Mav Mark11/14/11

List all 8 planets in order of distance from the sun.

Comets, Asteroids, and Meteors

Notes

Comets

•A comet orbits the sun. A comet is made of ice, dust, and small rocky particles. You can think of a comet as a “dirty snowball.”

Comet Hale–Bopp

, as seen on 29 March 1997 in Pazin, Croatia

Comets•The brightest part of a comet is the head.

A comet’s head is made up of a nucleus and a coma. The nucleus is the solid core of the comet. The coma is a fuzzy outer layer made up of clouds of gas and dust.

•A comet’s tail usually consists of two parts: an ion tail and a gas tail. Both tails usually point away from the sun; one tail is made of gases, and the other is made of electrically charged particles.

Comets

•The orbit of a comet is highly elliptical, therefore it takes a very long time for comets to orbit the sun.

Comets•Most comets originate in one of two regions

surrounding the solar system:

• The Kuiper Belt is a doughnut-shaped region that extends from beyond Neptune’s orbit to about 100 times Earth’s distance from the sun.

• The Oort Cloud is a spherical region of comets that surrounds the solar system out to more than 1,000 times the distance between Pluto and the sun.

Asteroids

•An asteroid is a rocky object that orbits the sun, but is still too small to be considered a planet.

•Most asteroids are in orbit between Mars and Jupiter. The region of the solar system is called the asteroid belt.

Asteroids• Most asteroids are less than one kilometer in

diameter, but some are much larger, bringing the number of asteroids up to over 1,000,000.

• Astronomers believe that asteroids are leftover pieces of rock from the early solar system.

• The total mass of the asteroid belt is estimated to be just ¼ of the mass of the Luna. The four largest objects, Ceres, Vesta, Pallas, and Hygiea, account for half of the belt's total mass, with almost one-third accounted for by Ceres alone.

• Ceres is now one of our five dwarf planets.

Ceres, Luna, and Earth

Number 1 is Ceres, 4 is Vesta, 2 is Pallas, and 10 is Hygeia in the asteroid belt, compared to

our moon in the background.

Asteroids•Occasionally, asteroids can leave the asteroid

belt due to collision or gravitational disturbances from Mars or Jupiter.

•These loose asteroids can travel around the sun in much more elliptical orbits, which can put then in the paths of planets.

•These impacts have been known to impact Earth every 50 million years or so. The last major impact was the K-T (Cretaceous-Tertiary) impact that led to the extinction of the dinosaurs 65 million years ago.

Meteors•A meteoroid is a chunk of rock or dust in

space.

•Some meteoroids from when asteroids crash into each other. Other meteoroids from when comets break apart.

•Meteoroids can enter Earth’s atmosphere. When one does, friction between the meteoroid and the air produces a streak of light in the sky. A meteor is a streak of light in the night sky produced by a meteoroid. Think: meteor shower.

Meteors

•Most meteoroids burn up completely in that atmosphere, turning into nothing but the dust you see floating in front of bright lights.

•However, some will strike Earth’s surface. Meteoroids that hit the ground (or a house, car, person, animal, etc.) are called meteorites.

Possible life-forms on a meteorite in AntarcticaMile-wide crater in Arizona

Largest meteorite ever found in America

Discovered meteorites can usually be sold to museums and science labs for tens to

thousands of dollars each.