Small Bodies In Space:Small Bodies In Space: Asteroids, Comets Asteroids, Comets

and Meteorsand Meteors

Small Bodies in Space?Small Bodies in Space?

o Besides the sun, 8 planets and their Besides the sun, 8 planets and their moons there are also:moons there are also:o AsteroidsAsteroidso Comets Comets o Meteors Meteors

……or space leftovers?!or space leftovers?!

AsteroidsAsteroids

Asteroid: A rocky object in space that Asteroid: A rocky object in space that can be a few feet wide to several can be a few feet wide to several hundred miles wide.hundred miles wide.

Asteroids are fragile, inactive objectsAsteroids are fragile, inactive objects Majority orbit the sunMajority orbit the sun Are found in the asteroid belt Are found in the asteroid belt

between the orbits of Mars and between the orbits of Mars and JupiterJupiter

Asteroids: Size Asteroids: Size

Range in size: from 1 km across to Range in size: from 1 km across to over 100 km acrossover 100 km across

The first and largest asteroid Ceres; The first and largest asteroid Ceres; was discovered in 1801was discovered in 1801 933 km in diameter933 km in diameter

The smallest asteroid 1991 BA was The smallest asteroid 1991 BA was discovered in 1991discovered in 1991 6 meters across6 meters across

Asteroids: CompositionAsteroids: Composition

Astronomers classify asteroids based Astronomers classify asteroids based on what they are made of: on what they are made of: CarbonCarbon MineralsMinerals

Asteroids: MeasurementAsteroids: Measurement

In 1991 the USA created and In 1991 the USA created and launched the first space probe for launched the first space probe for close range observation of asteroidsclose range observation of asteroids Named GalileoNamed Galileo

First asteroid photographed; GaspraFirst asteroid photographed; Gaspra

Asteroids: MeasurementAsteroids: Measurement

In 1996 National Aeronautics and Space In 1996 National Aeronautics and Space Administration (NASA) launched the Administration (NASA) launched the probe NEAR (Near Earth Asteroid probe NEAR (Near Earth Asteroid Rendezvous)Rendezvous)

Flew by Mathilde in 1997Flew by Mathilde in 1997 Flew by Eros in 1998Flew by Eros in 1998 Landed on Eros in 2001Landed on Eros in 2001 In 2000 it was renamed NEAR-Shoemaker In 2000 it was renamed NEAR-Shoemaker

after an American Astronomerafter an American Astronomer

Asteroids: OrbitAsteroids: Orbit

Orbit: the path a moon, planet, or Orbit: the path a moon, planet, or small body in space takes as it small body in space takes as it travels around another body in spacetravels around another body in space

Most follow an oval-shaped orbit in Most follow an oval-shaped orbit in the asteroid beltthe asteroid belt

Asteroids: OrbitAsteroids: Orbit

Some follow orbits outside the Some follow orbits outside the asteroid belt and follow the same asteroid belt and follow the same orbit as Jupiter; known as Trojansorbit as Jupiter; known as Trojans

Some asteroids are known as near-Some asteroids are known as near-Earth asteroids, they orbit in the Earth asteroids, they orbit in the inner solar systeminner solar system Can cross the orbital path of Mars and Can cross the orbital path of Mars and

EarthEarth

Asteroids: Collisions with Asteroids: Collisions with EarthEarth

Many scientists believe that a near-Many scientists believe that a near-Earth Asteroid collided with Earth Earth Asteroid collided with Earth around 65 million years ago, which around 65 million years ago, which triggered global environmental triggered global environmental changes that led to the extinction of changes that led to the extinction of the dinosaurs.the dinosaurs.

Asteroids: Gravitational Asteroids: Gravitational ForceForce

The gravitational pull from Jupiter and The gravitational pull from Jupiter and other large planets causes asteroid orbits other large planets causes asteroid orbits to slowly changeto slowly change

Orbital changes can lead asteroids to Orbital changes can lead asteroids to collide with one another; increasing the collide with one another; increasing the likelihood of further collisionslikelihood of further collisions

Collisions create smaller asteroids and Collisions create smaller asteroids and fragments. fragments.

Some small fragments reach the earths Some small fragments reach the earths surface as meteorites. surface as meteorites.

Group DiscussionGroup Discussion

Why are there asteroids between Why are there asteroids between Mars and Jupiter instead of a planet? Mars and Jupiter instead of a planet?

Why do you think the asteroid belt is Why do you think the asteroid belt is located where it is? located where it is?

Do you think that there is a high or Do you think that there is a high or low probability that the Earth will be low probability that the Earth will be hit by another large asteroid? Why?hit by another large asteroid? Why?

