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In gravitationally bound systems, the orbital speed of an astronomical body or object (e.g. planet, moon, artificial satellite, spacecraft, or star) is the speed at which it orbits around either the barycenter (the combined center of mass) or, if one body is much more massive than the other bodies of the system combined, its speed relative to the center of mass of the most massive body.
Jupiter's moons were classified into four groups of four, based on their similar orbital elements. [204] This picture has been complicated by the discovery of numerous small outer moons since 1999. Jupiter's moons are divided into several different groups, although there are two known moons which are not part of any group (Themisto and Valetudo ...
Measurement of the speed of light from the time it takes Io to orbit Jupiter, using eclipses of Io by Jupiter's shadow to precisely measure its orbit. Io is the innermost of the four moons of Jupiter discovered by Galileo in January 1610. Rømer and Cassini refer to it as the "first satellite of Jupiter".
Io (/ ˈ aɪ. oʊ /), or Jupiter I, is the innermost and second-smallest of the four Galilean moons of the planet Jupiter.Slightly larger than Earth's moon, Io is the fourth-largest moon in the Solar System, has the highest density of any moon, the strongest surface gravity of any moon, and the lowest amount of water by atomic ratio of any known astronomical object in the Solar System.
The observed change in the moon's orbital period is caused by the difference in the time it takes light to traverse the shorter or longer distance. Rømer observed this effect for Jupiter's innermost major moon Io and deduced that light takes 22 minutes to cross the diameter of the Earth's orbit. [94]
A relatively small extra delta-v above that needed to accelerate to the escape speed can result in a relatively large speed at infinity. Some orbital manoeuvres make use of this fact. For example, at a place where escape speed is 11.2 km/s, the addition of 0.4 km/s yields a hyperbolic excess speed of 3.02 km/s:
Ganymede's magnetic field is probably created by convection within its core, and influenced by tidal forces from Jupiter's far greater magnetic field. [23] Ganymede has a thin oxygen atmosphere that includes O, O 2, and possibly O 3 . [17] Atomic hydrogen is a minor atmospheric constituent.
Juno in launch configuration. Juno is a NASA space probe orbiting the planet Jupiter.It was built by Lockheed Martin and is operated by NASA 's Jet Propulsion Laboratory.The spacecraft was launched from Cape Canaveral Air Force Station on August 5, 2011 UTC, as part of the New Frontiers program. [6]