Ch 9 Jane Lucas

Jane Lucas
Astronomy 100-Week 10 – Chapter 9
Asteroids
Meteorites
Asteroid Belt
Comets
Oort Cloud
Kuiper Belt
Pluto
Dwarf Planets
Cosmic Collisions
Asteroids are rocky leftover planetsimals which are chunks of rock that still orbit the Sun because they never managed to become a part of a planet.  They come in a wide variety of sizes.  The largest asteroid is the Ceres.  Ceres is considered a dwarf planet because of its large size.  There are many other asteroids that are large enough to be dwarf planets.  There are many smaller asteroids than larger ones.  Smaller asteroids are not spherical, because they are too small for their gravity to have reshaped their rocky material.
Meteorites are pieces of rock that have fallen to the ground from space.  The types of meteorites are primitive and processed.  Primitive meteorites are sample mixtures of rock and metal, sometimes also containing carbon compounds and small amounts of water.  Processed meteorites appear to be pieces of large asteroids that underwent differentiation into a core-mantle-crust structure.  Some of these are made mostly of iron while others are rocky.  
Asteroid belt is the region of our solar system between the orbits of Mars and Jupiter in which asteroids are heavily concentrated.  This was the only place that rocky planetesimals could survive for billions of years.  
Comets are ice-rich objects and are known as small solar system bodies.  They are ice rich because they are formed beyond the frost line.  Sometimes comets have tails and they grow them only as they enter the solar system.  The tails are heated by the warmth of the Sun.  Far from the Sun the comet is completely frozen.  Comets have two visible tails which are the plasma tail and the dust tail.  
Oort cloud is a huge spherical region centered on the Sun, extending perhaps halfway to the nearest starts, in which trillions of comets orbit the Sun with random inclinations, orbital directions, and eccentricities.  
Kuiper belt is the comet-rich region of our solar system that spans distances of about 30-100 AU from the Sun.  The Kuiper belt comets have orbits that lie fairly close to the plane of planetary orbits and travel around the Sun in the same direction as the planets.  
Pluto is proved to be misfit among the planets in size and composition.  It is far smaller than even the terrestrial planets, and its ice-rich composition fits neither the terrestrial or jovian categories.  So Pluto’s composition and orbit indicate that it is a large comet of the Kuiper belt.  
Dwarf planets are Pluto, Eris, Makemake, and Haumea.  They all qualify as dwarf planets because they are big enough to be round but have not cleared their orbital neighborhoods.  Dozens of other objects of the Kuiper belt may also qualify as dwarf planets.  
Cosmic collisions not only bring meteorites and leave impact craters, but can affect life here on Earth.  Impacts are always linked in at least some way to gravitational influences of Jupiter and the other jovian planets.  These influences have shaped the asteroid belt, the Kuiper belt, and the Oort cloud and continue to determine when an object is flung our way.  
Chapter 9 studies the solar system by studying the smallest objects other than the terrestrial and jovian planets.  We studied the asteroids, comets, and meteorites and how they helped form the solar system.  The jovian planets shaped the asteroid belt, the Kuiper belt, and the Oort cloud.  We learned about Pluto and other dwarf planets.  In chapter ended with the impact of collisions that pose a threat in the future and could of destroyed the past.