Chapter 9 Notes Jessica Brandon

Chapter 9 asteroids comets and dwarf planets

***9.1 asteroids and meteoroids***

·      Asteroids leave trails in long-exposure images because of their orbital motion around the sun.

·      Asteroid facts asteroids are rocky leftover of planet formation. Small asteroids are more common than large asteroids. All the asteroids in the solar system wouldn't add up even a small terrestrial planet.

·      Asteroids are cratered and not round.

·      Some large asteroids have their own moons

·      Asteroids Ida has a tiny moon named Dactyl

·      Most asteroids orbit in a belt between mars and Jupiter

·      Trojan asteroids follow Jupiter orbit

·      Orbits of near Earth asteroids cross earths orbit.

·      Asteroids in orbital resonance with Jupiter experience periodic nudge

·      Eventually those nudge move asteroids out of resonant orbits, leaving gaps in the belt.

·      Rocky planetesimal between mars and Jupiter  did not accurate into a planet

·      Jupiter's gravity through influence of resonance stirred.

·      Origin of meteorites, most meteoroids are pieces of asteroids

·      Meteorite: a rock from space that falls through earths atmosphere

·      Meteor the bright trail left by a meteorite

·      Primitive unchanged in composition since they first formed 4.6 billion years ago

·      Processed younger, have experienced processes such as volcanism or differentiation.

·      Meteorites from the moon and mars: a few meteorites arrive on earth from the moon and mars

·      Composition differ from the asteroid fragments

·      This is a cheap but slow way to acquire moon rocks and mars rocks.

***9.2 Comets***

·      Formed beyond the frost line, comets are icy counterparts to asteroids

·      The nucleus of a comet is like a dirty snowball

·      Most comets do not have tails

·      Most comets remain perpetually frozen in the outer solar system

·      Only comets that enter the inner solar system grow tails

·      A dirty snowball. Source of material for comets tail

·      Coma is atmosphere that comes heated nucleus

·      Plasma tail is gas escaping from coma pushed by solar wind

·      Dust tail is pushed by photons

·      Mission to study nucleus of comet temple 1

·      Projectile hit surface on July 4, 2005

·      Many telescopes studied aftermath of impact

·      Comets eject small particles that follow the comet around in its Ortiz and cause mayor sower when earth crosses the comets orbit

·      Meteors in a shower appears to emanate from the same are of sky because earths motion through space.

·      Only a tiny number of comets enter the inner solar system most stay far from the sun

·      Oort Cloud comets on random orbits extending to about 50,000 AU

·      Kuiper belt comets on orderly orbits at 30-100 AU in disk of solar system

***9.3 Pluto lone dog no more***

·      Pluto orbit is tilted and significantly elliptical

·      Neptune orbits three times during the time Pluto orbits twice resonance prevent a Collision.

·      Is Pluto a planet?

·      Much smaller than the eight major planets. Not a gas giant like the outer planets. Has an icy composition like a comet. Have a very elliptical, inclined orbit.

·      There are many icy objects like Pluto on elliptical inclined orbits beyond Neptune. The largest ones are comparable in size to earths moons.

·      These large icy objects have orbits similar to the ,smaller objects in the kuiper  belt that become short period comets.

·      Its the largest moon Charon is nearly as large as Pluto itself probably made by a major impact. Pluto is very cold. Pluto has a thin nitrogen atmosphere that refreezes  onto the surface as Pluto orbits takes it farther from the sun.

***9.4 cosmic collision small bodies versus the planets***

·      This crater chain on Callisto probably came from another comet that tribal forces tore to pieces.

·      Impact plume from a fragment of comet SL9 rises high above Jupiter's surface.