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Related to satellite: Satellite radio, Satellite phone


1. a celestial body orbiting around a planet or star
2. a man-made device orbiting around the earth, moon, or another planet transmitting to earth scientific information or used for communication
3. a country or political unit under the domination of a foreign power
4. a subordinate area or community that is dependent upon a larger adjacent town or city




(religion, spiritualism, and occult)

A satellite is any body that orbits another body. The body being orbited is referred to as the primary. The most familiar examples of satellites are the Moon, a satellite of Earth, and Earth, a satellite of the Sun. This term was originally used to refer to attendants of important people. It was first applied to celestial bodies by Johannes Kepler, who used the term satellite to refer to the moons of Jupiter.



in astronomy, a body of the solar system that revolves about a planet under the action of the planet’s gravitational attraction. The four brightest satellites of Jupiter—lo, Europa, Ganymede, and Callisto—were, aside from the earth’s moon, the first satellites to be observed. They were discovered by Galileo in 1610. By 1975, 33 satellites of the planets were known: one, the moon, of the earth, two of Mars, 13 of Jupiter, ten of Saturn, five of Uranus, and two of Neptune.

Satellites travel within the gravitational fields of the planets in orbits that differ only slightly in shape from ellipses. The deviations of the actual orbits from elliptical orbits are a result of perturbations caused by the sun’s attraction and by the deviation of the planets’ shapes from a spherical shape. The perturbations that satellites introduce into each other’s orbits can be used to determine the masses of the satellites. The orbital motion of most satellites is direct. In other words, the satellite revolves about the planet in the same direction that the planet revolves about the sun—that is, in a counterclockwise direction when viewed from the north pole of the ecliptic. The only satellites to have retrograde orbits are the satellites VIII, IX, XI, and XII of Jupiter, Saturn’s satellite Phoebe, Uranus’ satellites, and Neptune’s satellite Triton. Table 1 gives the principal data on the known satellites of the planets.

The satellites Phobos and Deimos of Mars are remarkable for their proximity to the planet and their rapid motion. The inner satellite, Phobos, revolves about Mars faster than Mars rotates on its axis, so that an observer on the Martian surface would see the satellite rise in the west and set in the east. Phobos rises and sets twice in a Martian day. Deimos moves across the sky more slowly: more than 2½ days pass between the time the satellite rises above the horizon and the time it sets. Both satellites move almost exactly in the equatorial plane of Mars. In 1972 the Mariner 9 space probe took close photographs of Phobos and Deimos. Both satellites proved to be irregular in shape. Phobos’ dimensions are 27 km × 21 km × 19 km, and those of Deimos are 15 km × 12 km × 11 km; the measurement error here is 0.5–3 km. The geometrical albedo of the Martian satellites does not exceed 0.05—that is, in terms of reflectivity they are comparable to the darkest parts of the lunar maria. Phobos and Deimos are covered with many craters. One crater on Phobos has a diameter of approximately 5.3 km. The craters were undoubtedly formed by impacts.

The four largest satellites of Jupiter—that is, the satellites discovered by Galileo—are comparatively bright objects of the fifth and sixth magnitude. Their orbits are almost circular, and the

Table 1. Satellites of the planets (1975 data)
PlanetSatelliteMean distance from planet (thousands of km)Sidereal period of revolution (days)EccentricityInclination of orbit to planet’s equatorial plane (degrees)Diameter (km)Mass (mass of moon = 1)Year of discovery
 l lo4221.80.0000.03,6400.991610
 I I Europa6713.60.0000.03,1000.641610
 III Ganymede1,0707.20.0010.05,2702.111610
 IV Callisto 1,88016.70.0070.05,0001.321610
 I X23,7007550.28153201914

planes of their orbits approximately coincide with the plane of the planet’s equator. The first determination of the speed of light was made in 1676 on the basis of observations of the eclipses of these satellites. Ganymede and Callisto are larger than the planet Mercury. For each of the four satellites, the period of rotation is the same as the period of revolution about Jupiter. Consequently, each satellite always presents the same side to the planet. A considerable part of the surfaces of Europa and Ganymede is covered with ice. The Pioneer 10 spacecraft discovered in 1973 that Io has a dense atmosphere. Jupiter’s satellite XIII was discovered in October 1974.

Saturn’s satellite Titan is larger than Mercury. Titan has an atmosphere, which, like the atmosphere of Saturn, contains methane and ammonia. The closest satellite to the planet, Janus, was discovered on Dec. 15,1966, when Saturn’s rings were invisible. This satellite is usually concealed in the halo of the brilliant rings.

The orbital planes of the satellites of Uranus are close to the equatorial plane of the planet. The satellites revolve in the same direction as Uranus rotates. Since, however, the equatorial plane of the planet is tilted at an angle of 98° to the plane of the planet’s orbit, Uranus moves with its satellites as if it were lying on its side.

Neptune’s satellite Triton was discovered in 1846, two weeks after the discovery of the planet. Triton is larger in size and greater in mass than the moon. The other satellite, Nereid, has a highly eccentric orbit. As a result, its distance from the planet varies from 1.5 to 9.6 million km.

Most of the names of the satellites were taken from ancient mythology and works of literature. The satellites of Jupiter discovered by Galileo are also designated by the Roman numerals I, II, III, and IV, in order of increasing distance from Jupiter. Jupiter’s remaining satellites, which were discovered later, are designated by Roman numerals in the chronological order of the satellites’ discovery.


What does it mean when you dream about a satellite?

A dream about a satellite is most likely about communication, particularly at a global level. Alternatively, a satellite is something that is trapped by the gravitational pull of another heavenly body.


(aerospace engineering)
A small, solid body moving in an orbit around a planet; the moon is a satellite of earth.
(cell and molecular biology)
A chromosome segment distant from but attached to the rest of the chromosome by an achromatic filament.
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