Helike , also known as , is a

moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...

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 ...

. It was discovered 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 ...

in 2003, and given the temporary designation . Helike is about 4 kilometres in diameter, and orbits Jupiter at an average distance of 20.54 million kilometres in 601.402 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 155° 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 ...

(156° to Jupiter's equator), 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-Centre (geometry), center, in geometry * Eccentricity (g ...

of 0.1375. Its average orbital speed is 2.48 km/s. It was named in March 2005 after

Helike Helike (; el, , pronounced , modern ) was an ancient Greek polis (city-state) that was submerged by a tsunami in the winter of 373 BC. It was located in the regional unit of Achaea, northern Peloponnesos, two kilometres (12 stadia) from the ...

, one of the nymphs that nurtured

Zeus Zeus or , , ; grc, Δῐός, ''Diós'', label= genitive Boeotian Aeolic and Laconian grc-dor, Δεύς, Deús ; grc, Δέος, ''Déos'', label= genitive el, Δίας, ''Días'' () is the sky and thunder god in ancient Greek reli ...

(Jupiter) in his infancy on

Crete Crete ( el, Κρήτη, translit=, Modern: , Ancient: ) is the largest and most populous of the Greek islands, the 88th largest island in the world and the fifth largest island in the Mediterranean Sea, after Sicily, Sardinia, Cyprus, ...

. Helike belongs to the Ananke group.

References

{{DEFAULTSORT:Helike (Moon) Ananke group Moons of Jupiter Irregular satellites Discoveries by Scott S. Sheppard Astronomical objects discovered in 2003 Moons with a retrograde orbit