Final. Planetary Rings, Asteroids & Comets, Meteors & Meteorites. Flashcards
Jupiter’s Rings
Rocky, very fine rocky dust. Broad, diffuse rings.
Roche Limit
the distance from a planet within which a moon cannot hold itself together by its own gravity. If a moon went in, it would be ripped apart by tidal forces.
Rings lie in this area b/c the material cannot condense together to form an object, so it is just debris scattered around the planet forming a ring.
(If moons were in roche limit, they would be egg shaped b/c tidal stretching.)
Saturn’s Rings
Made up of billions of ice particles (large chunks). Not as old as the planet itself. Golf ball to boulder sized. Further: dust size.
What caused Saturn’s rings
(maybe) Instead of nebula forming them when the planet formed, may have formed from the debris from impact collisions on Saturn’s moons. Same for Neptune and Uranus. Rings we see today may be temp b/c they were caused by impacts and eventually the ice will dissipate.
Shepard Satellite
a satellite or chunk of debris that confines particles to planetary rings b/c gravity.
Asteroids
Sometimes called minor planets, small rocky worlds, most orbit sun b/w Mars and Jupiter.
Kuiper Belt
located in the outer fringes of our solar system, more than a million dark, icy bodies, some of which are very large. This is larger than the asteroid belt.
comet
A chunk of debris that is composed of frozen icy material and frozen grains of rock. They can be very bright as they orbit the sun. Have a tail that is rather bright.
Meteors
“shooting stars” parts of an asteroid (usually) that pass through our atmosphere and burn up, creating a small flash across the sky.
Meteoroid
The object that is going to enter the atmosphere before it actually enters. So when you see the meteor, before it entered the atmosphere, it was a meteoroid while it was still outside the planet.
Meteorite
Any part of an object that actually makes it to earth’s surface.
Why do comets develop tails?
since they are frozen and are orbiting the sun, the heat from the sun will cause the comet’s body to melt a bit as it gets closer and closer. The icy material will vaporize and it releases gas as dust, giving it a tail. Can be longer than an AU.
Solid frozen part of a comet
nucleus. only a few km in diameter.
Meteor and Meteoroid
not the same thing.
Asteroid - shape
irregular shape and have a lot of impact craters on surface. look like chunks of rubble.
Combined mass of asteroid belt
not enough to make up the size of the earth. only 1/20th the size of earths moon.
Some of the largest asteroids
could be broken into planetesimals.
Oort cloud
spherical, can extend from 10,000 to 100,000 AU from the sun.
Astronomers think the objects in Oort cloud formed in the region among the Jovian planets. As the planets grew larger, they prob ejected much of the icy debris out toward the Oort cloud where they developed into comets.
Objects in Kuiper belt
evidently formed as icy planetesimals in the outer solar nebula not much further from the sun than the outer planets.
How big are the particles that produce typical meteors?
less than 1 gram in mass. Therefore, we don’t have nearly as many meteorites as we do meteors because most can’t survive the burning long enough to make it to the surface of the planet.
Meteor Showers
displays of meteors that all seem to come from one origin in the sky, so they are related. Happen when the Earth passes near the orbit of a comet. As we do this, the particles of dust and debris that are flying off of the nucleus of the comet are left floating in space as they enter our atmosphere in a parallel pattern as we move in our orbit.
Most meteors we see come from
tiny bits of debris from comets.
Meteorites come from
asteroids. The chunks broken off the asteroids are the only particles that can be large enough to survive vaporizing within the Earth’s atmosphere.
