Jupiter is the largest planet in the solar system. It was named after the Roman chief god Jupiter. Its diameter of 88,846 miles is 13,948 miles larger than Saturn’s 74,898 mile diameter. Jupiter’s diameter is larger than Earth’s diameter of 7,926 miles by 80,920 miles. Jupiter is the fifth planet from the sun. Mercury, Venus, Earth, and Mars are closer to the sun in that order. Farther away are Saturn, Uranus, Neptune, and Pluto also in that order. Its distance from the sun is 483,682,810 miles compared to 92,955,820 miles for Earth. This makes Jupiter 390,726,990 miles farther from the sun than the Earth.
Jupiter is one of the four planets named the Jovian planets. The other three Jovian planets are Saturn, Neptune, and Uranus. Pluto is the only planet farther from the sun than the Jovian planets. Jupiter’s atmosphere is composed of helium and hydrogen. The Giant Red Spot was discovered in the seventeenth century. The mass of Jupiter is 2.5 times the mass of all the other planets combined. The proportion to its volume, however, is much less. Its density is less than the Earth’s.
There are many more moons than the twelve we thought Jupiter had in the 1960s. A recent estimate was there are 63 moons revolving around Jupiter. Jupiter takes only ten hours to spin on its axis compared to twenty-four hours for the Earth. The escape velocity is 133,200 miles per hour compared to 25,009 miles per hour for Earth. Jupiter’s atmosphere is about 86% hydrogen and 14% helium with traces of other gases.
There are four planet-sized moons circling Jupiter named Ganymede, Europa, Io, and Callisto. They are also known as the Galilean Satellites because they were first seen by Galileo when he invented the telescope in 1610.
Io is volcanically solar system. Callisto is the second largest moon of Jupiter and third largest in the solar system. Europa has a frozen crust, and Callisto’s crust is icy. Twenty-three new moons were discovered in 2003. The outer moons of Jupiter might be asteroids swept in by Jupiter’s atmosphere. Io’s atmosphere has sulphur dioxide. Europa’s has oxygen, Ganymede’s also has oxygen, and Callisto’s has carbon dioxide. The factthat Europa and Ganymede have atmospheres containing oxygen means they have one of the
requirements for the possibility of life existing on the moons. The names of some of the other moons of Jupiter are Almalthea, Himalia, Elara, Pasiphae, Sinope, Lysithea, Carme, Ananke, Leda, Thebe, Adrastea, Metis, and S/2000 J11.
Pioneer 10 was the first man-made satellite to take pictures of Jupiter on December 3, 1973. It was designed to study the magnetic fields, solar wind, dust particles, and atmosphere of Jupiter and some of its satellites. Pioneer 11, one year later on December 4, 1974, studied the magnetic fields, solar wind, dust particles, radio waves, the higher layers of Jupiter’s atmosphere, and the surfaces of some of its moons. Some of Pioneer’s instruments included Helium Vector Magnetometer, Charged Particle Instrument, Cosmic Ray Telescope, Meteroid Detector, AsteroidMeteoroid Experiment, and an Ultraviolet Photometer. Voyager 1 was the first to send back detailed images of the moons of Jupiter. It was launched on September 5, 1977.
The Juno and Europa Astrobiology Lander was launched to Jupiter on August 5, 2011. Juno is planned to arrive at Jupiter in 2016, studying the magnetic field, gravity field, and atmospheric structure of Jupiter. It was named after the goddess in Roman mythology Juno because she was Jupiter’s wife. Since the satellite Juno will take the first pictures of the surface of Jupiter below its clouds, Juno’s ability to see through clouds makes it an excellent choice for a name for the satellite.
The Hubble Telescope takes pictures of Jupiter from time to time. It circles the Earth on a satellite designed to carry
the telescope around the Earth.