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Jupiter XIV - 1979J2


Thebe [THEE-bee] is the fourth known satellite of Jupiter. Thebe was a nymph and the daughter of the river god Asopus. Thebe rotates synchronously around Jupiter. Very little is known about this moon.

Thebe Statistics
 Discovered byStephen Synnott 
 Date of discovery1979 
 Mass (kg)7.77e+17 
 Mass (Earth = 1)1.3002e-07 
 Radius (km)55x45 
 Radius (Earth = 1)8.6234e-03 
 Mean density (gm/cm^3)1.5 
 Mean distance from Jupiter (km)221,895 
 Rotational period (days)0.674536 
 Orbital period (days)0.674536 
 Mean orbital velocity (km/sec)23.93 
 Orbital eccentricity0.0183 
 Orbital inclination (degrees)1.0659 
 Escape velocity (km/sec)0.0434 
 Visual geometric albedo0.05 
 Magnitude (Vo)15.7 

Views of Thebe

Two Galileo Views of Thebe
These two images of the Jovian moon Thebe were taken by Galileo's solid state imaging system in November 1996 and June 1997, respectively. North is approximately up in both cases. Thebe, whose longest dimension is approximately 116 kilometers (72 miles) across, is tidally locked so that the same side of the satellite always points towards Jupiter, similar to how the near side of our own Moon always points toward Earth. In such a tidally locked state, one side of Thebe always points in the direction in which Thebe moves as it orbits about Jupiter. This is called the "leading side" of the moon and is shown at the left. The image on the right emphasizes the side of Thebe that faces away from Jupiter (the "anti-Jupiter" side). Note that there appear to be at least three or four very large impact craters on the satellite -- very large in the sense that each of these craters is roughly comparable in size to the radius of Thebe. (Courtesy NASA/JPL)

Discovery Image
This is one of the discovery images (FDS 16383.54) of Thebe. It was taken by the Voyager 1 spacecraft 4 hours 26 minutes before the closest approach to Jupiter. This image is a wide angle picture taken at a range 4.3x105 kilometers. The dark circular disk is the shadow of Thebe and not the actual planet. Once the shadow images were analyzed, Thebe was located on several other images. (Credit: Calvin J. Hamilton)

This image of Thebe (FDS 16220.56) was taken by the Voyager 1 spacecraft on February 27, 1979. Thebe is the small dark dot above the arrow. (Credit: Calvin J. Hamilton)

Family Portrait of the Small Inner Satellites of Jupiter
These images, taken by Galileo's solid state imaging system between November 1996 and June 1997, provide the first ever "family portrait" of the four small, irregularly shaped moons that orbit Jupiter in the zone between the planet's ring and the larger Galilean satellites. The moons are shown in their correct relative sizes, with north approximately up in all cases. From left to right, arranged in order of increasing distance from Jupiter, are Metis (longest dimension is approximately 60 kilometers or 37 miles across), Adrastea (20 kilometers or 12 miles across), Amalthea (247 kilometers or 154 miles across), and Thebe (116 kilometers or 72 miles across). While Amalthea, the largest of these four tiny moons, was imaged by NASA's two Voyager spacecraft in 1979 with a resolution comparable to what is shown here, the new Galileo observations represent the first time that Metis, Adrastea, and Thebe have been seen as more than points of light. (Courtesy of NASA/JPL)


Synnott, S. P. "1979J2: Discovery of a Previously Unknown Jovian Satellite." Science, Vol 210, 14 November 1980.

Synnott, S. P. "Orbits of the Small Inner Satellites of Jupiter." Icarus 58, 1984.


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Author: Calvin J. Hamilton.