Comets: Dirty Snowballs Comets: Dirty Snowballs from Spacefrom Space

Comet: A small object made up of ice, Comet: A small object made up of ice, dust and gas that orbit the sun. Jets of dust and gas that orbit the sun. Jets of gas and dust form long tails that reflect gas and dust form long tails that reflect sunlight and can be seen from Earthsunlight and can be seen from Earth

Consist of a solid nucleus core that is Consist of a solid nucleus core that is surrounded by a cloudy atmosphere surrounded by a cloudy atmosphere called a coma and has one or two tailscalled a coma and has one or two tails

Comets are usually only seen through a Comets are usually only seen through a telescopetelescope

Comets: Comets:

Astronomers believe that comets are Astronomers believe that comets are the left over debris from 4.6 billion the left over debris from 4.6 billion years ago when the outer planets years ago when the outer planets were first formedwere first formed

Comets: ClassificationComets: Classification

Astronomers classify comets Astronomers classify comets according to how long they take to according to how long they take to orbit the sunorbit the sun Short-Period comets need less than 200 Short-Period comets need less than 200

years to complete one orbityears to complete one orbit Long-Period comets takes 200 years or Long-Period comets takes 200 years or

more to complete one orbit more to complete one orbit

Comets: The Kuiper BeltComets: The Kuiper Belt

Scientists think that short-period comets Scientists think that short-period comets come from a band of objects called the come from a band of objects called the Kuiper belt; which lies beyond the orbit Kuiper belt; which lies beyond the orbit of Plutoof Pluto

Within the Kuiper belt comets are Within the Kuiper belt comets are inactiveinactive

The gravitational pull of the outer planets The gravitational pull of the outer planets can shift objects out of the Kuiper belt can shift objects out of the Kuiper belt and into the inner solar system where and into the inner solar system where they become active cometsthey become active comets

Comets: The Oort CloudComets: The Oort Cloud

Long-period comets come from the Oort Long-period comets come from the Oort cloud; a nearly spherical collection of icy cloud; a nearly spherical collection of icy bodies about 1,000 times farther away bodies about 1,000 times farther away from the sun than Plutofrom the sun than Pluto

Within the Oort cloud comets are Within the Oort cloud comets are inactiveinactive

Gravitational interactions with passing Gravitational interactions with passing stars can cause the icy bodies in the Oort stars can cause the icy bodies in the Oort cloud to enter the inner solar system and cloud to enter the inner solar system and become active cometsbecome active comets

CometsComets

Comets move in long, oval shaped Comets move in long, oval shaped orbits that can cross the almost orbits that can cross the almost circular orbit of the planets.circular orbit of the planets.

Sometimes comets collide with Sometimes comets collide with planets and their moons; the planets and their moons; the majority of impact craters across the majority of impact craters across the galaxy are a result of comet galaxy are a result of comet collisionscollisions

Comets: Life Comets: Life

Comets lose ice and dust each time they Comets lose ice and dust each time they return to the inner solar system; leaving return to the inner solar system; leaving behind trails of dusty debrisbehind trails of dusty debris

When Earth travel through on of these When Earth travel through on of these trails the debris become meteors that trails the debris become meteors that burn up into the Earths atmosphere.burn up into the Earths atmosphere.

Eventually a comet will lose all of its ice, Eventually a comet will lose all of its ice, it will then break up and dissipate into it will then break up and dissipate into clouds of dust or turn into fragile, inactive clouds of dust or turn into fragile, inactive objects (similar to asteroids)objects (similar to asteroids)

Comets: Halley’s CometComets: Halley’s Comet

Originally discovered in 1682 by Sir Originally discovered in 1682 by Sir Edmund HalleyEdmund Halley

Passes earth every 76 yearsPasses earth every 76 years Most famous comet Most famous comet When it passed near Earth in 1986, When it passed near Earth in 1986,

five spacecraft flew past the comet five spacecraft flew past the comet and gathered information about its and gathered information about its appearance and chemical compositionappearance and chemical composition

Group DiscussionGroup Discussion

If Halley was discovered in 1782, and If Halley was discovered in 1782, and Halley takes 76 years to orbit the sun, Halley takes 76 years to orbit the sun, roughly when will Halley pass earth roughly when will Halley pass earth again? How old will you be?again? How old will you be?

Do you think there will be visible Do you think there will be visible differences in Halley’s comet the next differences in Halley’s comet the next time it appears? What differences time it appears? What differences would you expect to see? would you expect to see?

How many more times do you predict How many more times do you predict Halley will pass by earth again? Why? Halley will pass by earth again? Why?

