Chapter 3Solar System

Section 4Asteroids, Comets and

MeteoroidsNotes 3-6

Asteroids

Largest of the small bodies in the solar system

Fragments of rock that orbit the sun

Orbits are ellipses Ceres is found in the asteroid

belt but is now called a dwarf planet. About 1,000 km in diameter

Asteroids Asteroid Belt

Region between Mars and Jupiter Most asteroids can be found there Begins around 100 million km beyond

Mars’ orbit and continues for 150 million km toward Jupiter

Classified according to composition Carbon: gives a dark appearance Iron and nickel: have a metallic look Silicate minerals: most are this; look like

earth rocks

Asteroids

Believed that these are the remains of planetesimals that didn’t not form a planet Mostly because of Jupiter’s strong

gravitational force Trojan Asteroids: are also called

earth-grazers Orbit the sun but are not in the

asteroid belt Found around Jupiter Occasionally they do collide with

Earth

Comets

Comet: Body of rock, dust, methane,

ammonia and ice Nucleus: made of rock, metals and

ice Around 1km to 100 km in diameter

Orbit the sun in long ellipses Cloud of gas and dust is called the

coma Nucleus and coma form the head of the

comet Bright appearance is from light

reflecting off of it

Comets

Tail: Made of gas and dust that streams

from the head Form by solar wind and sunlight

pushing gas and dust away from the head

Tail always points away from the sun

Some tails can be more than 80 million km long

Comets

Oort cloud: Where most comets come from Named after the Dutch astronomer

Jan H. Oort Spherical cloud of dust and ice that

contains nuclei of comets Cloud surrounds the solar system

Starts at 1 ly from the sun Ends half way to the nearest star

From the beginning of the solar system; leftovers

Comets

Long-period comets: Have periods of several thousand or

million years Short period comets:

Have periods of up to 100 years Halley’s comet

Appears every 76 years Will appear again in 2062

Halley’s Comet

Meteoroids

Meteoroids: Smaller bits of rock or metal Most are less than 1 mm in

diameter From passing comets

Large pieces are from collisions with other meteoroids

Most burn up before they hit the ground

Shooting star (meteor) caused by friction of atmosphere

Fireball: vaporizes quickly

Meteoroids

Meteor shower: large amounts of meteoroids that come into the atmosphere at once Happen at the same time every year Earth passes through leftovers of

comets About 1 million kg of matter falls to

earth each day Meteorite: hits the ground;

makes it through the atmosphere Meteor Crater (Arizona) caused by a

large meteorite that hit

Meteoroids

Three types: Stony: like rocks on earth

Carbon substances Iron: have a metallic appearance Stony-iron: contain both types

Very rare

Can provide information about composition of the solar nebula

Iron Meteorite

Stony Meteorite

Dwarf Planets

Pluto

Pluto

Dwarf planet Discovered in 1930 by Clyde

Tombaugh, in Flagstaff, Arizona Diameter of 2,390 km

Smallest planet in the solar system Rotation rate = 6 days Orbital period = 250 years

Pluto

Has an elongated ellipse orbit Is sometimes inside Neptune’s orbit

Made of frozen methane, rock and ice

Average temp = -236 °C Has methane ice caps Has methane atmosphere

When it isn’t frozen

Pluto

Has one main moon = Charon Discovered in 1978 Appear to be a double planet system

Because they orbit so closely Found as an accident

Has two smaller moons orbiting it Nix and Hydra Between 50 – 60 km in diameter

Ceres

Has enough mass that its gravity causes it to be shaped like a sphere

Terrestrial – rocky Planet because

Orbits the sun Is round Not a moon

More Dwarf Planets

Makemake Third largest and

second brightest dwarf planet

Three quarters the size of Pluto

310 year orbital period

Made of methane, ethane and nitrogen ices

Eris Largest dwarf

planet in solar system – 27 % more massive than Pluto

Discovered in 2003 100 times farther

from Sun than Earth

Moon called Dysonmia

Orbits once every 16 days