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 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 slightly less than one-thousandth t ...

. The moon was discovered on 5 February 2003 by a team of astronomers 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 ...

and

David C. Jewitt David Clifford Jewitt (born 1958) is a British-American astronomer who studies the Solar System, especially its minor bodies. He is based at the University of California, Los Angeles, where he is a Member of the Institute for Geophysics and Pl ...

, and was later announced on 4 March 2003. It was initially thought to be Jupiter's outermost known moon until recovery observations disproved this in 2020. is about in diameter, and orbits Jupiter at an average distance of about 20,600,000

kilometers The kilometre ( SI symbol: km; or ), spelt kilometer in American English, is a unit of length in the International System of Units (SI), equal to one thousand metres (kilo- being the SI prefix for ). It is now the measurement unit used for ex ...

() in roughly 600 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 reference plane and the orbital plane or axis of direction of the orbiting object. For a satellite orbiting the Eart ...

of around 149° 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 agains ...

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-Centre (geometry), center, in geometry * Eccentricity (g ...

of 0.28. The moon was initially assumed to be part of the

Pasiphae group The Pasiphae group is a group of retrograde irregular satellites of Jupiter that follow similar orbits to Pasiphae and are thought to have a common origin. Their semi-major axes (distances from Jupiter) range between 22.8 and 24.1 million km (th ...

, but is now known to be part of the Ananke group after it was recovered in 2020.MPEC 2003-E11: ''S/2003 J 1, 2003 J 2, 2003 J 3, 2003 J 4, 2003 J 5, 2003 J 6, 2003 J 7''
2003 March 4 (discovery and ephemeris) 2003 J 2 CFHT 2003-04-30

The moon was considered

lost Lost may refer to getting lost, or to: Geography *Lost, Aberdeenshire, a hamlet in Scotland * Lake Okeechobee Scenic Trail, or LOST, a hiking and cycling trail in Florida, US History *Abbreviation of lost work, any work which is known to have bee ...

until 2020, when it was recovered by Sheppard and independently by amateur astronomer Kai Ly. The recovery of the moon was announced by the Minor Planet Center on 26 January 2021.

References

{{DEFAULTSORT:S 2003 J 2 Moons of Jupiter Irregular satellites 20030305 Ananke group Discoveries by Scott S. Sheppard Moons with a retrograde orbit