Enkelad (mjesec)

Enkelad (Enceladus) je prirodni Saturnov satelit kojeg je 1789. otkrio astronom William Herschel. Ime je dobio po gigantu Enkeladu iz starogrčke mitologije. Ovaj satelit ima drugo ime Saturn II.

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Enkelad

Enceladus snimljen orbiterom Cassini, oktobar 2015.[a]
Discovery
Discovered by	William Herschel
Designations
Designation	Saturn II
Imenovan po	Ἐγκέλαδος Egkelados
Adjectives	Enceladean /ɛnsəˈleɪdiən/[1][2]
Orbital characteristics
Semi-major axis	7005237948000000000♠237.948 km[3]
Orbital period (sidereal)	7006137021800000000♠1,370218 d[3]
Inclination	0.009° (to Saturn's equator)[3]
Physical characteristics
Mean radius	7003252100000000000♠252,1±0,2 km[4][5] (7002395000000000000♠0,0395 Earths, 7003145100000000000♠0,1451 Moons)
Surface gravity	1.134 m/s2 (7002116000000000000♠0,0116 g)
Moment of inertia factor	7003330500000000000♠0,3305±0,0025[6]
Escape velocity	2.391 km/s (860.4 km/h)[3]
Synodic rotation period	Sinhrona
Axial tilt	0
Albedo	7003137500000000000♠1,375±0,008 (geometrijski na 550 nm)[7] or 7001810000000000000♠0,81±0,04 (Bond)[8]
Surface temp. min mean max Kelvin[9] 32.9 K 75 K 145 K Celsius −240 °C −198 °C −128 °C
Apparent magnitude	11.7[10]
Atmosphere
Surface pressure	Trace, significant spatial variability[11][12]
Composition by volume	91% vode pare 4% nitrogen 3.2% ugljen-dioksid 1.7% metan[13]

Karakteristike

Enkelad obilazi Saturn svakih 32 h 53 m 7 s, ima prosječni prečnik od 498,9 km i masu od 8,6×10¹⁹ kg. Prosječna gustoća Enkelada iznosi 1,3 g/cm³. Mjerenja obavljena od strane svemirske letjelice Cassini-Huygens ookazala su da je ovaj satelit napravljen većinom od leda, vode i možda male količine kamena i metala.

Početkom 2006. NASA-ina letjelica Cassini snimila je erupcije gejzira na površini, vjerovatno sastavljene i od tekuće vode.

Bilješke

1. Photograph of Enceladus, taken by the narrow-angle camera of the Imaging Science Subsystem (ISS) aboard Cassini, during the spacecraft’s October 28, 2015, flyby. It shows the younger terrain of Sarandib and Diyar Planitia, populated with many grooves (sulci) and depressions (fossae). Older, cratered terrain can be seen towards Enceladus's north pole. The prominent feature visible near the south pole is Cashmere Sulci.