Pasiphaë (moon)

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Pasiphaë
Discovery
Discovered by: P. J. Melotte
Discovery date: January 27, 1908
Orbital characteristics
Periapsis: 16,980,250 km (0.114 AU)
Apoapsis: 31,209,300 km (0.209 AU)
Mean radius of orbit: 24,094,770 km (0.16106 AU)
Orbital circumference: 148,036,100 km (0.990 AU)
Eccentricity: 0.2953
Orbital period: 764.082032 d (2.092 a)
Avg. orbital speed: 2.242 km/s
Max. orbital speed: 3.109 km/s
Min. orbital speed: 1.692 km/s
Inclination: 145.24° (to the ecliptic)
143.04° (to Jupiter's equator)
Satellite of: Jupiter
Physical characteristics
Mean radius: 30 km
Surface area: ~11,300 km²
Volume: ~113,000 km3
Mass: 3.0×1017 kg
Mean density: 2.6 g/cm3
Equatorial surface gravity: ~0.022 m/s2 (0.002 g)
Escape velocity: ~0.036 km/s
Albedo: 0.04
Temperature: ~124 K

Pasiphaë (pə-sif'-ay-ee, IPA: /pəˈsɪfeɪi/; Greek Πασιφάη) is a retrograde irregular satellite of Jupiter. It was discovered in 1908 by Philibert Jacques Melotte and later named after the mythological Pasiphaë, wife of Minos and mother of the Minotaur from Greek legend.[1]

It was first spotted on a plate taken at the Royal Greenwich Observatory on the night of February 28, 1908. Inspection of previous plates found it as far back as January 27. It received the provisional designation 1908 CJ since it was not clear whether it was an asteroid or a moon of Jupiter. The recognition of the latter case came by April 10.[2]

Pasiphaë did not receive its present name until 1975; before then, it was simply known as Jupiter VIII. It was sometimes called "Poseidon".

Contents

[edit] Orbit

Retrograde irregular satellites of Jupiter.
Retrograde irregular satellites of Jupiter.

Pasiphaë orbits Jupiter on a high eccentricity and high inclination retrograde orbit. It gives its name to the Pasiphaë group, irregular retrograde moons orbiting Jupiter at distances ranging between 22.8 and 24.1 million km, and with inclinations ranging between 144.5° and 158.3°. The diagram illustrates its orbit in relation to other retrograde irregular satellites of Jupiter. The eccentricity of selected orbits is represented by the yellow segments (extending from the pericentre to the apocentre). The outermost regular satellite Callisto is located for reference.

Pasiphae is also known to be in a secular resonance with Jupiter (tying the longitude of its perijove with the longitude of perihelion of Jupiter).[3]

[edit] Physical characteristics

With diameter estimated at 58 km Pasiphaë is the largest retrograde and third largest irregular satellite after Himalia and Elara.

Spectroscopical measurements in infrared indicate that Pasiphaë is a spectrally featureless object, consistent with the suspected asteroidal origin of the object. Pasiphaë is believed to be a fragment from a captured asteroid along with other Pasiphaë group satellites.[4][5]

In the visual spectrum the satellite appears grey (colour indices B-V=0.74, R-V=0.38) similar to C-type asteroids.[6]

[edit] See also

[edit] External links

[edit] References

  1. ^ International Astronomical Union Circular #2846
  2. ^ Monthly Notices of the Royal Astronomical Society, 68 (1908), p.373 Discovery note
  3. ^ David Nesvorný, Cristian Beaugé, and Luke Dones Collisional Origin of Families of Irregular Satellites, The Astronomical Journal, 127 (2004), pp. 1768–1783 (pdf).
  4. ^ Brown, Michael (February 2000). "Near-Infrared Spectroscopy of Centaurs and Irregular Satellites". The Astronomical Journal 119: 977–983. Retrieved on 2006-08-05. 
  5. ^ Scott S. Sheppard, David C. Jewitt An abundant population of small irregular satellites around Jupiter, Nature, 423 (May 2003), pp.261-263 (pdf)
  6. ^ Grav, Tommy; Holman, Matthew J.; Gladman, Brett J.; Aksnes, Kaare Photometric survey of the irregular satellites,Icarus, 166,(2003), pp. 33-45. Preprint
  • Ephemeris (IAU)[1]
  • Mean orbital parameters (NASA)[2]


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