Sycorax is the largest retrograde

irregular satellite In astronomy, an irregular moon, irregular satellite or irregular natural satellite is a natural satellite following a distant, inclined, and often eccentric and retrograde orbit. They have been captured by their parent planet, unlike regular s ...

Uranus Uranus is the seventh planet from the Sun. Its name is a reference to the Greek god of the sky, Uranus (mythology), Uranus (Caelus), who, according to Greek mythology, was the great-grandfather of Ares (Mars (mythology), Mars), grandfather ...

. Sycorax was discovered on 6 September 1997 by

Brett J. Gladman Brett James Gladman (born April 19, 1966) is a Canadian astronomer and a full professor at the University of British Columbia's Department of Physics and Astronomy in Vancouver, British Columbia. He holds the Canada Research Chair in planetary as ...

, Philip D. Nicholson,

Joseph A. Burns Joseph Burns is a professor at Cornell University with a dual appointment in the Sibley School of Mechanical and Aerospace Engineering (MAE) and the Astronomy department. His primary area of research is dynamics in planetary sciences. Profession ...

, and John J. Kavelaars using the 200-inch

Hale telescope The Hale Telescope is a , 3.3 reflecting telescope at the Palomar Observatory in San Diego County, California, US, named after astronomer George Ellery Hale. With funding from the Rockefeller Foundation in 1928, he orchestrated the planning, de ...

, together with

Caliban Caliban ( ), son of the witch Sycorax, is an important character in William Shakespeare's play '' The Tempest''. His character is one of the few Shakespearean figures to take on a life of its own "outside" Shakespeare's own work: as Russell H ...

, and given the temporary designation S/1997 U 2. TheIrregulars URANUS retro

Officially confirmed as Uranus XVII, it was named after Sycorax,

's mother in

William Shakespeare William Shakespeare ( 26 April 1564 – 23 April 1616) was an English playwright, poet and actor. He is widely regarded as the greatest writer in the English language and the world's pre-eminent dramatist. He is often called England's nation ...

's play '' The Tempest''.

Orbit

Sycorax follows a distant orbit, more than 20 times further from Uranus than the furthest regular moon,

Oberon Oberon () is a king of the fairies in medieval and Renaissance literature. He is best known as a character in William Shakespeare's play ''A Midsummer Night's Dream'', in which he is King of the Fairies and spouse of Titania, Queen of the Fair ...

. Its orbit is retrograde, moderately

inclined Incline, inclined, inclining, or inclination may refer to: *Grade (slope), the tilt, steepness, or angle from horizontal of a topographic feature (hillside, meadow, etc.) or constructed element (road, railway, field, etc.) *Slope, the tilt, steepn ...

and

eccentric Eccentricity or eccentric may refer to: * Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal" Mathematics, science and technology Mathematics * Off-center, in geometry * Eccentricity (graph theory) of a v ...

. The orbital parameters suggest that it may belong, together with Setebos and

Prospero Prospero ( ) is a fictional character and the protagonist of William Shakespeare's play '' The Tempest''. Prospero is the rightful Duke of Milan, whose usurping brother, Antonio, had put him (with his three-year-old daughter, Miranda) to sea ...

, to the same dynamic cluster, suggesting common origin. The diagram illustrates the orbital parameters of the retrograde

s of Uranus (in polar co-ordinates) with the eccentricity of the orbits represented by the segments extending from the

pericentre An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary (astronomy), primary body. For example, the apsides of the Earth are called the aphelion and perihelion. General description There are two ...

to the apocentre.

Physical characteristics

The diameter of Sycorax is estimated at 165 km based on the thermal emission data from

Spitzer Spitzer is a surname. Notable people with the surname include: * Andre Spitzer (1945–1972), Israeli fencing coach and victim of the Munich massacre * Bernard Spitzer (1924–2014), American real estate developer and philanthropist, father of Eli ...

and Herschel Space telescopes making it the largest irregular satellite of Uranus, comparable in size with Puck and with Himalia, the biggest irregular satellite of Jupiter. The satellite appears ''light-red'' in the

visible spectrum The visible spectrum is the portion of the electromagnetic spectrum that is visual perception, visible to the human eye. Electromagnetic radiation in this range of wavelengths is called ''visible light'' or simply light. A typical human eye wil ...

( colour indices , , ), redder than Himalia but still less red than most

Kuiper belt The Kuiper belt () is a circumstellar disc in the outer Solar System, extending from the orbit of Neptune at 30 astronomical units (AU) to approximately 50 AU from the Sun. It is similar to the asteroid belt, but is far larger—20 times ...

objects. However, in the

near infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...

, the spectrum turns blue between 0.8 and 1.25 μm and finally becomes neutral at the longer wavelengths. The rotation period of Sycorax is estimated at about 6.9 hours. Rotation causes periodical variations of the visible magnitude with the amplitude of 0.12. The rotation axis of Sycorax is unknown, though measurements of its

light curve In astronomy, a light curve is a graph of light intensity of a celestial object or region as a function of time, typically with the magnitude of light received on the y axis and with time on the x axis. The light is usually in a particular frequ ...

suggest it is being viewed at an near equator-on configuration. In this case, Sycorax may have a north pole

right ascension Right ascension (abbreviated RA; symbol ) is the angular distance of a particular point measured eastward along the celestial equator from the Sun at the March equinox to the (hour circle of the) point in question above the earth. When paired w ...

around 356° and a north pole

declination In astronomy, declination (abbreviated dec; symbol ''δ'') is one of the two angles that locate a point on the celestial sphere in the equatorial coordinate system, the other being hour angle. Declination's angle is measured north or south of the ...

around 45°.

Origin

It is hypothesized that Sycorax is a captured object; it did not form in the accretion disk which existed around Uranus just after its formation. No exact capture mechanism is known, but capturing a moon requires the

dissipation In thermodynamics, dissipation is the result of an irreversible process that takes place in homogeneous thermodynamic systems. In a dissipative process, energy (internal, bulk flow kinetic, or system potential) transforms from an initial form to a ...

of energy. Possible capture processes include gas drag in the

protoplanetary disk A protoplanetary disk is a rotating circumstellar disc of dense gas and dust surrounding a young newly formed star, a T Tauri star, or Herbig Ae/Be star. The protoplanetary disk may also be considered an accretion disk for the star itself, be ...

and many-body interactions and capture during the fast growth of Uranus's mass (so-called ''pull-down'').

References

* * * *

External links

Sycorax Profile
(b
NASA's Solar System Exploration

(by

Scott S. Sheppard Scott Sander Sheppard (born 1977) is an American astronomer and a discoverer of numerous moons, comets and minor planets in the outer Solar System. He is an astronomer in the Department of Terrestrial Magnetism at the Carnegie Institution for Scie ...

)
MPC: Natural Satellites Ephemeris Service
{{DEFAULTSORT:Sycorax (Moon) Moons of Uranus Irregular satellites 19970906 Moons with a retrograde orbit

Orbit

Physical characteristics

Origin

See also

References

External links