11
Feb
2008
Shortly About the Biggest Moons of Jupiter and Their Discovery - Io, Europa, Ganymedes and Callisto
Posted by marko as Astronomy Basics
The giant planet Jupiter has a number of moon orbiting from which four are the biggest ones, namely Io, Europa, Ganymedes and Callisto. Jupiter’s moons are very interesting because they all have differences. This article provides a short introduction to the moons of Jupiter and the history of their discovery.
The smallest moon of Jupiter is Europa, which has a diameter of 3138 kilometers. Europa, which is located 671.000 kilometers away from the planet, is fully covered by ice. When looking at the pictures taken by probes, we can see how Europa has a huge slab of ice on its surface. The ice cover has broken into smaller pieces that collide due to gravitational force of Jupiter.
Io is the nearest moon of Jupiter. It is located 442.000 kilometers from Jupiter and it has a diameter of only 3630 kilometers. Because Io is located so close to Jupiter, the gravitational forces of planet Jupiter continuously strengthen Io, which keeps the volcano of Io active.
The biggest moon of Jupiter is Ganymedes, which probably has a liquid ocean under the icy surface. Just like Europa, Ganymedes is also covered by ice. Callisto is the most distant moon of Jupiter and it was formed about 4.5 billion years ago.
Discovery of the moons of Jupiter
The giant planet Jupiter was discovered by Galileo Galilei back in 1610, and because Galilei found also the four biggest satellites of Jupiter, are they nowadays known as Galilei’s moons. Since Galileo Galilei discovered Jupiter, several important discoveries have been made, such as the discovery of Jupiter’s clouds (by Giovanni Cassini) and the discovery of the red spot (by Heinrich Schwabe). The big red spot is known as a giant storm that has been active as long as Jupiter has been observed.
Until 1955 was observed by using telescopes, but after that also radio telescopes and probes were used. In 1973 Pioneer 10 measured the strong gravitational force of Jupiter, and in 1974 Pioneer 11 took close shots of the red spot and polar areas. In 1979 we were able to see the first sharp images of Jupiter and its moons, which were taken by the two Voyager probes. In 1995 probe Galileo set it orbiting Jupiter, analyzed the atmosphere of the planet and sent the data back on Earth. Probably the most spectacular moment of observing Jupiter was in 1994 when comet Shoemaker-Levy 9 hit planet Jupiter. The comet broke into pieces which had a diameter of about one kilometer. The craters the comet created on the surface of Jupiter can easily be seen from the Earth by using a powerful telescope.
If you enjoyed this post, then make sure you subscribe to our RSS Feed or Email Newsletter.This article was written by Marko Pyhajarvi and its original location is in HomeboyAstronomy.Com astronomy blog. For more great astronomy articles, please visit HomeboyAstronomy.Com! Share This
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John Ackerman
February 12th, 2008 at 5:36 pm
1The Origin of the Galilean Moons
The formation of the Galilean moons is unique in several respects. Only 6,000 years ago there was an enormous impact on Jupiter. A plasma cloud thousands of times the size of Jupiter rebounded, eventually to become the planet Venus. The material which failed to escape the gravity of Jupiter formed the proto-Galilean moons. However, they were not yet complete.
A giant,flaming jet of gases continued shooting into space from the impact crater - whirling around as Jupiter rotated with a period close to one hour. Initially the jet extended beyond the farthest moon, Callisto, and could be seen by humans on Earth with the ‘naked eye.’ The jet, fueled by a continuous nuclear conflagration in the impact crater (Jupiter comprises solid, low density methane gas hydrates, mostly water) lasted almost six millennia, and now is marked by the Great Red Spot. As the planet rotated the material in the jet bathed the proto-moons, supplying their outer layers.
The jet material coalesced into low-density, hydrated, cinder-like bodies as they moved farther from the planet, thus the outer moons show many impact craters. The four moons are so different because the jet died down so slowly, that the closer the moons to the planet, the later date at which they were still heated by the jet. Thus their formation was a unique, two-stage process.
The longevity and intensity of the jet was so great that the rotational period of Jupiter was increased to almost ten hours as a result of the angular momentum expelled. The tail end of this slowing rotation was actually recorded up to around 1930, but is currently misinterpreted as the ‘drift’ of the giant storm (the GRS).
A couple of additional interesting effects of the jet: Many of the hydrated, cinder-like bodies from the jet actually formed the main asteroid belt, as evidenced by the fact that they are magnetized, i.e. they coalesced while still within the magnetic field of Jupiter; those shot toward the the inner solar system cause sunspots as they crash into the Sun, which is nice because they help warm the Earth; and the ones expelled in the forward direction form the Kuiper belt objects.
Perhaps the most amazing thing is that these events were all observed by the first one hundred generations of mankind. Or perhaps even more amazing (mysterious?) is that mankind, science, academia are still completely unaware of all these facts. But the unwillingness of modern academia to acknowledge the recent intrusion of God into the world (catastrophism) was predicted some 1950 years ago:
2 Peter 3:3-7 Knowing this first, that ther shall come in the last days scoffers, walking after their own lusts and saying, Where is the promise of his coming? for since the fathers fell asleep, all things continue as they were from the beginning of the creation. For this they willingly are ignorant of , that by the word of God the heavens were of old, and the earth standing out of the water and in the water: Whereby the world that then was, being overflowed with water perished: But the heavens and the earth, which are now, by the same word are kept in store, reserved unto fire against the day of judgement and perdition of ungodly men.
John Ackerman
firmament-chaos.com
marko
February 18th, 2008 at 10:02 am
2John, thanks for your very interesting comment! It was also the longest comment in this blog ever
Thanks!
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