Chapter 3 Solar System Section 4 Asteroids, Comets and Meteoroids Notes 3-6

Asteroids Largest of the small bodies in the solar system Largest of the small bodies in the solar system Fragments of rock that orbit the sun Fragments of rock that orbit the sun Orbits are ellipses Orbits are ellipses Ceres is found in the asteroid belt but is now called a dwarf planet. Ceres is found in the asteroid belt but is now called a dwarf planet. About 1,000 km in diameter About 1,000 km in diameter

Asteroids Asteroid Belt Asteroid Belt Region between Mars and Jupiter Region between Mars and Jupiter Most asteroids can be found there Most asteroids can be found there Begins around 100 million km beyond Mars’ orbit and continues for 150 million km toward Jupiter Begins around 100 million km beyond Mars’ orbit and continues for 150 million km toward Jupiter Classified according to composition Classified according to composition Carbon: gives a dark appearance Carbon: gives a dark appearance Iron and nickel: have a metallic look Iron and nickel: have a metallic look Silicate minerals: most are this; look like earth rocks 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 Believed that these are the remains of planetesimals that didn’t not form a planet Mostly because of Jupiter’s strong gravitational force Mostly because of Jupiter’s strong gravitational force Trojan Asteroids: are also called earth- grazers Trojan Asteroids: are also called earth- grazers Orbit the sun but are not in the asteroid belt Orbit the sun but are not in the asteroid belt Found around Jupiter Found around Jupiter Occasionally they do collide with Earth Occasionally they do collide with Earth

Comets Comet: Comet: Body of rock, dust, methane, ammonia and ice Body of rock, dust, methane, ammonia and ice Nucleus: made of rock, metals and ice Nucleus: made of rock, metals and ice Around 1km to 100 km in diameter Around 1km to 100 km in diameter Orbit the sun in long ellipses Orbit the sun in long ellipses Cloud of gas and dust is called the coma Cloud of gas and dust is called the coma Nucleus and coma form the head of the comet Nucleus and coma form the head of the comet Bright appearance is from light reflecting off of it Bright appearance is from light reflecting off of it

Comets Tail: Tail: Made of gas and dust that streams from the head Made of gas and dust that streams from the head Form by solar wind and sunlight pushing gas and dust away from the head Form by solar wind and sunlight pushing gas and dust away from the head Tail always points away from the sun Tail always points away from the sun Some tails can be more than 80 million km long Some tails can be more than 80 million km long

Comets Oort cloud: Oort cloud: Where most comets come from Where most comets come from Named after the Dutch astronomer Jan H. Oort Named after the Dutch astronomer Jan H. Oort Spherical cloud of dust and ice that contains nuclei of comets Spherical cloud of dust and ice that contains nuclei of comets Cloud surrounds the solar system Cloud surrounds the solar system Starts at 1 ly from the sun Starts at 1 ly from the sun Ends half way to the nearest star Ends half way to the nearest star From the beginning of the solar system; leftovers From the beginning of the solar system; leftovers

Comets Long-period comets: Long-period comets: Have periods of several thousand or million years Have periods of several thousand or million years Short period comets: Short period comets: Have periods of up to 100 years Have periods of up to 100 years Halley’s comet Halley’s comet Appears every 76 years Appears every 76 years Will appear again in 2062 Will appear again in 2062

Halley’s Comet

Meteoroids Meteoroids: Meteoroids: Smaller bits of rock or metal Smaller bits of rock or metal Most are less than 1 mm in diameter Most are less than 1 mm in diameter From passing comets From passing comets Large pieces are from collisions with other meteoroids Large pieces are from collisions with other meteoroids Most burn up before they hit the ground Most burn up before they hit the ground Shooting star (meteor) caused by friction of atmosphere Shooting star (meteor) caused by friction of atmosphere Fireball: vaporizes quickly Fireball: vaporizes quickly

Meteoroids Meteor shower: large amounts of meteoroids that come into the atmosphere at once Meteor shower: large amounts of meteoroids that come into the atmosphere at once Happen at the same time every year Happen at the same time every year Earth passes through leftovers of comets Earth passes through leftovers of comets About 1 million kg of matter falls to earth each day About 1 million kg of matter falls to earth each day Meteorite: hits the ground; makes it through the atmosphere Meteorite: hits the ground; makes it through the atmosphere Meteor Crater (Arizona) caused by a large meteorite that hit Meteor Crater (Arizona) caused by a large meteorite that hit

Meteoroids Three types: Three types: Stony: like rocks on earth Stony: like rocks on earth Carbon substances Carbon substances Iron: have a metallic appearance Iron: have a metallic appearance Stony-iron: contain both types Stony-iron: contain both types Very rare Very rare Can provide information about composition of the solar nebula Can provide information about composition of the solar nebula

Iron Meteorite

Stony Meteorite

Dwarf Planets

Pluto

Pluto Dwarf planet Dwarf planet Discovered in 1930 by Clyde Tombaugh, in Flagstaff, Arizona Discovered in 1930 by Clyde Tombaugh, in Flagstaff, Arizona Diameter of 2,390 km Diameter of 2,390 km Smallest planet in the solar system Smallest planet in the solar system Rotation rate = 6 days Rotation rate = 6 days Orbital period = 250 years Orbital period = 250 years

Pluto Has an elongated ellipse orbit Has an elongated ellipse orbit Is sometimes inside Neptune’s orbit Is sometimes inside Neptune’s orbit Made of frozen methane, rock and ice Made of frozen methane, rock and ice Average temp = -236 °C Average temp = -236 °C Has methane ice caps Has methane ice caps Has methane atmosphere Has methane atmosphere When it isn’t frozen When it isn’t frozen

Pluto Has one main moon = Charon Has one main moon = Charon Discovered in 1978 Discovered in 1978 Appear to be a double planet system Appear to be a double planet system Because they orbit so closely Because they orbit so closely Found as an accident Found as an accident Has two smaller moons orbiting it Has two smaller moons orbiting it Nix and Hydra Nix and Hydra Between 50 – 60 km in diameter Between 50 – 60 km in diameter

Ceres Has enough mass that its gravity causes it to be shaped like a sphere Has enough mass that its gravity causes it to be shaped like a sphere Terrestrial – rocky Terrestrial – rocky Planet because Planet because Orbits the sun Orbits the sun Is round Is round Not a moon Not a moon

More Dwarf Planets Makemake Makemake Third largest and second brightest dwarf planet Third largest and second brightest dwarf planet Three quarters the size of Pluto Three quarters the size of Pluto 310 year orbital period 310 year orbital period Made of methane, ethane and nitrogen ices Made of methane, ethane and nitrogen ices Eris Largest dwarf planet in solar system – 27 % more massive than Pluto Discovered in times farther from Sun than Earth Moon called Dysonmia Orbits once every 16 days