Chapter 28.4 Asteroids, Comets & Meteoroids

Std 1f: Know the evidence for the dramatic effects that asteroid impacts have had in shaping the surface of planets and their moons and in mass extinctions of life on Earth Objective 1: Describe the physical characteristics of asteroids and comets Objective 2: Describe the Kuiper Belt and the Oort CloudObjective 3: Compare meteoroids, meteorites and meteors

Asteroids

• Asteroids - a small, rocky object that orbits the sun– The largest of the

small bodies in the solar system

–More than 50,000 have been discovered

– The larger asteroids are known as “minor planets”

Asteroid Belt

• Most asteroids are located in a region between Mars and Jupiter known as the Asteroid Belt

Composition of Asteroids

• Composition (made out of) is similar to inner planets – 3 categories of

asteroids composition:• 1) Silicate

materials • 2) Iron & Nickel • 3) Carbon material

(rarest)

Near-Earth Asteroids

• More than 1,000 asteroids have orbits that bring them very close to Earth

• Asteroids could strike Earth causing significant damage • Asteroid detection programs track these near-Earth

asteroids to help predict possible collisions

Comets

• Comets - small bodies of ice, rock and cosmic dust with an elliptical orbit around the sun

• It gives off gas and dust in the form of a tail as it passes close to the sun

• Most famous is Halley’s Comet which passes by Earth every 76 years (last time 1986)

• Hale-Bopp passed by in 1997

Composition of comets

• Comets have several parts:–Core (nucleus)- made of rock, metals, and

ice –Coma- a spherical cloud of gas and dust

surrounds the core (core & coma form the head of the comet)–Tail- form when sunlight changes the

comet’s ices to gases. Solar wind pushes the gas away from the sun

Objective 1: Describe the physical characteristics of asteroids and comets

• Where are most asteroids found?– Between Mars and Jupiter (Asteroid belt)

• What are the 3 different compositions of asteroids?– Silicate materials, nickel and iron, and Carbon

• What is a small, icy, rocky object that orbits the sun?– comet

• What are the 3 parts that make up a comet?– Core, coma, tail

Comets

The Oort cloud

• Most comets originate in the Oort cloud • Oort cloud - a spherical cloud of dust and ice that

surrounds the solar system and extends from the Kuiper belt to almost halfway to the nearest star

• Long-period comets – comets that take more than 200 years to complete one orbit of the sun

The Kuiper belt

• Pluto may be the largest body in this belt • Kuiper belt - A region of the solar system just

beyond the orbit of Neptune that contains small bodies of mainly ice

Objective 2: Describe the Kuiper Belt and the Oort Cloud

• Where is the Kuiper belt located?– Beyond Neptune

• Where is the Oort cloud located?– Surround the solar system almost to the next star

• Where do most comet originate?– Oort cloud

• What is the largest body in the Kuiper belt?– Pluto

Short period comets

• They take less than 200 years to complete one orbit around the sun

• Halley’s comet is a short period comet

Meteoroids (in space)

• Meteoroids -A relatively small, rocky body that travels through space– Diameter is less than 1mm– They are probably pieces of matter that come from

passing comets – Produce meteor showers• Lyrid meteor shower (caused by dust from

Thatcher comet)• Peaks April 22 (best viewing 3:30 – 4:40am)

Meteors (in the atmosphere)

• Meteors -A bright streak of light that results when a meteoroid burns up in Earth’s atmosphere

• Meteors are commonly called shooting stars• Meteoroids sometimes vaporize very quickly in a

brilliant flash of light called a fire ball• Meteor shower - A large number of small meteoroids

entering Earth’s atmosphere in a short period of time• D New report • Amazing video

Meteorites (hits Earth)

• Large meteors may not burn up completely in the atmosphere

• If it hits the Earth’s surface it is known as a meteorite

3 types of meteors:

1) Stony

2) Iron

3) Stony iron

Objective 3: Compare meteoroids, meteorites and meteors

• What is a small rocky body that travels through space?– meteoroid

• What is the bright streak of light caused by meteoroid burning up? – meteor

• What is a meteor that hits the Earth?– meteorite

• What are 3 types of meteors?– Stoney, iron, stoney iron