Belinda (moon)

Belinda
	Belinda viewed by Voyager 2 in 1986
Discovery
Discovered by	Stephen P. Synnott / Voyager 2
Discovery date	January 13, 1986
Designations
Designation	Uranus XIV
Pronunciation	/bəˈlɪndə/
Adjectives	Belindian
Orbital characteristics
Semi-major axis	75 255.613 ± 0.057 km
Eccentricity	0.00007 ± 0.000073
Orbital period (sidereal)	0.623527470 ± 0.000000017 d
Inclination	0.03063 ± 0.028° (to Uranus' equator)
Satellite of	Uranus
Physical characteristics
Dimensions	128 × 64 × 64 km
Surface area	~22000 km2
Volume	~270000 km3
Mass	~(1.4–2.3)×1017 kg
Mean density	0.5–0.84 g/cm3
Surface gravity	~0.002–0.015 m/s2
Escape velocity	~0.017–0.031 km/s
Synodic rotation period	synchronous
Axial tilt	zero
Albedo	0.08 ± 0.01
Temperature	~64 K
	^ Only two dimensions are known; the third dimension has been assumed to equal the smaller known dimension. ;

Belinda is an inner satellite of the planet Uranus. Belinda was discovered from the images taken by Voyager 2 on 13 January 1986 and was given the temporary designation S/1986 U 5.^[10] It is named after the heroine of Alexander Pope's The Rape of the Lock. It is also designated Uranus XIV.^[11]

Belinda belongs to the Portia group of satellites, which also includes Bianca, Cressida, Desdemona, Portia, Juliet, Cupid, Rosalind and Perdita.^[9] These satellites have similar orbits and photometric properties.^[9] Other than its orbit,^[2] size of 128 × 64 km^[3] and geometric albedo of 0.08^[9] virtually nothing is known about it.

The Voyager 2 images show Belinda as an elongated object with its major axis pointing towards Uranus. The moon is very elongated, with its short axis 0.5 ± 0.1 times the long axis.^[3] Its surface is grey in color.^[3]

Belinda is in a stable 44:43 mean-motion resonance with Perdita, and from this its mass has been determined to be roughly 26 times that of Perdita.^[4]

The inner moon system is unstable over timescales of several millions of years. Belinda and Cupid will probably be the first pair of moons to collide, in 100,000 to 10 million years' time depending on the densities of the Portia-group satellites, due to resonant interactions with the much smaller Cupid.^[8]

Notes

^ ^a ^b ^c Calculated on the basis of other parameters.
^ Volume derived from the long axis A, the medium axis B and the short axis C: ${\frac {\pi }{6}}ABC$
^ It is known that Belinda is 26 times the mass of Perdita.^[4] Perdita has a mean radius of 13.3±0.7 km^[7] and a density at maximum of 0.9 g/cm³,^[6] meaning its mass is at maximum 8.87×10¹⁵ kg, which makes Belinda's mass at maximum 2.3×10¹⁷ kg.
^ Maximum density obtained from the calculated maximum mass and the presupposed volume of ~270000 km³.
^ Surface gravity derived from the mass m, the gravitational constant G and the radius r: ${\frac {Gm}{r^{2}}}$
^ Escape velocity derived from the mass m, the gravitational constant G and the radius r: ${\sqrt {\frac {2Gm}{r}}}$