With its many moons and rings the Jupiter system is a “miniature solar system”. Jupiter is the mass richest planet in our solar system and in its composition is comparable to a small star. The fact is, that Jupiter if he would have been between 50 and 100 times more massive, it would have become a star more of than a planet.
On 7 January 1610 Galileo Galilei observed while he watched the stars in his garden in Padua Jupiter and was surprised to see 4 little “stars” next to him. He had discovered Jupiter’s four largest moons, known as Io, Europa, Ganymede and Callisto. These are now called the Galilean moons.
Galileo would have been fascinated what we have learned about Jupiter and its moons in the last 30 years. Io is the most volcanically active body in our solar system. Ganymede is the largest moon in the solar system with its own magnetic field. Under the icy crust of Europa a liquid ocean is suspected. A frozen ocean is also suspected under the crust of Callisto. Only in 2003, astronomers discovered 22 new moons orbiting Jupiter. Jupiter has officially 79 moons – the largest number in the solar system. Many of these outer moons are probably captured asteroids.
At first glance, Jupiter appears striped. These marks are caused by dark belts and bright zones, which are formed by the strong east-west winds in Jupiter’s atmosphere. Within these belts and zones, there are storm systems that rage there for years. The Great Red Spot in the southern hemisphere has been there for 100 years, probably much longer, as already a similar phenomenon was described by Galileo 400 years ago. The Great Red Spot is 3 times as large as the diameter of the earth. Jupiter’s core is probably not solid, but consists of a dense viscous fluid. The pressure inside Jupiter is probably 30 million times as great as the pressure on the earth’s surface.
The rotation of Jupiter creates a huge magnetic field. In its magnetic field – the area where the magnetic field lines extend from pole to pole – are caught enough charged particles to make the inner portions of Jupiter’s magnetic field the most deadly radioactive environment of all the planets for both – living things and for technical equipment. The tail of Jupiter’s magnetic field – the area between the planet and the sun- side remote – extends to the orbit of Saturn. Jupiter’s rings and moons are within the high-level radioactive belt of electrons and ions trapped in the magnetic field.
Jupiter´s Rings were discovered in 1979 1 by the American space probe Voyager 1. Surprising was, that a flat main ring and an inner cloud -like ring, called the “yard”, consist both of small dark particles. A third ring, because of his transparency known as “cobwebs Ring” is in reality a creation of 3 rings, which were formed from the smallest debris of 3 small moons Amalthea, Thebe and Adrastea. Jupiter’s ring system was probably formed as inner planetary meteorites crashed on the 4 small inner moons and kicked up dust. The main ring probably arose from material from the innermost moon Metis.
In December 1995, the spacecraft Galileo sent a probe into Jupiter’s atmosphere. The probe was equipped with 6 scientific instruments and the probe survived the pressure and heat for about an hour and collected the first direct measurements of Jupiter’s atmosphere. These were the first data on the chemistry of a gas planet. Then Galileo began a multi-year orbit of Jupiter, where also all 4 large moons were observed from a short distance.
| Discovery date | unknown |
| Semi-major axis | 778 357 717 km = 7.783 x 108 km (5.203 AU) Comparison: 5.203 x Earth |
| Perihelion | 740 509 456 km = 7.405 x 108 km (4.95 AU) Comparison: 4.95 x Earth |
| Aphelion | 816 804 370 km = 8.168 x 108 km (5.46 AU) Comparison: 5.46 x Earth |
| Diameter | 144 984 km = 1.44984 x 105 Comparison: 11.209 x Earth |
| Circumference | 449 197 km = 4.49197 x 105 km |
| Volume | 1 425 500 000 000 000 km3 = 1,4255 x 1015 km3 Comparison: 1316 x Earth |
| Mass | 1 898 700 000 000 000 000 000 000 000 kg = 1.8987 x 1027 kg Comparison: 317.82 x Earth |
| Density | 1.33 g/cm3 Comparison: 0.241 x Earth |
| Surface area | 62 179 600 000 km2 = 6.21796 x 1010 km2 Comparison: 121.9 x Earth |
| Surface gravity | 20.87 m/s2 Comparison: Someone with 100 kg on Earth, would weigh 214 kg on Jupiter. |
| Escape velocity | 214 300 km/h = 59 540 m/s Comparison: 5.33 x Earth |
| Sidereal rotation period | 0.41354 Earth days 9.925 hours |
| Orbital period (Length of a year) |
11.8565 Earth years 4330.6 Earth days |
| Average orbital speed | 47 051 km/h = 13 069.7 m/s Comparison: 0,439 x Earth |
| Eccentricity | 0.04839 Comparison: 2.90 x Earth |
| Inclination | 1.305° |
| Axial tilt | 3.13° Comparison: 0.1334 x Earth |
| Peripheral orbit | 4 774 000 000 km = 4.774 x 109 km Comparison: 5.165 x Earth |
| Minimum/Maximum surface temperature |
-148 °C = 125 K Comparison: The temperature of the Earth is ~ 185/331 K |
| Composition of the atmosphere | Hydrogen (H2), Helium (He) Comparison: The atmosphere of the Earth is mainly composed of N2 and O2. |
Moons:
Jupiter has 79 known moons.