Themisto (moon)
| Themisto | |
|---|---|
| Provisional or systematic name | S / 2000 J 1 S / 1975 J 1 |
| Central body | Jupiter |
| Properties of the orbit | |
| Major semi-axis | 7,284,000 km |
| Periapsis | 5,515,400 km |
| Apoapsis | 9,052,600 km |
| eccentricity | 0.2428 |
| Orbit inclination | 43.254 ° |
| Orbital time | 130.02 d |
| Mean orbital velocity | 4.01 km / s |
| Physical Properties | |
| Albedo | 0.04 |
| Apparent brightness | 21.0 likes |
| Medium diameter | 8 kilometers |
| Dimensions | 6.97 × 10 14 kg |
| Medium density | 2.6 g / cm 3 |
| Acceleration of gravity on the surface | ≈ 0 m / s 2 |
| Escape speed | ≈ 0 m / s |
| discovery | |
| Explorer | |
| Date of discovery | September 30, 1975 |
Themisto (also Jupiter XVIII) is one of the smallest known moons on the planet Jupiter .
discovery
Themisto was first discovered on September 30, 1975 by the astronomers Charles Kowal and Elizabeth Roemer and was initially given the provisional designation S / 1975 J 1 . However, not enough observations could be carried out to determine the orbit data exactly, so that the celestial body was initially lost again.
In 2000 discovered Scott S. Sheppard , David C. Jewitt , Yanga R. Fernández and Eugene (Gene) A. Magnier a supposedly new moon by Jupiter, the name / S 2000 J 1 was given. However, it soon turned out that it must be the object discovered in 1975.
In 2002 the moon was officially named after the Nereid Themisto , a lover of Zeus (Latin Jupiter) from Greek mythology .
Orbit data
Themisto orbits Jupiter on an eccentric orbit at an average distance of 7,507,000 km in around 130 days. The orbit has an eccentricity of 0.2420 and, at 43.3 °, is steeply inclined in relation to the local Laplace plane .
Themisto's orbit is unusual in that it moves between the Galilean moons and the moons of the Himalia group .
Physical data
Themisto has an average diameter of only 8 km. Its density is estimated at 2.6 g / cm³, which is why it would have to be composed mainly of silicate rock. Their surface is very dark. The albedo is 0.04, i.e. that is, only 4% of the incident sunlight is reflected.
With an apparent brightness of 21 m , it is extremely faint.
Web links
- IAUC 2845: Probable new Satellite of Jupiter October 3, 1975 (discovery)
- IAUC 7525: S / 1975 J 1 = S / 2000 J 1 November 25, 2000 (rediscovery)
- MPEC 2000-Y16: S / 1975 J 1 = S / 2000 J 1, S / 1999 J 1 December 19, 2000 (orbital elements and ephemeris)
- IAUC 7998: Satellites of Jupiter October 22, 2002 (numbering and naming)
| before | Jupiter moons | after that |
| Callirrhoe | Themisto |
Megaclite |