Astronomy

Jupiter is the fifth planet from the Sun and is the largest one in the solar system. If Jupiter were hollow, more than one thousand Earths could fit inside. It also contains more matter than all of the other planets combined. It has a mass of 1.9 x 10²⁷ kg and is 142,800 kilometers across the equator. Jupiter possesses 16 satellites, four of which - Callisto, Europa, Ganymede and Io - were observed by Galileo as long ago as 1610. There is a ring system, but it is very faint and is totally invisible from the Earth. (The rings were discovered in 1979 by Voyager 1.) The atmosphere is very deep, perhaps comprising the whole planet, and is somewhat like the Sun. It is composed mainly of hydrogen and helium, with small amounts of methane, ammonia, water vapor and other compounds. At great depths within Jupiter, the pressure is so great that the hydrogen atoms are broken up and the electrons are freed so that the resulting atoms consist of bare protons. This produces a state in which the hydrogen becomes metallic.

Colorful latitudinal bands, atmospheric clouds and storms illustrate Jupiter’s dynamic weather systems. The cloud patterns change within hours or days. The Great Red Spot is a complex storm moving in a counter-clockwise direction. At the outer edge, material appears to rotate in four to six days; near the center, motions are small and nearly random in direction. An array of other smaller storms and eddies can be found through out the banded clouds.

Auroral emissions, similar to Earth’s northern lights, were observed in the polar regions of Jupiter. The auroral emissions appear to be related to material from Io that spirals along magnetic field lines to fall into Jupiter’s atmosphere. Cloud-top lightning bolts, similar to superbolts in Earth’s high atmosphere, were also observed.

Jupiter’s Ring

Unlike Saturn’s intricate and complex ring patterns, Jupiter has a single ring that is almost uniform in its structure. It is probably composed of dust particles less than 10 microns in diameter — about the size of cigarette smoke particles. It extends to an outer edge of about 129,000 kilometers from the center of the planet and inward to about 30,000 kilometers. The origin of the ring is probably from micrometeorite bombardment of the tiny moons orbiting within the ring.

Jupiter’s rings and moons exist within an intense radiation belt of electrons and ions trapped in the planet’s magnetic field. These particles and fields comprise the Jovian magnetosphere or magnetic environment, which extends 3 to 7 million kilometers toward the Sun, and stretches in a windsock shape at least as far as Saturn’s orbit - a distance of 750 million kilometers.

Jupiter Statistics

Characteristic	Measurement
Mass (kg)	1.900e+27
Mass (Earth = 1)	3.1794e+02
Equatorial radius (km)	.. 71,492
Equatorial radius (Earth = 1)	1.1209e+01
Mean density (gm/cm^3)	1.33
Mean distance from the Sun (km)	778,330,000
Mean distance from the Sun (Earth = 1)	2028
Rotational period (hours)	9.841
Orbital period (years)	11.8623
Mean orbital velocity (km/sec)	13.07
Orbital eccentricity	0.0483
Tilt of axis	3.13°
Orbital inclination	1.308°
Equatorial surface gravity (m/sec^2)	22.88
Equatorial escape velocity (km/sec)	59.56
Visual geometric albedo	0.52
Magnitude (Vo)	-2.70
Mean cloud temperature	-121°C
Atmospheric pressure (bars)	0.7

Atmospheric Composition	Percent
Hydrogen	90%
Helium	10%

Views of Jupiter

Jupiter

This image was taken by NASA’s Hubble Space Telescope on February 13, 1995. The image provides a detailed look at a unique cluster of three white oval-shaped storms that lie southwest (below and to the left) of Jupiter’s Great Red Spot. The appearance of the clouds, in this image, is considerably different from their appearance only seven months earlier. These features are moving closer together as the Great Red Spot is carried westward by the prevailing winds while the white ovals are swept eastward. The outer two of the white storms formed in the late 1930s. In the centers of these cloud systems the air is rising, carrying fresh ammonia gas upward. New, white ice crystals form when the upwelling gas freezes as it reaches the chilly cloud top level where temperatures are -130°C. The intervening white storm center, the ropy structure to the left of the ovals, and the small brown spot have formed in low pressure cells. The white clouds sit above locations where gas is descending to lower, warmer regions.

Jupiter

This image was taken by the Wide Field/Planetary Camera of the Hubble Telescope. It is a true color composite of the full disk of Jupiter. All features in this image are cloud formations in the Jovian atmosphere, which contain small crystals of frozen ammonia and traces of colorful compounds of carbon, sulfur and phosphorous. This photograph was taken on May 28, 1991.

