Sycorax (moon)

Brett J. Gladman, Philip D. Nicholson, Joseph A. Burns, John J. Kavelaars

Sycorax (also Uranus XVII) is the twenty-third of the 27 known and the fifth of the outer retrograde irregular moons of the planet Uranus. It is the largest of the irregular natural satellite of the planet.

  • 3.1 surface

Discovery and designation

Sycorax was taken on the night of 6 to 7 September in 1997 by a team of astronomers Philip D. Nicholson, Joseph A. Burns, and John J. Kavelaars on photographic images on the same night as the second- largest known irregular moon Uranus Caliban. The recordings were made by the 5.0 -meter telescope of the Hale Observatory in California (USA). The actual discovery was made by the team member Brett J. Gladman early October, the tracked two moons on the recordings. Sycorax and Caliban were the first discovered irregular satellites of the planet. The discovery was announced on 30 April 1998; the moon was end of October 1997 the provisional designation S/1997 U first 2

In 1999, the moon on the proposal by Brett Gladman, Phil Nicholson, Joseph Burns, JJ Kavelaars, Brian Geoffrey Marsden, Gareth V. Williams and Warren B. Offutt out then get the official name Sycorax, like all irregular moons of Uranus except Margaret, after a figure in William Shakespeare's The Tempest. Sycorax was a witch who had already died before the onset of action. She was banished to the island in the Mediterranean, where she gave birth to Caliban and Prospero was exiled while later. She was responsible for the unjust imprisonment and enslavement of the air spirit Ariel, who was later freed by Prospero.

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/1997 U 2 corresponds to the classification of the International Astronomical Union ( IAU).

Web properties

Orbit

Sycorax Uranus rotates on a retrograde, highly elliptical orbit 5957740-18393380 km from its center ( Large semi-major axis 12,175,560 km or 476.371 Uranus radii ), or about 12.15 million kilometers on whose cloud tops. The orbital eccentricity of 0.5106803, the orbit is inclined 152.49571 ° to the ecliptic. Sycorax is almost 21 times as far from 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. According to calculations by a Russian astronomer, the orbital inclination has changed by about 7 ° and the eccentricity of about 10%. The eccentricity is therefore 0.5219 to 0.5224, the orbital inclination ( with respect to the ecliptic ) between 152.456 and 159.420 ° ° and the Great semi-major axis specified with 12.1794 million km. Due to the high eccentricity Sycorax Uranus comes closer than the three more inner moons circling Caliban, Stephano and Trinculo in their periapsis.

Sycorax is the largest and eponymous member of the Sycorax group, a subgroup of the irregular moons with very high eccentricity and high orbital inclinations of 140 to 170 °, which also Prospero, Setebos and Ferdinand belong. However, Sycorax has a much redder color than the other moons of the group, the more likely to have a gray color.

The orbit of the next inner moon Trinculo is removed an average of about 3,670,000 km from the orbit of Sycorax, the distance of the path of the next outer moon Margaret averages about 2,240,000 km.

Sycorax revolves around Uranus in 1283 days 11 hours and 31 minutes or about 3,514 Earth years. The orbital period is also specified with 1288.28 and 1288.38 days. Sycorax requires almost exactly as long as the asteroid Vesta to the sun for one orbit around Uranus.

Rotation

The light curve of Sycorax has a rotation of between 3 hours and 42 minutes ( 3.7 hours ) and 4 hours and 6 minutes ( 4.1 hours ) out.

Physical Properties

Sycorax has a diameter estimated at 150 km ( according to other sources 190 km), based on the assumed for them albedo of 4 %, which may be as well as 7%. The surface is thus in any case very dark. Their 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 acceleration due to gravity is 0.040 m/s2, this represents approximately 0.4 % of the earthly.

Surface

Over the surface of Sycorax is as good as nothing is known. According to some reports, it has a reddish appearance, red as the Jupiter moon Himalia or the sun, but less red than most Kuiper Belt objects. Sycorax is perhaps a little less red than the second largest irregular moon Uranus Caliban, suggesting a different origin. They generally similar to that of the trans-Neptunian objects, such as the coloring ago Pluto and others, reflected in contrast to these, however, less light. In the near infrared spectrum between wavelengths of 0.8 to 1.25 meters and blue at longer wavelengths is ultimately neutral.

Formation

It is believed that Sycorax 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 Sycorax belongs to the same group as dynamic Setebos and Prospero and these moons therefore likely to have a common origin.

Research

Because of the great distance to Uranus and weak brightness of 20.8 like that is 1:1300000 opposite to the central planet Sycorax was 2 1986 not found during the flyby of the Voyager spacecraft. Since the discovery in 1997 Sycorax could only be observed by ground-based telescopes, while their orbital elements and their brightness can be determined.

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