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A Star is Born
How Planets Form
◊Giant Planets
What Are They, and Where Are They?
Atmospheres
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What's the Deal With Moons?
The Galilean Moons of Jupiter
Moons of Saturn, Uranus, & Neptune
◊Rings
◊Kuiper Belt
Objects
Dwarf Planets
Comets
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Asteroids
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◊Extrasolar
Planets
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Pioneer 10 & 11
Voyager 1 & 2
Galileo
Cassini
New Frontiers
◊Lessons and Activities
Dwarf Planets
Major discoveries in the past decade have forced astronomers to review the definition of a planet. Our solar system now has three classified dwarf planets: our beloved Pluto, Eris, and Ceres.
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Sections:
What Defines a Planet?
Pluto
Pluto's Moons
Eris
Ceres
Related Links
Comets
Comets are icy
planetesimals
that formed in the outer regions of the solar system and assembled in two distinct regions: the
Kuiper belt
and the
Oort cloud
. Comets are rather small compared to planets and moons. The comets that visit the inner solar system are no bigger than 20 km in size — the size of a city!
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Sections:
The Flashy Lives of Comets
Sublimation and the Coma
Comet Tails
The Origin of Comets
Missions to Comets
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