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Stars Our sun is a star! Solar Prominence Solar Flare Total Eclipse Partial Eclipse Solar Eclipse: Moon blocking the sun We are going to go BIG: Universe • All of Space and everything in it •Includes billions of galaxies! Galaxy • A cluster of millions or billions of stars What Galaxy do we live in??? • The Milky Way!!! • There are billions of other galaxies in the universe. • There is a lot of empty space between galaxies There are billions of Galaxies in the Universe. Some are very small with only a few million stars. While others could have as many as 400 billion stars, or even more. One of the deepest images of the sky taken to date with NASA's Hubble Space Telescope reveals a population of faint blue galaxies. This cluster of galaxies can be found in the constellation Draco, some 2 billion lightyears from Earth. This is a galaxy. This is a galaxy. This is a galaxy. Vocabulary GALAXY - a huge group of stars, dust, gas, and other celestial bodies bound together by gravitational forces. Kinds of Galaxies There are three kinds of Galaxies, Spiral, Elliptical, and Irregular. The only difference between the three is what shape they are. Elliptical Spiral Irregular Draw and label the three different types of galaxies. Spiral galaxies are galaxies whose main component is a flat disk with a central bulge from which several arms wind their way around the center toward the rim. Spiral Galaxy #M109 Spiral Galaxies are like a plate, so they look flat from the side,. The Andromeda Galaxy is the closest major galaxy to the Milky Way, and the farthest object that can be seen with the naked eye. It is about 2,400,000 light-years from Earth, so it takes 2.4 million years for the light from there to reach us! An irregular galaxy is a galaxy with no symmetry. Irregular galaxies get their odd shapes in many ways. One way irregular galaxies are formed is when galaxies collide or come close to one another, and their gravitational forces interact. Can you name each galaxy? SPIRAL 1. __________ ELLIPTICAL IRREGULAR 3. __________ 2. __________ Vocabulary SPIRAL GALAXY - flat disk with a central bulge from which several arms radiate. ELLIPTICAL GALAXY – smooth, elliptical/round shape. IRREGULAR GALAXY – no symmetry, no patterns. Galaxies often crash into one another. Even our own galaxy has had others pass right through it. Don't worry though, galaxies can pass through each other quite safely. Stars are so far apart that the chances of two colliding is very unlikely. THE MILKY WAY GALAXY The Milky Way as seen from Earth Milky Way Galaxy Our Solar System is located in the far reaches of a spiral galaxy that we call the Milky Way Galaxy. Almost all of the stars that we see in the night sky are also members of the Milky Way Galaxy. The Milky Way Galaxy contains roughly 200 billion stars, one of which is our Sun. What type of galaxy is the Milky Way? Irregular Spiral Elliptical The correct answer is… Spiral What is a Solar System? • One star and everything that orbits the star. • Our solar system has the sun, 8 planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Neptune), Pluto and possibly other dwarf planets, and asteroids. Our solar system: 8 Planets and the Sun Light-Year • The distance light travels in one year • Unit of Distance Fun Fact: • It takes a little over 8 minutes for light from out sun to reach Earth. • The light you see in the sky left the sun 8 minutes before you looked! • Light from other stars will take many years (Even Millions of years!) to reach us, so when you look at stars you are really looking into the past! Parallax • Apparent Change in position of an object when you look at it from different places. Click for parallax animation… • http://instruct1.cit.cornell.edu/courses/astr o101/java/parallax/parallax.html • The more a star moves, the closer it is to Earth! How Stars are Classified • Size • Temperature • Brightness A Star’s Brightness is Determined in 2 Ways: • Apparent Magnitude • Absolute Magnitude Apparent Magnitude • A star’s brightness as seen from Earth. • Stars that are closer to Earth look brighter. Absolute Magnitude • The brightness a star would have if it were a standard distance from Earth. Hertzsprung-Russell Diagram • H-R Diagram • A graph comparing the brightness and temperature of stars. Brightness Temperature in Kelvins H-R Diagram: • When you graph Temperature (Star Color) and Brightness of many stars, you get patterns. • Astronomers have studied the patterns on the graph and have learned many things about stars. A Star is Born! • Stars are formed in nebulas. • A nebula is a huge cloud of dust and gas somewhere in space. Lagoon Nebula Orion Nebula Eagle Nebula Inside the Nebula… • Gravity pulls some of the gas and dust together into a clump. • As the clump gets bigger, it starts getting hot. Inside the Nebula… • After many millions of years the clump is big enough and hot enough for nuclear fusion. • Nuclear fusion: When atoms are so hot and moving so fast they melt together and release energy. • You can see some of the energy as light and feel heat! Nuclear Fusion: • Most stars are made of hydrogen atoms. • When 2 hydrogen atoms fuse together they make a new atom of helium. A star is born… • When a star first gives off energy it is called a protostar. • As it fuses atoms together it is a main sequence star. –90% of the stars you see in the sky are main sequence stars. • As the star runs out of fuel, it will grow larger and cooler and become a Red Giant. (Cool, dim) –Huge stars with lots of fuel can become a Supergiant – It is like taking the wood from a burning campfire and spreading it out across the beach. It gets cooler and dim, but takes up more space. A Star Dies… • Red giants made from small and medium stars will slowly lose their outer layer of gas. • The fuel that is left will be in a hot core that will shine as a white dwarf. (Small, hot star) A Star Dies… • Red giants made from large stars may explode into a supernova. – Some of the star pieces may form a new nebula, which starts the cycle over again. A Star Dies… • Most stars that go supernova will leave behind a neutron star, which is only about 20 km across but very dense. • Neutron stars give off radio waves! • A few huge stars will become a black hole: –The matter left from the explosion gets packed really tightly, so it is very dense. –This very dense matter has so much gravity not even light can escape. –It is about 30km across, but 5 times more mass than the sun. How long do stars shine? • It depends on the mass of the star: –Bigger stars have more mass and burn fuel faster. (Like big trucks) –Smaller stars use less fuel (Like cars) So: The bigger the star, the sooner it runs out of fuel and dies! How do scientists know this??? • Astronomers have looked at many different stars, some very old and some very young. • They make graphs to compare the stars color, size, and what kind of atoms they are made of. (Like the H-R diagram) • They use this data to make conclusions. The sun is our star… • The sun is a medium-mass star, so it will NOT go supernova. • Medium-mass stars live for about 10 billion years. • Our sun is about 4.6 billion years old right now, so it is ½ way through its life. Origin of the Universe: • Scientists believe the universe we see today began with a giant explosion called the big bang. • Astronomers estimate the universe is 10-15 billion years old. Why do they think this??? • All the galaxies and stars we see are moving away from us at top speed, just like pieces of something that exploded. –There is more data, such as background radiation and other calculations that fit this theory. Big Bang How did our Solar System get here? • The big bang left dust and gas in nebulas. • The gravity between the dust made it spin around and come together into clumps. • A very large clump in the center became the sun. How did our Solar System get here? • Smaller clumps of matter spinning around the sun became planets. • The 4 inner planets lost most of their gas because they were too hot. (Mercury, Venus, Earth, Mars) • The 4 outer planets became gas giants. (Pluto, Saturn, Uranus, Neptune) Our solar system: 8 Planets and the Sun