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
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.
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