Solar System Stuff

Key Terms: Asteroid - Dark, rocky remains of larger bodies that formed under the control of Jupiter’s gravity. They are essentially, small planets. Asteroid Belt – Occupies the space in between the orbits of Mars and Jupiter and contains over a billion asteroids ranging from pebble–sized to kilometers in diameter. Comet –A mass of ice (or “dirty snow”) that has a very elongated and eccentric orbit around the sun. As they come closer to the sun, the material boils away, creating two tails – one of gas, one of dust. Meteor- Debris shed by comets and asteroids (space grit) that makes its way into the Earth’s atmosphere Meteorite – A meteor that impacts the Earth’s surface before it is vaporized by the Earth’s atmosphere a celestial body orbiting a star that is massive enough to be rounded by its own gravity but has not cleared its neighboring region of planetesimals and is not a satellite. More explicitly, it has to have sufficient mass to overcome its  Dwarf Planet - orbits a star and massive enough to be round by its own gravity but has not cleared its neighboring region of other objects

The Asteroid Belt There is a catalog of over 35,000 named asteroids in this 3 AU thick region between Mars and Jupiter. Notice that a large number are also in Jupiter’s orbit. A combination of computer modeling and Hubble data make Vesta one of the most studied asteroids. The largest known, Ceres has an approximate diameter of 1,000km Because of collisions within the asteroid belt, fragments often fall towards the inner planets. There are over 200 known asteroids that cross the Earth’s orbit.

Comets Do Comets Ever Hit Things? A mysterious and very cold region lying 50,000 AU’s from the Sun called the Oort Cloud is an area in which scientists believe most comets originate from. This material likely migrated to it’s present location after being formed with Neptune and Uranus – no one really knows exactly! Because most comets have very large elliptical orbits around the Sun, we only see them when they are in the close range of solar radiation that vaporizes material from their nucleus (creating a coma ) causing a “tail” Halley’s Comet only approaches close enough to the sun to be seen from Earth every 76 years Do Comets Ever Hit Things? In 1994, Comet SL9 (est. 5km diam.) was observed impacting Jupiter in 20 pieces. The energy delivered equaled around 6 million megatons - 600 times the world’s current nuclear arsenal!

M e t e o r s A meteor is a bright streak of light in the sky (a "shooting star" or a "falling star") produced by the entry of a small meteoroid into the Earth's atmosphere. If you have a dark clear sky you will probably see a few per hour on an average night; during one of the annual Meteor Showers you may see as many as 100/hour. Meteorites are bits of the solar system that have fallen to the Earth. Most come from asteroids, a few probably come from comets. A small number of meteorites have been shown to be of Lunar (23 finds) or Martian (22) origin. Though meteorites may appear to be just boring rocks, they are extremely important in that we can analyze them carefully in our labs. Aside from the few kilos of moon rocks brought back by the Apollo and Luna missions, meteorites are our only material evidence of the universe beyond the Earth. The average meteoroid enters the atmosphere at between 10 and 70 km/sec. But all but the very largest are quickly decelerated to a few hundred km/hour by atmospheric friction and (if they don’t vaporize) hit the Earth's surface with very little fanfare. However, meteoroids larger than a few hundred tons are slowed very little; only these large (and fortunately rare) ones make craters on the earth’s surface A good example of what happens when a small asteroid hits the Earth is Barringer Crater (a.k.a. Meteor Crater) near Winslow, Arizona. It was formed about 50,000 years ago by an iron meteor about 30-50 meters in diameter. The crater is 1,200 meters in diameter and 200 meters deep. About 120 impact craters have been identified on the Earth, so far. .

The Kuiper Belt The Kuiper Belt is a region of the Solar System beyond the planets, extending from the orbit of Neptune. It is similar to the asteroid belt, although it is far larger -- 20 times as wide and 20–200 times as massive. Like the asteroid belt, it consists mainly of small bodies (remnants from the Solar System's formation that did not become part of a planet). It is home to at least three Dwarf Planets – including Pluto and Eris (27% larger than Pluto). But while the asteroid belt is composed primarily of rock and metal, the Kuiper Belt objects are composed largely of frozen ice. P l u t o Clearest picture so far – HST 1994 Status: Dwarf Planet Diameter: 2,274 Km Orbit: About 6 billion Km from Sun, 248 Earth years Discovery: 1930 (Clyde Tombaugh) Avg. Temp.: -255°C to -210°C Surface: 98% Nitrogen with a very thin atmosphere. Largest Moon: Charon (1,172 Km diameter)

Lab Ticket Lab Ticket Name: ________________ Name: ________________ What are the 2 main differences between Comets and Asteroids? ____________________________________________________________________ What exactly is a shooting star ? Where exactly is the asteroid belt and how do asteroids “leave” the area? Why might a particular comet only appear every many 1000’s of years and what makes these objects visible? Why does our moon look very “cratered”, while the earth does not? Why is Pluto no longer classified as a planet ? Name: ________________ Lab Ticket What are the 2 main differences between Comets and Asteroids? ____________________________________________________________________ What exactly is a shooting star ? Where exactly is the asteroid belt and how do asteroids “leave” the area? Why might a particular comet only appear every many 1000’s of years and what makes these objects visible? Why does our moon look very “cratered”, while the earth does not? Why is Pluto no longer classified as a planet ?