Planetary Satellites

The term planetary satellite refers to any celestial body that orbits around another or a planet and during most nights, one can look into the sky and see our planetary satellite in all of its white, shining glory. Beyond simply being an ornament in the sky, the moon plays a functioning role as a satellite to our planet by influencing tides and ocean levels. Although, our moon is the most important and well known from our perspective, it is not a unique occurrence in the universe, or our solar system for that matter. Moons exist all throughout our solar system and come in two main categories; regular moons and irregular moons. While our moon and many of the major moons in our solar system are regular moons, which means they follow consistent, nearly circular orbit paths, some are not. Irregular moons follow an eccentric, retrograde orbit. The odd paths of irregular satellites are theorized to be a result of past collisions between the moons in asteroids, which makes the paths of irregular moons very hard to predict.

For centuries, astronomers have been aware that there are a variety of moons in our solar system, but until the influence of modern technology, the exact number was unknown. In the 15th century, astronomer Galileo Galilei was noted for the discovery of four satellites around Jupiter. Through the years, additional astronomers added to this count and by the year 1951, it was determined that the exact number of moons in our solar system was 31. The distribution of planetary satellites was as follows: Jupiter had 12 discovered moons, 9 moons surrounded Saturn, Uranus had 5, Neptune 2, Mars 2 and Earth 1. Though this count of satellites in our solar system may seem high to some, scientists would soon discover that the number was actually hugely underestimated. With the launching of the Voyager 1 & 2, scientists were able to obtain images that greatly increased the number of discovered planetary satellites in the solar system; by 1989 the number of moons went from 31 to 60. In recent years, advancements in telescope technology have further increased the number of planetary satellites discovered in our satellites. Many planetary satellite discoveries are made by astute observers of the sky, but it is not until the International Astronomical Union (IAU) confirms the satellites orbit that it is officially identified as a moon. As of June 2011, the number of moons in our solar system has reached a whopping 170, which is an extreme increase from estimates from sixty years ago. The currently accepted moon distribution in our solar system is: Mercury 0, Venus 0, Earth 1, Mars 2, Jupiter 65, Saturn 62, Uranus 27, and Neptune 13, along with 5 moons being distributed between the dwarf planets of Pluto, Eris and Haumea. The most striking figures are undoubtedly Jupiter and Saturn who both have more moons individually than was expected for the entire solar system.

Planetary satellites come in a variety of sizes, shapes and have many features that would seem alien when compared to our moon. Some moons have been through cataclysmic cosmic collisions and have obscure shapes, while others have spewing volcanoes and an abundance of hot gases. Regardless, it is no known that between irregular and regular moons that are 170 in our solar system; a number that can easily increase as more discoveries are made.




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