Nordic Optical Telescope

This image of Jupiter was taken with the 2.6 meter Nordic Optical Telescope, located at La Palma, Canary Islands. It is a good example of the best imagery that can be obtained from earth based telescopes.

Jupiter and Moons

Voyager 1 took this photo of Jupiter and two of its satellites (Io, left, and Europa, right) on Feb. 13, 1979. In this view, Io is about 350,000 kilometers above Jupiter’s Great Red Spot, while Europa is about 600,000 kilometers above Jupiter’s clouds. Jupiter is about 20 million kilometers from the spacecraft at the time of this photo. There is evidence of circular motion in Jupiter’s atmosphere. While the dominant large scale motions are west-to-east, small scale movement includes eddy like circulation within and between the bands.

The Great Red Spot

This dramatic view of Jupiter’s Great Red Spot and its surroundings was obtained by Voyager 1 on Feb. 25, 1979, when the spacecraft was 9.2 million kilometers from Jupiter. Cloud details as small as 160 kilometers across can be seen here. The colorful, wavy cloud pattern to the left of the Red Spot is a region of extraordinarily complex and variable wave motion.

Rings of Jupiter

This image shows the entire equatorial region of Jupiter. It was created from a mosaic of several images. The Great Red Spot is toward the left of the image.

Moons of Jupiter

This image shows to scale Jupiter’s moons Amalthea,
Io, Europa, Ganymede, and Callisto.

Hubble Photo Gallery of the Galilean Satellites

This is a Hubble Space Telescope family portrait of the four largest moons of Jupiter, first observed by the Italian scientist Galileo Galilei nearly four centuries ago. Located approximately 800 million kilometers away, the moons are so small that, in visible light, they appear as fuzzy disks in the largest ground-based telescopes. Hubble can resolve surface details seen previously only by the Voyager spacecraft in the early 1980’s.
Hubble has charted new volcanic activity on Io’s active surface, found a faint oxygen atmosphere on the moon Europa, and identified ozone on the surface of Ganymede. Hubble ultraviolet observations of Callisto show the presence of fresh ice on the surface that may indicate impacts from micrometeorites and charged particles from Jupiter’s magnetosphere.

Rings of Jupiter

Name	Distance*	Width (km)	Thickness (km)	Mass	Albedo
Halo	100,000	22,800	20,000	?	0.05
Main	122,800	6,400	< 30	1 x 10^13	0.05
Gossamer	129,200	850,000	?	?	0.05

*The distance is measured from the planet center to the start of the ring.

Jupiter’s Moon Summary

Sixteen moons have been discovered orbiting around Jupiter. Most of them are relatively small and seem to have been more likely captured than to have been formed in orbit around Jupiter. Four of the largest moons, Io, Europa, Ganymede and Callisto, are believed to have accreted as part of the process by which Jupiter itself formed. The following table summarizes the radius, mass, distance from the planet center, discoverer and the date of discovery of each of the moons of Jupiter:

Moon	Number	Radius (km)	Mass (kg)	Distance (km)	Discoverer	Year
Metis	XVI	20	9.56e+16	127,969	S. Synnott	1979
Adrastea	XV	12.5 x 10 x 7.5	1.91e+16	128,971	Jewitt-Danielson	1979
Amalthea	V	135 x 84 x 75	7.17e+18	181,300	E. Barnard	1892
Thebe	XIV	55 x 45	7.77e+17	221,895	S. Synnott	1979
Io	I	1,815	8.94e+22	421,600	Marius-Galileo	1610
Europa	II	1,569	4.80e+22	670,900	Marius-Galileo	1610
Ganymede	III	2,631	1.48e+23	1,070,000	Marius-Galileo	1610
Callisto	IV	2,400	1.08e+23	1,883,000	Marius-Galileo	1610
Leda	XIII	8	5.68e+15	11,094,000	C. Kowal	1974
Himalia	VI	93	9.56e+18	11,480,000	C. Perrine	1904
Lysithea	X	18	7.77e+16	11,720,000	S. Nicholson	1938
Elara	VII	38	7.77e+17	11,737,000	C. Perrine	1905
Ananke	XII	15	3.82e+16	21,200,000	S. Nicholson	1951
Carme	XI	20	9.56e+16	22,600,000	S. Nicholson	1938
Pasiphae	VIII	25	1.91e+17	23,500,000	P. Melotte	1908
Sinope	IX	18	7.77e+16	23,700,000	S. Nicholson	1914