Prospero (moon)

Matthew J. Holman, John J. Kavelaars, Brett J. Gladman, Jean -Marc Petit, Hans Scholl

Prospero (also Uranus XVIII) is the twenty-fifth of the 27 known and the seventh of the outer irregular satellites of the planet Uranus. He is one of the smaller natural satellite of the planet.

Discovery and designation

Prospero was discovered on July 18, 1999 a team of astronomers Matthew J. Holman, John J. Kavelaars, Brett J. Gladman, Jean -Marc Petit and Hans Scholl on photographic images together with the Uranian moons Stephano and Setebos. The images were taken by the 3.6-meter Canada -France - Hawaii Telescope on Mauna Kea in Hawaii (USA). The discovery was announced on 4 September 1999; the moon first received the provisional designation S/1999 U 3

On 21 August 2000 the moon will then receive the official name Prospero, like all irregular moons of Uranus except Margaret, after a figure in William Shakespeare's The Tempest. The magician Prospero was the rightful Duke of Milan. His brother Antonio pulled with the help of Alonso, King of Naples, the power in the duchy itself. Prospero was forced to flee with his daughter Miranda on an island in the Mediterranean, where he perfected his magical powers to recover his duchy. He caused that Alonso and Antonio suffered shipwreck on his island. He eventually reconciled with them and was again master of his duchy.

So far, all the moons of Uranus are named after characters from Shakespeare or Alexander Pope. The first four moons discovered Uranus ( Oberon, Titania, Ariel, Umbriel ) were proposed by John Herschel, the son of Uranus discoverer William Herschel, named. Later, the tradition of naming was retained.

The provisional designation S/1999 U 3 corresponds to the classification of the International Astronomical Union ( IAU).

Web properties

Prospero Uranus rotates on a retrograde, relatively highly elliptical orbit 10834570-21489900 km from its center ( Large semi-major axis 16,162,240 km or 632.350 Uranus radii ), or about 16.1367 million km on whose cloud tops. The orbital eccentricity of 0.3296367, the orbit is inclined 146.01704 ° to the ecliptic. Prospero times as far, nearly 28 of Uranus as the outermost regular moon Oberon.

Due to the large distance to Uranus and gravitational disturbances caused by the sun and other factors, the orbital parameters are thus possibly variable; the moon could perhaps get ( back ) into a heliocentric orbit. The eccentricity is therefore 0.4431 to 0.4448, the orbital inclination ( with respect to the ecliptic ) between 151.83 ° and 152.0 °, and the Large semi-major axis between 16,2430 und 16.2768 million kilometers indicated.

Prospero is a member of Sycorax group, a subgroup of the irregular moons with very high eccentricity and high orbital inclinations of 140 to 170 °, which also Sycorax, and Setebos Ferdinand belong.

The orbit of the next inner moon Margaret is on average about 1.74 million kilometers away from Prospero's orbit, the distance of the path of the next outer moon Setebos is on average about 1.26 million kilometers.

Prospero revolves around Uranus in 1962 days 22 hours and 48 minutes or about 5,374 Earth years. The orbital period is also specified with 1977.0 and 1978.37 days. Prospero needed for one orbit around Uranus so about 9 months longer than the dwarf planet Ceres around the sun.

Physical Properties

Prospero has a diameter estimated at 50 km ( according to other sources 30 km), based on the assumed for him albedo of 4 %, which may be as well as 7%. The surface is thus in any case very dark. Its density is estimated to be between 1.3 and 1.5 g/cm3. So the moon is likely to be composed predominantly of water ice and silicate rock. On its surface, the gravitational acceleration is 0.0063 m/s2, corresponding to about 6 thousand of the earthly. Prospero appears in the spectrum in gray.

Formation

It is believed that Prospero is a captured Kuiper belt object and is not in the accretion disk that formed the Uranus system, created. It is conceivable that the moon of a Kuiper Belt object first became a centaur and was subsequently captured by Uranus. The exact trapping mechanism is not known, but the entrapment of a moon requires the dissipation of energy. The hypotheses range from withdrawal of gas from the protoplanetary disk, interactions within the framework of the multi- body problem and capture by the strongly growing mass of Uranus. The orbital parameters suggest that Prospero belongs to the same group dynamic as Sycorax and Setebos and these moons therefore likely to have a common origin.

Research

Because of the great distance to Uranus and weak brightness of 23.2 like that is 1:7600000 opposite to the central planet, Prospero was 2 1986 not found during the flyby of the Voyager spacecraft. Since the discovery in 1999, Prospero could be observed, while its orbital elements and its brightness can be determined only by ground-based telescopes.

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