AST 111 Lecture Notes - Lecture 28: Tunxis Community College, Voyager 2, Ecliptic
18 Dec 2020
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Document Summary
Uranus- though barely visible to the naked eye, was unknown by the ancients. Plotted on star charts as early as 1690, its slow orbital motion caused it to go unnoticed until sir william herschel discovered it in 1781. The diameter of uranus is hard to determine because its angular size is small and can"t be seen clearly from earth. An improved determination of uranus"s diameter was made in 1977 during an occultation of a star by the planet. An occultation is the passing of one astronomical object in front of another. The light from the distant object is dimmed when the closer object passes in front. Uranus has a diameter 4 times that of earth. It may have a small rocky core, or no core at all. Uranus" atmosphere is similar to jupiter and saturn: mostly hydrogen and helium with some methane.
