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Discovery
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| Discovered by | P. J. Melotte |
| Discovery date | January 27, 1908 |
| Periapsis | 16,980,250 km[1] |
| Apoapsis | 31,209,300 km[1] |
| Mean orbit radius | 24,094,770 km[1] |
| Eccentricity | 0.2953[1] |
| Orbital period | 764.082032 d (2.092 a)[1] |
| Average orbital speed | 2.242 km/s |
| Inclination | 145.24° (to the ecliptic) 143.04° (to Jupiter's equator)[1] |
| Satellite of | Jupiter |
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Physical characteristics
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| Mean radius | 30 km[2] 18? km[3] |
| Surface area | ~11,300 km² |
| Volume | ~113,000 km³ |
| Mass | 3.0×1017 kg |
| Mean density | 2.6 g/cm³ (assumed)[2] |
| Equatorial surface gravity | ~0.022 m/s2 (0.002 g) |
| Escape velocity | ~0.036 km/s |
| Albedo | 0.04 (assumed)[2] 0.10[3] |
| Temperature | ~124 K |
Pasiphaë ( /pəˈsɪfə.iː/ pə-sif-ə-ee;[4] Greek: Πασιφάη) is a retrograde irregular satellite of Jupiter. It was discovered in 1908 by Philibert Jacques Melotte[5][6] and later named after the mythological Pasiphaë, wife of Minos and mother of the Minotaur from Greek legend.
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, as it was not clear whether it was an asteroid or a moon of Jupiter. The recognition of the latter case came by April 10.[7]
Pasiphaë did not receive its present name until 1975;[8] before then, it was simply known as Jupiter VIII. It was sometimes called "Poseidon"[9] between 1955 and 1975.
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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°.[10] The orbital elements are as of January 2000.[1] They are continuously changing due to solar and planetary perturbations. 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).[11]
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.[12][13]
In the visual spectrum the satellite appears grey (colour indices B-V=0.74, R-V=0.38) similar to C-type asteroids.[14]
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