ANSWERANSWER

The next time the Halley comet will The next time the Halley comet will pass earth will be in 2062pass earth will be in 2062

Meteors:Meteors:

Meteor: Appear when a chunk of metallic Meteor: Appear when a chunk of metallic or stony matter called a meteoroid enters or stony matter called a meteoroid enters the Earths atmosphere from outer space the Earths atmosphere from outer space

A bright streak of light that appears A bright streak of light that appears briefly in the sky: can be seen with the briefly in the sky: can be seen with the unaided eyeunaided eye Often called falling/shooting starsOften called falling/shooting stars

Meteoroids come from broken, Meteoroids come from broken, disintegrated pieces of comets and disintegrated pieces of comets and asteroids asteroids

MeteorsMeteors

Air friction heats up the meteoroid Air friction heats up the meteoroid chunk and causes it to glow and chunk and causes it to glow and create a shining trail of gases and create a shining trail of gases and melted particlesmelted particles

Most glow for about a second, Most glow for about a second, Most disintegrate long before Most disintegrate long before

touching the Earths surfacetouching the Earths surface Meteoroids that reach the Earths Meteoroids that reach the Earths

surface are called meteorites surface are called meteorites

MeteorsMeteors

Millions of meteors occur in the Millions of meteors occur in the Earths atmosphere every day – most Earths atmosphere every day – most are no bigger than a pebbleare no bigger than a pebble

Meteoroids travel around the sun in Meteoroids travel around the sun in a variety of orbit shapes and a variety of orbit shapes and velocitiesvelocities Fastest ones move 42 km per secondFastest ones move 42 km per second

MeteorsMeteors

The earth encounters a number of streams The earth encounters a number of streams (trails) or swarms (clusters) of tiny (trails) or swarms (clusters) of tiny meteoroids at certain times of the year.meteoroids at certain times of the year. Streams and swarms have oval-shaped orbits like Streams and swarms have oval-shaped orbits like

cometscomets The most brilliant meteor shower took place The most brilliant meteor shower took place

in November 12-13 1833. Since then this in November 12-13 1833. Since then this meteor shower continues to take place every meteor shower continues to take place every November and seems to come from the November and seems to come from the direction of the constellation Leo (Leonid direction of the constellation Leo (Leonid Shower) Shower)

Meteors: TypesMeteors: Types

There are three kinds of meteors:There are three kinds of meteors: Stony: consist of minerals rich in silicon Stony: consist of minerals rich in silicon

and oxygen and come from the outer and oxygen and come from the outer crust of a comet/asteroid crust of a comet/asteroid

Iron: consist mostly of iron and nickel Iron: consist mostly of iron and nickel and comes from the metallic core of a and comes from the metallic core of a comet/asteroidcomet/asteroid

Stony-iron: Consists of equal amounts of Stony-iron: Consists of equal amounts of silicon/oxygen and iron/nickel and come silicon/oxygen and iron/nickel and come from the inner crust of a comet/asteroid from the inner crust of a comet/asteroid

Meteors: SizeMeteors: Size Meteor size varies; most are relatively small Meteor size varies; most are relatively small Larger bodies like asteroids and comets can Larger bodies like asteroids and comets can

also strike the earth and become meteorites.also strike the earth and become meteorites. Meteors will only strike the earth surface Meteors will only strike the earth surface

when they are just the right size, if they are when they are just the right size, if they are too small they disintegrate into the too small they disintegrate into the atmosphere, if they are too big they will atmosphere, if they are too big they will often explode when they hit the atmosphere often explode when they hit the atmosphere – raining down much smaller pieces– raining down much smaller pieces

Thousands of small meteorites have been Thousands of small meteorites have been found in Antarctica, which have provided found in Antarctica, which have provided scientists with clues to the types of materials scientists with clues to the types of materials that form planets that form planets

Meteors: Impact Craters Meteors: Impact Craters

Scientists have found more than 120 impact Scientists have found more than 120 impact craters/basins on earth from meteors, craters/basins on earth from meteors, comets, asteroids.comets, asteroids.

Most famous: Meteor Crater in Arizona Most famous: Meteor Crater in Arizona 1, 275 meters across and 175 meters deep1, 275 meters across and 175 meters deep Formed nearly 50, 000 years ago when an iron Formed nearly 50, 000 years ago when an iron

meteorite weighing 330, 000 metric tons struck meteorite weighing 330, 000 metric tons struck the Earth the Earth

Most impact points larger than the meteor Most impact points larger than the meteor crater have been worn away by time and crater have been worn away by time and surface changessurface changes

Group DiscussionGroup Discussion

Why do people confuse a falling Why do people confuse a falling meteor with a falling star?meteor with a falling star?

When you think about or see a When you think about or see a falling meteor how does it make you falling meteor how does it make you feel? feel?

Do you really think it is possible to Do you really think it is possible to know what small body a meteor know what small body a meteor came from?came from?