Ice Worlds Introductions

Welcome to the realm of the ultra frozen. You have looked at the inner planets that are composed of rock and metal, then outward to the giant gas planets. Beyond Neptune lies the realm of ice worlds. The term "world" hardly befits these objects for they are all smaller than our moon. The largest member of this group is Pluto with its companion moon Charon. Pluto was discovered in 1930 and became the ninth planet. All seemed well with the Astronomy students for now "My Very Educated Mother Just Served Up Nine "Pizzas." Kids and adults alike were content to view Pluto as a planet enshrouded in mystery and unimaginable cold. As our telescopes improved, Pluto seemed less and less like a planet and more like a giant ball of ice. A ground swell arose among the Astronomy community in the early 1990's to downgrade Pluto's status from planet to its more likely kindred comet. Indeed, comets are balls of ice whose constitutions are almost identical to objects like Triton, Pluto, and Charon. Educators worldwide thought this downgrade might be justifiable, based on the geologic evidence of Pluto, but more reprehensible would it be to take away the "pizzas" from the acronym. After a series of public and private discussions without and within the International Astronomical Union, Pluto was left with its status of planet, and comets were denied a large member. However, as the late summer 2005, astronomers and students alike may be changing the acronym for a large object has been found orbiting beyond Pluto, and it is bigger than Pluto!

It is this world of ice objects that we will study next in this course. You will look first at the double planet system Pluto and Charon, then "extra solar system planets"and finally at the Comets. Anyone who has witnessed Comet Hale-Bopp in 1997 or Hyakutake in 1996 saw something unforgettable. I think this section will hold a few surprises for you in terms of how they really move in the sky. You will be able to go to movies in the future and correct the misinterpretation of comet motion by the directors and impress your friends with your vast trove of knowledge.

Please go to Pluto first, to complete the planetary study, the move the "new planets", and on toward Comets. From there you will move to Asteroids, rocky objects that occupy parts of the inner Solar System, and your tour of our Sun's family will be complete.



Other Planets?



10th Planet?


Back to Planet Introduction, or to the Syllabus.

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