1 Comets, Asteroids, and Meteors By: Annette Miles
2 What is a comet? A comet is a small body which scientists sometimes call a planetesimal. They are made out of dust, ice rock, gas, and. They are kind of like a dirty. snowball
3 Comets are made up of different parts. The nucleus The coma The ion tail The dust tail The hydrogen envelope
4 The nucleus is the frozen center of a comet s head. It is composed of, ice, gas and dust. The nucleus contains most of the comet s mass and measure about 10 miles across or less.
5 The nucleus of Halley s Comet
6 The coma is a spherical blob of gas that surrounds the nucleus of a comet. As the comet gets closer to the sun, the heat vaporizes some of the ice and causes the comet to spew gas and dust particles into space. The and nucleus the coma form the head of a comet.
7 The ion tail is made of electrically charged gas molecules that are being pushed away from the nucleus by the solar wind. (The blue tail in the picture.)
8 When a comet is approaching the Sun, the ion tail trails the comet: when the comet is leaving of the Sun, the ion tail leads. The tail fades as the comet moves far from the Sun. The ion tail can be well over 100 million km long.
9 The dust tail develops when the comet is near the Sun. This tail is made of small dust particles that have evaporated from the nucleus and are being pushed away from the comet. The tail slightly due to the comet s motion.
10 The tail can be up to 250 million km long, and is most of what we see. Comets are only visible when they're near the sun in their elliptical orbits. Comet Hale Bopp showing its two tails. Courtesy of NASA
12 Hale-Bopp The Great Comet of 1997
13 Surrounding the coma is an invisible layer of hydrogen that has been released. It is the hydrogen envelope. This cannot be seen from Earth because its light is absorbed by our atmosphere. It is usually between the ion tail and the dust tail.
14 Can you identify the following parts of a comet? 1. Ion tail 4. Hydrogen envelope 2. Nucleus 3. Coma 5. Dust cloud
15 Comets orbit the Sun in highly elliptical orbits. Their speed increases greatly when they are near the Sun and slows down at the far reaches of the orbit. Since the comet is light only when it is near the Sun, comets are dark throughout most of their orbit.
16 Comets originate from either the Kuiper Belt (beyond the orbit of Neptune) or the Oort Cloud (which surrounds the outer reaches of the solar system.)
17 Videos on Comets Animation of a Comet
18 ASTEROIDS Asteroids are rocky or metallic objects, also know as planetoids or minor planets that revolve around our Sun.
19 Most asteroids orbit the Sun in the asteroid belt located between Mars and. Jupiter A few asteroids approach the Sun more closely. The asteroids in the asteroid belt have a slightly elliptical orbit. The time for one revolution around the Sun varies from about 3 to 6 Earth years
20 Asteroids range in size from tiny pebbles to about 578 miles (930 kilometers) in diameter. Sixteen of the 3,000 known asteroids are over 150 miles (240 km) in diameter.
21 Asteroid Ceres Diameter of 590miles (950 km) Largest asteroid and only dwarf planet in the inner Solar System Asteroid Vesta Diameter of 326 miles (525 km) Brightest asteroid visible from the Earth.
22 Some asteroids even have orbiting moons. Here is the asteroid 243 Ida and its tiny asteroid moon, Dactyl. This is the first asteroid ever found with an orbiting moon. Ida's dimensions are about 35 x 15 x 13 miles. Dactyl is only about 1 mile across.
23 METEOROIDS, METEORS, and METEORITES Meteoroids are small bodies that travel through space. Most meteoroids are smaller than the size of a. pebble Meteoroids are tiny particles left by an asteroid or a comet.
24 A meteor is a meteoroid that has entered the, Earth s atmosphere usually making a fiery trail as it falls. It is sometimes called a shooting star or a falling star.
25 A meteor shower is a phenomenon in which many meteors fall through the atmosphere in a relatively short time and in approximately parallel trajectories. Arizona, November The Leonid meteor shower rained 2,300 meteors per minute for 20 minutes. (Photo NASA)
26 Video of meteor Shower or_shower_geminid/
27 A meteorite is a meteor that has fallen and struck the Earth. These rare objects have survived a fiery fall through the Earth's atmosphere and have lost a lot of mass during that process.
28 Near Winslow, Arizona, you can visit a crater that was made from a meteorite. The crater is nearly one mile across, 2.4 miles in circumference, and more than 500 feet deep. Animation on the formation of this crater.