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HOW WAS THE UNIVERSE FORMED? • The BIG BANG THEORY states that billions of years ago the universe exploded and expanding energy became matter over time. WHAT IS A GALAXY? • A collection of billions of stars, gas, and dust that orbit each other around a center. • They are not all the same size. Some may be 20 LY across, some may be 100 LY across. WHAT IS A GALAXY? • Stars in galaxies revolve around the center of the galaxy (like planets around the sun). • Scientists believe at the center of each galaxy is a black hole. WHAT ARE THE 3 TYPES OF GALAXIES? 1.Spiral 2.Elliptical 3.Irregular WHAT IS A SPIRAL GALAXY? • Shaped like a pinwheel. It usually has a large, flat disk. • Contain a lot of interstellar matter (gas and dust) and young star clusters. WHAT IS A SPIRAL GALAXY? • Rotates clockwise around the center. • Our sun is one of several 100 billion stars in a spiral galaxy, the Milky Way • Spiral galaxies can also be barred. WHAT GALAXY IS OUR SOLAR SYSTEM IN? Our sun and solar system is in the Milky Way Galaxy in the Orion Arm WHAT IS AN ELLIPTICAL GALAXY? • Elliptical galaxies are oval in shape • They do not rotate • Contain very little or no gas and dust (interstellar matter). • Consists mainly of old stars. No new stars are forming. WHAT IS AN IRREGULAR GALAXY? • No definite shape (contains star clusters, clouds, dust and gas). • Not very common • Often due to distortion by the gravitation of other galaxies. WHAT IS A STAR? • A bright, hot, dense ball of gas (hydrogen and helium) held together by its own gravity. • Stars radiate light and heat and are the only source of light in the universe. WHAT IS NUCLEAR FUSION? • Stars create energy in the form of light and heat through nuclear fusion. • Hydrogen is the main component of stars. Hydrogen fuses with another Hydrogen to create Helium and release energy. H + H He HOW ARE DISTANCES BETWEEN STARS MEASURED? • Distances between stars are measured in light years. • 1 light year = the distance light travels in 1 year. Light is the fastest thing in the Universe. • The speed of light = 300,000 km/sec That’s 9,467,280,000,000 km/year (9 ½ trillion). STARS AND THEIR DISTANCES FROM EARTH • Alpha Centauri………………………………4 light years • Sirius………………………………………………8 light years • Polaris (north star)……………………..400 light years • Andromeda galaxy……………………….2 million light years WHAT IS THE SUN? • What are the Parts of a Star? Radiative Zone Chromosphere Convective Zone Corona Photosphere Sun Spot Core Solar Flare PARTS OF THE SUN (THE INTERIOR) 1. Core: The center of the sun. Where fusion occurs and the sun’s energy is produced. 2. Radiative Zone: Very dense region. 3. Convective Zone: Gases circulate in convection currents. Hot gases sink and cool gases rise. PARTS OF THE SUN (THE ATMOSPHERE) 4. Photosphere: Surface of the sun. Where light radiates (photo = light) 5. Chromosphere: thin region below the corona. Gives the star its color (chromo = color) Only visible during a total solar eclipse. 6. Corona: The sun’s outer atmosphere. WHAT LAYER OF THE SUN IS ONLY VISIBLE DURING A SOLAR ECLIPSE? • FEATURES OF THE SUN • Sun Spot: dark, cooler areas on the sun that move around every 11 years. Usually in pairs. Sunspot up close…it’s way bigger than the Earth FEATURES ON THE SUNS SURFACE • Prominence: Loop extending from the sun’s photosphere. Link sunspots together. • Solar Flare: Explosion extending from connected sun spots. Releases large amounts of energy. HOW ARE STARS CLASSIFIED? • Size (magnitude) • Temperature • Color WHAT IS A HERTZPRUNGRUSSEL DIAGRAM • Luminosity (brightness) increases from bottom to top. Brightness is affected by the temperature of the star • Temperature increases from right to left. Temperature depends on the elements of the star-what is the star made of. • Magnitude (size) increases from bottom to top. H-R DIAGRAM Luminosity (brightness) 100,000 10,000 1,000 1 1/100 1/10,000 Increasing Temperature HOW DOES THE TEMPERATURE OF A STAR RELATE TO ITS COLOR? H-R DIAGRAM STARS STARS • The life cycle of a star! Star Life Cycle Nebula Large, dense, cloud of interstellar dust (like carbon) and gas (mostly H and He). This is the area where stars are born. Star Life Cycle Protostar A baby star. Gravity pulls gases together, it contracts into a clump of matter and becomes more dense. When hot enough, it starts nuclear fusion and the star is born. Star Life Cycle Main Sequence Most of a stars life. Smaller cooler stars are on the right, bigger hotter stars on the left. Hotter stars have very short life span, cooler stars have a long life span. Star Life Cycle GIANT Low mass stars become giants. The star runs out of hydrogen, the core shrinks and the outer layers expand. Starts to cool down. SUPERGIANT High mass stars become supergiants. The star runs out of hydrogen, the core shrinks and the outer layers expand. Starts to cool down. Star Life Cycle White Dwarf Red giant looses its atmosphere leaving a small, very hot core. These are old stars about to die. Our sun will become a white dwarf. What is a Star’s life cycle? Neutron Star High mass supergiants may undergo a supernova, where the core suddenly collapses and explodes. A neutron star is what remains after the supernova. It is composed mainly of neutrons and is very dense. If it spins and releases radiation it is called a pulsar. What is a Star’s life cycle? Black Hole The biggest mass stars (10-1,000,000 times the sun) will undergo a supernova and will contract into a black hole. It is not really a hole. It has so much gravity that not even light can escape it. They can not be seen directly. STARS • Stars have long lives compared to us STARS SO LET’S SEE IF LIGHT CHANGES DUE TO COMPOSITION!!! ELECTROMAGNETIC SPECTRUM BY TEMPERATURE Radio • Radio • Microwave Gamma less than 3K 3 to 30K Cool • Outer Space • Infrared 30 to 4100K • Humans • Visible 4100 to 7300K • Our star! • UV 7300 to 3,000,000K • Hottest Stars • X-ray • Gamma Ray Hot 3,000,000 to 300,000,000K beyond 300,000,000K ELECTROMAGNETIC SPECTRUM • Light travels in the universe and atmospheres absorb wavelengths • We can figure out what elements the star is made of by the color of it’s wavelength. H hydrogen