Comets, Asteroids, and Comets, Asteroids, and MeteorsMeteors

Chapter 14.5Page 572

Comets

• Often, we refer to comets as dirty snowballs…this is because– Comets are chunks of ice and dust whose

orbits are usually very long, narrow ellipses.

tail

coma

nucleus

The inner core of the comet is called the nucleus. The comet’s head is called the coma.The tail of the comet is composed of gas and dust being pushed away from the coma.

CometsBecause their orbits are so elliptical, few pass near

Earth and when they do they are only seen briefly.• Since comets have an orbit, we usually will see the

same comet every several years. Ex: Haley’s comets passes by Earth every 76 years. Last seen: 1986, next seen 2062.

– When a comet gets to close to the sun, the energy from the sunlight turns the ice into gas, releasing the dust.

– The dust and gas form the outer layer called the coma.

Origin of Comets• Most comets originate from one of two

distant regions: the Kuiper belt or the Oort cloud

Kuiper Belt Oort Cloud

Asteroids• Asteroids are objects that are too small

and numerous to be called planets. • Most asteroids revolve around the sun

between the orbits of Mars and Jupiter.– This region is known as the asteroid belt.

• Some asteroids come near the orbit of Earth. (Five actually revolve Earth)

• Asteroids that impact on Earth can cause great devastation depending on its size.

http://images.google.com/imgres?imgurl=http://www.pbs.org/wgbh/nova/gamma/images/cosm_asteroid_large.jpg&imgrefurl=http://www.pbs.org/wgbh/nova/gamma/cosm_aste.html&h=500&w=457&sz=37&hl=en&start=53&tbnid=buQJxsYK-y5bBM:&tbnh=130&tbnw=119&prev=/images%3Fq%3DAsteroid%26start%3D40%26gbv%3D2%26ndsp%3D20%26hl%3Den%26sa%3DN

Origin of Asteroids

• Theory 1: Asteroids are the remains of a shattered planet.

• Theory 2: Asteroids are left over pieces of the early solar system that never came together.

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

– Meteoroids usually come from remains of comets or asteroids.

– When a comet breaks up, the cloud of dust continues to move through the solar system.

– When Earth passes through this cloud of dust, bits of dust enter Earth’s atmosphere.

• When a meteoroid passes through Earth’s atmosphere, friction makes it burn up and produce a streak of light…this is a meteor.

• Meteoroids that pass through Earth’s atmosphere and hit Earth’s surface are called meteorites.

Other “shooting stars” …

Homework

• Read Section 5 of Chapter 14• Answer the Assessment Questions on

page 575.