Praxidike , also known as , is a retrograde

irregular satellite In astronomy, an irregular moon, irregular satellite or irregular natural satellite is a natural satellite following a distant, inclined, and often eccentric and retrograde orbit. They have been captured by their parent planet, unlike regular s ...

Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but ...

. It was discovered by a team of

astronomer An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the scope of Earth. They observe astronomical objects such as stars, planets, natural satellite, moons, comets and galaxy, g ...

s from the

University of Hawaii A university () is an institution of higher (or tertiary) education and research which awards academic degrees in several academic disciplines. Universities typically offer both undergraduate and postgraduate programs. In the United States, th ...

led by

Scott S. Sheppard Scott Sander Sheppard (born 1977) is an American astronomer and a discoverer of numerous moons, comets and minor planets in the outer Solar System. He is an astronomer in the Department of Terrestrial Magnetism at the Carnegie Institution for Scie ...

in 2000,MPEC 2001-A29: ''S/2000 J 7, S/2000 J 8, S/2000 J 9, S/2000 J 10, S/2000 J 11''
January 15, 2001 (discovery and ephemeris) and given the temporary designation . It was named in August 2003 after

Praxidike In Greek mythology, Praxidice (Ancient Greek: Πραξιδίκη, ) may refer to the following characters: * Praxidice, goddess of judicial punishment and the exactor of vengeance, which were two closely allied concepts in the classical Greek ...

,IAUC 7998: ''Satellites of Jupiter''
2002 October 22 (naming the moon) the

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

goddess A goddess is a female deity. In many known cultures, goddesses are often linked with literal or metaphorical pregnancy or imagined feminine roles associated with how women and girls are perceived or expected to behave. This includes themes of s ...

punishment Punishment, commonly, is the imposition of an undesirable or unpleasant outcome upon a group or individual, meted out by an authority—in contexts ranging from child discipline to criminal law—as a response and deterrent to a particular acti ...

Orbit

Praxidike

orbit In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such as a p ...

s Jupiter at an average distance of 20,824,000 km in 609.25 days, at an

inclination Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a Plane of reference, reference plane and the orbital plane or Axis of rotation, axis of direction of the orbiting object ...

of 144° to the

ecliptic The ecliptic or ecliptic plane is the orbital plane of the Earth around the Sun. From the perspective of an observer on Earth, the Sun's movement around the celestial sphere over the course of a year traces out a path along the ecliptic again ...

(143° to Jupiter's

equator The equator is a circle of latitude, about in circumference, that divides Earth into the Northern and Southern hemispheres. It is an imaginary line located at 0 degrees latitude, halfway between the North and South poles. The term can als ...

), in a retrograde direction and with an

eccentricity Eccentricity or eccentric may refer to: * Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal" Mathematics, science and technology Mathematics * Off-center, in geometry * Eccentricity (graph theory) of a v ...

of 0.1840. Praxidike belongs to the

Ananke group The Ananke group is a group of retrograde irregular satellites of Jupiter that follow similar orbits to Ananke and are thought to have a common origin. Their semi-major axes (distances from Jupiter) range between 19.3 and 22.7 Gm, their orbital ...

, believed to be the remnants of a break-up of a captured heliocentric asteroid.Sheppard, S. S., Jewitt, D. C.
''An Abundant Population of Small Irregular Satellites Around Jupiter''
, Nature, Vol. 423 (May 2003), pp. 261-263 Nesvorný, D.; Alvarellos, J. L. A.; Dones, L.; and Levison, H. F.
''Orbital and Collisional Evolution of the Irregular Satellites''
The Astronomical Journal, Vol. 126 (2003), pp. 398–429 With an estimated diameter of 7 km, Praxidike is the second largest member of the group after Ananke itself (assumed albedo of 0.04).Sheppard, S. S.; Jewitt, D. C.; Porco, C.;
''Jupiter's Outer Satellites and Trojans''
, in ''Jupiter: The Planet, Satellites and Magnetosphere,'' edited by Fran Bagenal, Timothy E. Dowling, and William B. McKinnon, Cambridge Planetary Science, Vol. 1, Cambridge, UK: Cambridge University Press, , 2004, pp. 263-280

Characteristics

The satellite appears grey ( colour indices B-V=0.77, R-V= 0.34), typical of

C-type asteroid C-type (carbonaceous) asteroids are the most common variety, forming around 75% of known asteroids. They are volatile-rich and distinguished by a very low albedo because their composition includes a large amount of carbon, in addition to rocks ...

s. Grav, T.; Holman, M. J.; Gladman, B. J.; Aksnes, K.
''Photometric Survey of the Irregular Satellites''
Icarus, Vol. 166 (2003), pp. 33-45

References

* Ephemeri

* Mean orbital parameter
NASA JPL

External links

{{DEFAULTSORT:Praxidike (Moon) Ananke group Moons of Jupiter Irregular satellites Discoveries by Scott S. Sheppard 20001123 Moons with a retrograde orbit