Perdita (moon)

Perdita is a closer moon to Uranus. Perdita's discovery was not simple. The first pictures of Perdita were taken by the Voyager 2 spacecraft in 1986, but it was not seen on the photographs for more than ten years. In 1999, the moon was noticed and reported.^[1][4]

Perdita

Discovery
Discovered by	Erich Karkoschka / Voyager 2
Discovery date	May 18, 1999 (in images dating back to January 18, 1986)
Orbital characteristics
Mean orbit radius	76,417 ± 1 km[1]
Eccentricity	0.0012 ± 0.0005[1]
Orbital period	0.638021 ± 0.000013 d[1]
Inclination	0.0 ± 0.3° (to Uranus' equator)[1]
Satellite of	Uranus
Physical characteristics
Dimensions	30 × 30 × 30 km[1]
Mean radius	15 ± 3 km[1]
Surface area	~2,800 km²[2]
Volume	~14,000 km³[2]
Mass	~0.18×1017 kg[2]
Mean density	~1.3 g/cm³ assumed
Surface gravity	~0.0047 m/s2[2]
Escape velocity	~0.011 km/s[2]
Rotation period	synchronous[1]
Axial tilt	zero[1]
Albedo	0.08 ± 0.01[3]
Temperature	~64 K[2]

Because no further pictures could be taken to confirm its existence, in 2001 it was thought to be non-existent.^[5] However, in 2003, pictures taken by the Hubble Space Telescope managed to pick up an object where Perdita was supposed to be. This proved its existence at last.^[6][7]

After its discovery in 1999, Perdita was labelled S/1986 U 10.^[4] she was the daughter of Leontes and Hermione in William Shakespeare's play The Winter's Tale. The moon is also called Uranus XXV.^[8]

Perdita belongs to Portia Group of moons, which also includes Bianca, Cressida, Desdemona, Portia, Juliet, Cupid, Rosalind and Belinda.^[3] These moons have similar orbits and photometric properties.^[3] Unfortunately, other than its orbit,^[1][6] radius of 15 km,^[1] and geometric albedo of 0.08,^[3] almost nothing is known about it.