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Bellwork Review Questions: Ch 4 1. What is a planet and how is it formed? (think of the video we watched “How Universe was Made”) 2. How do we know how the solar system formed? 3. What does an astronomical unit measure? 4. Why is Pluto now considered a Dwarf Planet? The Moon A look at our nearest neighbor in Space! LESSON 2 Free powerpoints at http://www.worldofteaching.com What is the Moon? • A natural satellite • One of more than 96 moons in our Solar System • The only moon of the planet Earth Location, location, location! • About 384,000 km (240,000 miles) from Earth • 3,468 km (2,155 miles) in diameter (about ¼ the size of Earth) The Moon’s Surface • No atmosphere • No liquid water • Extreme temperatures – Daytime = 130C (265°F) – Nighttime = -190C (-310 F) • 1/6 Earth’s gravity Lunar Features - Highlands • Mountains up to 7500 m (25,000 ft) tall • Rilles (trenchlike valleys) Lunar Features - Craters • Up to 2500 km (1,553 miles) across • Most formed by meteorite impact on the Moon • Some formed by volcanic action inside the Moon Lunar Features - Maria • Originally thought to be “seas” by early astronomers • Darkest parts of lunar landscape • Filled by lava after crash of huge meteorites on lunar surface 3-4 billion years ago • Mostly basalt rock Craters Can you see the rays? Maria Does this photo show us a limb or terminator line? Movements of the Moon • Revolution – Moon orbits the Earth every 271/3 days • The moon rises in the east and sets in the west • The moon rises and sets 50 minutes later each day • Rotation – Moon turns on its axis every 27 days • Same side of Moon always faces Earth Craters Name these features. Maria Name these features. Kuiper Belt _______________ Oort Cloud National Aeronautics and Educational Product Space Administration Teachers Grades 5-12 Exploring Meteorite Mysteries Slide Set with Script Larger meteorites are extremely rare, but make enormous craters when they hit the Earth It was formed about 50,000 years ago when a large iron meteorite hit the Earth Scientists estimate that the meteorite weighed one million tons Meteor Crater in Arizona is over one kilometer across and 150 meters deep Although people have seen meteorites fall since the earliest times, it was only about 1800 when scientists finally became convinced that rocks really did fall from the sky Since then, we've discovered that most meteorites come from the asteroid belt, the area of the solar system between the orbits of Mars and Jupiter where many asteroids orbit the sun Asteroids are small planets, fragments of rock and iron left over from the formation of the solar system or the breakup of larger fragments Many asteroids probably look like Ida, the asteroid in this picture taken by the Galileo spacecraft in 1993 Ida is about 30 kilometers long, is made of rock, and has many craters Comets are small bodies made of rock, dust and ice, formed in the distant reaches of the solar system Then solar radiation heats the comet's surface, causing part of the ice to boil off into space and carry some of the dust with it When this happens the comet can develop a "tail" millions of kilometers long, and leave a dust trail behind in solar orbit Formation of the Solar System It began with a Nebular Gas Cloud From which developed Proto-Sun & Planets From which came the Sun, Planets, & Debris Which finally cleared out to leave just the Sun & Planets (and their moons, etc.) Rocky Matter (Source of craters) Debris Icy Matter (Source of comets) Icy Matter ... Jan Oort’s Cometary Cloud Most comets that we see today are believed to have come from the Oort cloud. Why do you suppose they leave the cloud in the first place? Coma May be 1000’s of km Nucleus - Few 10’s of km The Head of a Comet The Tail of a Comet Larger meteorit es don't come from comets but from asteroid It's a long way from the asteroid belt to the Earth Very few asteroid pieces get the chance to travel that far Most asteroids never do, and spend eternity in space, Every now and again the orbits of asteroids cross and their quiet times end Then the asteroids collide and shatter, and the pieces fly into different orbits around the sun Eventually some of their orbits cross the Earth's orbit, and the piece of asteroid can hit the Earth Some of these pieces orbit closer and closer to the sun We see this moving flame as a meteor crossing the sky If the asteroid fragment is big enough, fist-sized or so, it won't burn up completely and will fall to the Earth as a meteorite These small meteorites do not explode or make craters when they hit They just hit like an extra large hailstone or a rock thrown from across the street Meteorites have also had devastating effects on life... The dinosaurs were killed 65 million years ago after a huge meteorite hit the Earth The explosion caused great storms and waves, and the sky was dark for months with dust and ash The dinosaurs, along with many other animals and plants, were probably killed by the climate changes that followed the explosion Inner Planets Outer Planets What are rings? What is an orbit? Describe the shape of an orbit.