( Moons Of Jupiter ) 

The Himalia group is a group of prograde irregular satellites of Jupiter that follow similar to Himalia and are thought to have a common origin.Scott S. Sheppard, David C. Jewitt An abundant population of small irregular satellites around Jupiter, Nature, 423 (May 2003), pp.261-263 (pdf)

The known members of the group are (in order of increasing distance from Jupiter):

largest member and group prototype

Two additional possible satellites discovered by Sheppard in 2017 have been identified to be likely part of the Himalia group, but were too faint ( mag >24) to be tracked and confirmed as satellites.

The International Astronomical Union (IAU) reserves names for moons of Jupiter ending in -a (Led a, Himali a and so on) for the moons in this group to indicate prograde motions of these bodies relative to Jupiter, their gravitationally central object.

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Characteristics and origin The objects in the Himalia group have semimajor axis (distances from Jupiter) in the range of 11.10 and 12.30 gigametre, inclinations between 27.2° and 29.1°, and eccentricities between 0.11 and 0.24. All orbit in a prograde direction. In physical appearance, the group is very homogeneous, all satellites displaying neutral colours (color index B−V = 0.66 and V−R = 0.36) similar to those of . Given the limited dispersion of the orbital parameters and the spectral homogeneity, it has been suggested that the group could be a remnant of the break-up of an asteroid from the Asteroid Belt. The radius of the parent asteroid was probably about 89 km, only slightly larger than that of Himalia, which retains approximately 87% of the mass of the original body. This indicates the asteroid was not heavily disturbed.

Numerical integrations show a high probability of collisions among the members of the prograde group during the lifespan of the Solar System ( e.g. on average 1.5 collisions between Himalia and Elara). In addition, the same simulations have shown fairly high probabilities of collisions between prograde and retrograde satellites (e.g. Pasiphae and Himalia have a 27% probability of collision within 4.5 ). Consequently, it has been suggested that the current group could be a result of a more recent, rich collisional history among the prograde and retrograde satellites as opposed to the single break-up shortly after the planet formation that has been inferred for the Carme group and . David Nesvorný, Cristian Beaugé, and Luke Dones Collisional Origin of Families of Irregular Satellites, The Astronomical Journal, 127 (2004), pp. 1768–1783 (pdf).

Categories: Moons Of Jupiter, Irregular Satellites, Moons With A Prograde Orbit

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