Reading Practice 26

[1] Aside from being known as the largest planet orbiting our sun, Jupiter attracts a lot of attention for other reasons as well. Namely, the large number of moons orbiting the gas giant. The four most famous moons were initially discovered by the famous astronomer Galileo Galilei, for whom they’re named. Yet, the rest of Jupiter’s moons are named for everything from conquests, gods, lovers, and family. Some are a little larger than small asteroids while the Galilean moons would be considered dwarf planets if they orbited the sun instead of Jupiter. For centuries, the allure of the ordered chaos of Jupiter’s moons has drawn the eyes of astronomers. Jupiter’s moons have captivated scientists since their discovery, due to their mysterious origin, and because of their diverse characteristics.

 

[2] The first confirmed observation of Jupiter’s moons was by Galileo Galilei in 1609. Piqued by what he had sighted, by March 1610 Galileo employed the use of a 30x magnification telescope to actually see Jupiter’s four largest moons, thus named Galilean moons. The Galilean moons were the first objects discovered in our solar system not to orbit the Sun. Those first four moons, Ganymede, Callisto, Io, and Europa would remain alone among discovered moons until 1892 when E.E. Barnard discovered Amalthea. Nevertheless, the turn of the century brought on a spate of technological developments with telescopes and telescopic photography leading to the discovery of 13 moons in total by 1979. In 1979 the Voyager space probes launched by the United States reached Jupiter and began documenting even more discoveries. As a result in the acceleration of discovery of Jupiter’s moons there are 67 confirmed moons that have been discovered orbiting Jupiter, 17 of which have yet to be named.

 

[3] Scientists believe that early in Jupiter’s history, more moons of mass and size similar to the Galilean moons may have orbited Jupiter. These early satellites formed from a circumplanetary disk, with varieties of accreting gas and solid debris, similar to a protoplanetary disk. As a result of the existence of this disk, scientists suggest that there have been multiple generations of large moons over time. On the other hand, with each ‘generation’ of moon the disk became thinner, eventually reaching the point where the current generation of large moons, the Galilean moons, are able to be protected by an orbital resonance. The other types of Jupiter’s moons most likely originated from passing asteroids that were captured into orbit. Clusters of these small moons are most likely remnants of asteroids that broke up during the stress of capture or collided with other small moons. In summary, Jupiter casts a large orbital shadow and thus has attracted many moons through various means over the milennia.

 

[4] The characteristics of the moons are as diverse as the ways they came to orbit Jupiter themselves. The largest of Jupiter’s moons is actually even larger than Mercury and each of the Galilean moons are over 3,100 kilometers in diameter. In comparison, the remainder of Jupiter’s smaller moons do not exceed 250 kilometers in diameter. Most of the small moons barely exceed 5 kilometers. Most moons orbit Jupiter faster than Jupiter spins on its axis. On the other hand, the longest orbital period of one of Jupiter’s moons is approximately three Earth years. The shapes of the orbits range from highly eccentric and elliptical to near-perfect circles. Also, a handful of moons even orbit in the opposite direction of Jupiter’s rotation. Consequently, Jupiter’s moons are truly a diverse group of orbital bodies.

 

[5] Jupiter’s 67 moons far outnumber that of any other planet in our solar system. Their discovery as the first objects not orbiting the Sun or Earth captured the imagination of astronomers, and sparked the discovery of 63 other orbiting moons. Although they come in different sizes, with different orbits, and from different origins, Jupiter’s moons provide a small example of how complex forces of gravity work, interact, and conflict with each other as the gas giant captured passing asteroids. As a result, as scientists have come to better understand Jupiter and its moons, they have gained a further understanding of the workings of our own solar system. The rich knowledge gained from observation of Jupiter’s moons has tantalized and intrigued the scientific community and promises future insights into the workings of celestial bodies.