Portia is an

inner satellite In astronomy, an inner moon or inner natural satellite is a natural satellite following a prograde, low-inclination orbit inwards of the large satellites of the parent planet. They are generally thought to have been formed ''in situ'' at the same ...

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 ...

. It was discovered from the images taken by ''

Voyager 2 ''Voyager 2'' is a space probe launched by NASA on August 20, 1977, to study the outer planets and interstellar space beyond the Sun's heliosphere. As a part of the Voyager program, it was launched 16 days before its twin, ''Voyager 1'', on a ...

'' on 3 January 1986, and was given the temporary designation S/1986 U 1. The moon is named after Portia, the heroine of

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 Merchant of Venice ''The Merchant of Venice'' is a play by William Shakespeare, believed to have been written between 1596 and 1598. A merchant in Venice named Antonio defaults on a large loan provided by a Jewish moneylender, Shylock. Although classified as ...

''. It is also designated Uranus XII. Portia is the second-largest inner satellite of Uranus after Puck. The Portian orbit, which lies inside Uranus' synchronous orbital radius, is slowly decaying due to

tidal deceleration Tidal acceleration is an effect of the tidal forces between an orbiting natural satellite (e.g. the Moon) and the primary planet that it orbits (e.g. Earth). The acceleration causes a gradual recession of a satellite in a prograde orbit away from ...

. The moon will one day either break up into a

planetary ring A ring system is a disc or ring, orbiting an astronomical object, that is composed of solid material such as dust and moonlets, and is a common component of satellite systems around giant planets. A ring system around a planet is also known as ...

or hit Uranus. It heads a group of satellites called the Portia Group, which includes

Bianca Bianca is a feminine given name. It means "white" and is an Italian cognate of Blanche. Variants * Blanche: French * Bianca: Italian * Bianka (Polish, Hungarian, Slovak, German, English, French, Icelandic, Finnish, Dutch, Norwegian, Co ...

Cressida Cressida (; also Criseida, Cresseid or Criseyde) is a character who appears in many Medieval and Renaissance retellings of the story of the Trojan War. She is a Trojan woman, the daughter of Calchas, a Greek seer. She falls in love with Troilus, ...

Desdemona Desdemona () is a character in William Shakespeare's play ''Othello'' (c. 1601–1604). Shakespeare's Desdemona is a Venetian beauty who enrages and disappoints her father, a Venetian senator, when she elopes with Othello, a Moorish Venetian ...

Juliet Juliet Capulet () is the female protagonist in William Shakespeare's romantic tragedy ''Romeo and Juliet''. A 13-year-old girl, Juliet is the only daughter of the patriarch of the House of Capulet. She falls in love with the male protagonist R ...

, Rosalind,

Cupid In classical mythology, Cupid (Latin Cupīdō , meaning "passionate desire") is the god of desire, lust, erotic love, attraction and affection. He is often portrayed as the son of the love goddess Venus (mythology), Venus and the god of war Mar ...

Belinda Belinda is a feminine given name of unknown origin, apparently coined from Italian ''bella'', meaning "beautiful". Alternatively it may be derived from the Old High German name ''Betlinde'', which possibly meant "bright serpent" or "bright linde ...

and Perdita. These satellites have similar orbits and photometric properties. Little is known about Portia beyond its size of about 140 km in diameter, orbit, and geometric

albedo Albedo (; ) is the measure of the diffuse reflection of sunlight, solar radiation out of the total solar radiation and measured on a scale from 0, corresponding to a black body that absorbs all incident radiation, to 1, corresponding to a body ...

of about 0.08. In the Voyager 2 images, Portia appears as an elongated object whose major axis points towards Uranus. The ratio of axes of the Portia's

prolate spheroid A spheroid, also known as an ellipsoid of revolution or rotational ellipsoid, is a quadric surface obtained by rotating an ellipse about one of its principal axes; in other words, an ellipsoid with two equal semi-diameters. A spheroid has circu ...

is 0.8 ± 0.1. Its surface is grey in color. Observations with

Hubble Space Telescope The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most versa ...

and large terrestrial telescopes found water ice absorption features in the spectrum of Portia.

Gallery

File:Portia1.jpg, Portia seen on January 23, 1986.

References

Explanatory notes Citations

External links

Portia 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 ...

) {{DEFAULTSORT:Portia (Moon) Moons of Uranus 19860103 Moons with a prograde orbit The Merchant of Venice

Gallery

See also

References

External links