Pasiphaë (moon)

Infobox Planet
name = Pasiphaë
bgcolour = #ffc0c0
discovery = yes
discoverer = P. J. Melotte
discovered = January 27, 1908
mean_orbit_radius = 24,094,770 kmcite journal |last=Jacobson |first=R. A. |authorlink=Robert A. Jacobson |title=The Orbits of the Outer Jovian Satellites |journal=Astronomical Journal |year=2000 |volume=120 |pages=2679–2686 |doi=10.1086/316817 |url=http://www.iop.org/EJ/article/1538-3881/120/5/2679/200233.html]
eccentricity = 0.2953
periapsis = 16,980,250 km
apoapsis = 31,209,300 km
period = 764.082032 d (2.092 a)
avg_speed = 2.242 km/s
inclination = 145.24° (to the ecliptic) 143.04° (to Jupiter's equator)
satellite_of = Jupiter
physical_characteristics = yes
mean_radius = 30 km
surface_area = ~11,300 km²
volume = ~113,000 km³
mass = 3.0e|17 kg
density = 2.6 g/cm³ (assumed)
surface_grav = ~0.022 m/s² (0.002 g)
escape_velocity = ~0.036 km/s
albedo = 0.04 (assumed)
single_temperature = ~124 K

Pasiphaë (pron-en|pəˈsɪfə.iː respell|pə|SIF|ə-ee, [ [http://dictionary.reference.com/browse/pasiphae?r=75] ] or as in Greek "Πασιφάη)" is a retrograde irregular satellite of Jupiter. It was discovered in 1908 by Philibert Jacques Melottecite journal |last=Melotte |first=P. J. |title=Note on the Newly Discovered Eighth Satellite of Jupiter, Photographed at the Royal Observatory, Greenwich |journal=Monthly Notices of the Royal Astronomical Society |url=http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1908MNRAS..68..456.&db_key=AST&link_type=ABSTRACT&high=40daf3f6f927275 |volume=68 |issue=6 |year=1908 |pages=456–457 ] cite journal |last=Perrine |first=C. D. |authorlink=Charles D. Perrine |title=Recent Observations of the Moving Object Near Jupiter, Discovered at Greenwich by Mr. J. Melotte |journal=Harvard College Observatory Bulletin |volume=20 |month=June | year=1908 |pages=pp. 184–185 |url=http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1908PASP...20..184M&db_key=AST&link_type=ABSTRACT&high=40daf3f6f927275 ] 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 nowrap|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.cite journal |last=Cowell |first=P. H. |authorlink=Philip Herbert Cowell |title=Note on the Discovery of a Moving Object Near Jupiter |journal=Monthly Notices of the Royal Astronomical Society |volume=68 |year=1908 |pages=p. 373 |url=http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1908MNRAS..68..373.&db_key=AST&link_type=ABSTRACT&high=40daf3f6f927275 ]

Pasiphaë did not receive its present name until 1975 [ [http://cfa-www.harvard.edu/iauc/02800/02846.html IAUC 2846: "Satellites of Jupiter"] 1974 October 7 (naming the moon)] ; before then, it was simply known as nowrap|Jupiter VIII. It was sometimes called "Poseidon"cite book| last=Payne-Gaposchkin|first=Cecilia|coauthors=Katherine Haramundanis|title=Introduction to Astronomy|year=1970|publisher=Prentice-Hall|location=Englewood Cliffs, N.J.|isbn=0-134-78107-4] between 1955 and 1975.

Orbit

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°.Sheppard, S. S.; Jewitt, D. C.; and Porco, C. C.; [http://www.ifa.hawaii.edu/~jewitt/papers/JUPITER/JSP.2003.pdf "Jupiter's Outer Satellites and Trojans"] , in "Jupiter: The Planet, Satellites and Magnetosphere," edited by Fran Bagenal, Timothy E. Dowling, William B. McKinnon, Cambridge Planetary Science, Vol. 1, Cambridge, UK: Cambridge University Press, ISBN 0-521-81808-7, 2004, pp. 263-280] The orbital elements are as of January 2000. 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).cite journal |last=Nesvorný |first=D. |authorlink=David Nesvorný |coauthors=Beaugé, C.; and Dones, L. |title=Collisional Origin of Families of Irregular Satellites |journal=The Astronomical Journal |volume=127 |year=2004 |pages=pp. 1768–1783 |url=http://www.iop.org/EJ/article/1538-3881/127/3/1768/203442.html |doi=10.1086/382099 ]

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. [cite journal |last =Brown |first=M. E. |authorlink=Michael E. Brown |title=Near-Infrared Spectroscopy of Centaurs and Irregular Satellites |journal=The Astronomical Journal |volume=119 |pages =977 |publisher=The American Astronomical Society |year=2000 |doi=10.1086/301202] Sheppard, S. S.; and Jewitt, D. C.; [http://www.ifa.hawaii.edu/~jewitt/papers/JSATS/SJ2003.pdf "An Abundant Population of Small Irregular Satellites Around Jupiter"] , Nature, Vol. 423 (May 2003), pp. 261-263 ]

In the visual spectrum the satellite appears grey (colour indices B-V=0.74, R-V=0.38) similar to C-type asteroids.Grav, T.; Holman, M. J.; Gladman, B. J.; and Aksnes, K.; [http://arxiv.org/abs/astro-ph/0301016 "Photometric Survey of the Irregular Satellites"] , Icarus, Vol. 166 (2003), pp. 33-45]

ee also

*Irregular satellites

References

External links

* [http://solarsystem.nasa.gov/planets/profile.cfm?Object=Jup_Pasiphae Pasiphae Profile] by [http://solarsystem.nasa.gov NASA's Solar System Exploration]
* [http://www.ifa.hawaii.edu/~jewitt/irregulars.html David Jewitt pages]
* [http://www.ifa.hawaii.edu/~sheppard/satellites/urasatdata.html Scott Sheppard pages]
* [http://cfa-www.harvard.edu/iau/NatSats/NaturalSatellites.html IAU-MPC NSES]