Jupiter

Jupiter was the roman version of the Greek god Zeus. King of the Olympus gods and son of Chronos.

The most massive planet in our solar system, with four planet-sized moons and many smaller moons, Jupiter forms a kind of miniature solar system. Jupiter resembles a star in composition. In fact, if it had been about eighty times more massive, it would have become a star rather than a planet.

On January 7, 1610, using his primitive telescope, astronomer Galileo Galilei saw four small 'stars' near Jupiter. He had discovered Jupiter's four largest moons, now called Io, Europa, Ganymede, and Callisto. Collectively, these four moons are known today as the Galilean satellites.

Galileo would be astonished at what we have learned about Jupiter and its moons in the past 30 years. Io is the most volcanically active body in our solar system. Ganymede is the largest planetary moon and is the only moon in the solar system known to have its own magnetic field. A liquid ocean may lie beneath the frozen crust of Europa. Icy oceans may also lie deep beneath the crusts of Callisto and Ganymede. In 2003 alone, astronomers discovered 23 new moons orbiting the giant planet, giving Jupiter a total moon count of 63 - the most in the solar system. The numerous small outer moons may be asteroids captured by the giant planet's gravity.

Jupiter's appearance is a tapestry of beautiful colors and atmospheric features. Most visible clouds are composed of ammonia. Water exists deep below and can sometimes be seen through clear spots in the clouds. The planet's 'stripes' are dark belts and light zones created by strong east-west winds in Jupiter's upper atmosphere. Within these belts and zones are storm systems that have raged for years. The Great Red Spot, a giant spinning storm, has been observed for more than 300 years.

The composition of Jupiter's atmosphere is similar to that of the Sun - mostly hydrogen and helium. Deep in the atmosphere, the pressure and temperature increase, compressing the hydrogen gas into a liquid. At depths about a third of the way down, the hydrogen becomes metallic and electrically conducting. In this metallic layer, Jupiter's powerful magnetic field is generated by electrical currents driven by Jupiter's fast rotation. At the center, the immense pressure may support a solid core of ice-rock about the size of Earth.

Jupiter's enormous magnetic field is nearly 20,000 times as powerful as Earth's. Trapped within Jupiter's magnetosphere (the area in which magnetic field lines encircle the planet from pole to pole) are swarms of charged particles. Jupiter's rings and moons are embedded in an intense radiation belt of electrons and ions trapped in the magnetic field. The jovian magnetosphere, comprising these particles and fields, balloons 1 to 3 million kilometers (600,000 to 2 million miles) toward the Sun and tapers into a windsock-shaped tail extending more than 1 billion kilometers (600 million miles) behind Jupiter as far as Saturn's orbit.

Discovered in 1979 by NASA's Voyager 1 spacecraft, Jupiter's rings were a surprise: a flattened main ring and an inner cloud-like ring, called the halo, are both composed of small, dark particles. A third ring, known as the gossamer ring because of its transparency, is actually three rings of microscopic debris from three small moons: Amalthea, Thebe, and Adrastea. Jupiter's ring system may be formed by dust kicked up as interplanetary meteoroids smash into the giant planet's four small inner moons. The main ring probably comes from the moon Metis. Jupiter's rings are only visible when backlit by the Sun.

In December 1995, NASA's Galileo spacecraft dropped a probe into Jupiter's atmosphere, which collected the first direct measurements of Jupiter's atmosphere. Following the release of the probe, the Galileo spacecraft began a multiyear study of Jupiter and the largest moons. As Galileo began its 29th orbit, the Cassini-Huygens spacecraft was nearing Jupiter for a gravity-assist maneuver on the way to Saturn. The two spacecraft made simultaneous observations of the magnetosphere, solar wind, rings, and Jupiter's auroras.

 

Jupiter facts
Fifth planet from the Sun and first in size
Average distance to the sun	778.5 million km
Equatorial diameter	142,984 km
Equatorial diameter (Earth=1)	11.209
Mass (Earth=1)	318
Mean density	1.3 g/cm³
Axial period	9.8 hours
Axial inclination	3.1°
Orbital period	11.86 years
Orbital inclination	1.3°
Orbital eccentricity	0.048
Gravity at cloud-tops (Earth=1)	2.64
Escape velocity	216,720 km/h
Atmospheric composition	89% H2, 10% He
Mean temperature (cloud tops)	-650°C
Albedo	0.50
Number of moons	69

 

Jupiter moons*
1	Io	25	Erinome	49	Kore
2	Europa	26	Isonoe	50	Herse
3	Ganymede	27	Praxidike	51	Jupiter LI
4	Callisto	28	Autonoe	52	Jupiter LII
5	Amalthea	29	Thyone	53	Philophrosyne
6	Himalia	30	Hermippe	54	Dia
7	Elara	31	Aitne	55	Pandia
8	Pasiphae	32	Eurydome	56	Ersa
9	Sinope	33	Euanthe	57	Eirene
10	Lysithea	34	Euporie	58	Eupheme
11	Carme	35	Orthosie	Provisional names
12	Ananke	36	Sponde	2	S/2003 J2
13	Leda	37	Kale	4	S/2003 J4
14	Thebe	38	Pasithee	6	S/2003 J9
15	Adrastea	39	Hegemone	7	S/2003 J10
16	Metis	40	Mneme	8	S/2003 J12
17	Callirrhoe	41	Aoede	10	S/2003 J16
18	Themisto	42	Thelxinoe	11	S/2003 J18
19	Megaclite	43	Arche	12	S/2003 J19
20	Taygete	44	Kallichore	13	S/2003 J23
21	Chaldene	45	Helike	16	S/2011 J1
22	Harpalyke	46	Carpo	17	S/2011 J2
23	Kalyke	47	Eukelade
24	Iocaste	48	Cyllene

*2016 dats from NASA and JPL

Jupiter Rings
Ring	Distance	Width	Mass
	(km)	(km)	(kg)
Halo	100,000	22,800	?
Main	122,800	6,400	1013
Gossamer interior	129,200	52,200	?
Gossamer exterior	182,000	42,900	?

Information from SSE-JPL-NASA - Wikipedia