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Study Guide Module 2

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Big Bang : Scientific theory of how the universe started. All matter in the universe was once a single point. Gravity and energy may have caused the matter to expand The universe is still expanding After the Big Bang, the universe contained pockets of dust. Law of Universal Gravitation: that all objects attract each other. All objects that have mass attract each other. Objects with large masses (like planets and some stars) have a large amount of attraction Small objects like people, houses, and cars have a very small amount of attraction Explosion of great force Dust and clouds appear Tightly packed dust cloud form planet or star Clouds and dust pull towards each other in a spiral

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Stars start out in a giant nursery called a Nebulae Then gravity pulls all the dust and gas together until the pull is soo strong it forms a ball, this can take millions of years! Then as the pressure and mass increase, the heat increases too! Soon it gets so hot it goes through nuclear fusion, where the atoms in the dust and gas form helium and poww!~ a star is born!

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Stars + Stars + Stars + planets = the Universe! Its Huge!! Our Galaxy is called the Milky Way. It is a spiral galaxy and contains billions of stars! Eventually the gravitational pull of our Sun (a main sequence star) pulled all the newly formed planets, comets, etc into orbit around it. And so our galaxy was born! The Milky Way is said to have around 100,000,000,000 stars! And there are 100,000,000,000 other galaxies in the Universe. That leaves the universe with trillions and trillions of stars! Many scientists estimate that the universe has 400,000,000,000,000,000,000,000 stars.

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A galaxy is a group of stars, planets, gas, and dust that is held together by gravity. There are three different types of galaxies: TypeShapeGas/Dust contentAge IrregularNo real shapeContain lots of gas and dust Young SpiralRevolve around single point Some gas and dust Middle EllipticalCircular and concentrated Little to no gas and dust Older

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Speed of Light: light travels 800,000 times faster than sound. In fact, light is the fastest thing in the universe that we know of! Light travels: Around the Earth in 0.13 sec To the Moon in 1.3 sec. To the Sun in 8 min. The nearest Star to Earth is Proxima Centauri. It takes light 4.2 years to travel from the star to our eyes! This means that 4 years ago the star could have exploded and we would have no idea!

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A light year is the distance that light can travel in one year. So if an object is one light year away, it will take light one year to get there. 1 light year = 9,461,000,000,000 km or 5,879,000,000,000 miles Light years are used to measure distances in space because their large size allows us to talk about vast distances using smaller numbers. For example, it is 20,000,000,000 light years to the edge of the universe which equals 117,580,000,000,000,000,000,000 miles!

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Brightness Scientists use four different characteristics to help them classify and describe stars. Temperature - Determines the color of the star Cold = red, warm = yellow, Hot = white, Super hot = blue Star composition - Provides a "fingerprint" for stars. Most common elements are hydrogen and helium Star Brightness - Is determined by star size, distance away, and strength of light Apparent Magnitude- The brightness of a star as it appears from the earth, without the effect of the earths atmosphere Absolute Magnitude- the actual amount of light that a star gives off. (brightness) Star Size Neutron, medium, giant and supergiant, Dwarf Size Composition Temperature

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Y axis = Stars Absolute Magnitude X axis = Stars temperature When we compare the absolute magnitude and temperature of stars, we will see that the brighter a star is, the hotter it will be. The main reason that the HR Diagram is so useful is you can tell the size of the star by plotting it on the graph. The different sizes of stars form a pattern. The HR diagram is a scatter graph used by scientists to study the stars. The graph shows the relationship between the stars' absolute magnitudes versus their temperatures (C).

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TypeSizeSurface temperature BrightnessWeightDetails NeutronSmallVery HighDullHeavy : 1tbs = 10 tons! Tight and compact DwarfSame as EarthHighLittle to no light Less than the sun Half the weight of a neutron Medium-Size (main sequence) Same as the Sun! Average Moderate/Aver age Most stars are in this category Giant10-100 times larger than sun LowBrightVery bigBecomes a dwarf when it dies Supergiant1000 times larger than sun LowVery BrightLargest in universe Becomes a black hole when it dies Types of Stars!

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Stars are formed, mature, and eventually cease to function as stars!

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There are two tracks a star can take in its life Or

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A black hole is formed when a supergiant star dies and are hard for scientists to study because they are black and hard to see. Mass causes gravity. The more mass an object has, the more gravity it applies. Now, imagine an astronomical object so massive that its gravity becomes large enough to crush itself into a small volume. The gravity of this object would be so large that even light, the fastest moving phenomenon in the universe would not be fast enough to break free of the pull. Since light cannot escape from it, it would not be possible to see the object. The object would pull in all the light around it and so appear black. Stars have very high mass and therefore very high gravitational pull. The atoms of a star undergo nuclear reactions and release huge amounts of energy. The gravity of a star pulls the matter forming the star towards its center while the energy from nuclear reactions pushes the matter out. These two forces are in balance. Eventually, the matter undergoing nuclear reactions runs out. If this core contains enough mass, the structure of the atoms forming the core breaks under the high gravity and the core collapses into a black hole. Thus, black holes form when very high concentrations of mass are squeezed in a small volume.

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High mass stars will not live as long as low mass stars. The high mass stars will be hotter and brighter. Because of this they will burn through their fuel faster and die sooner. Small mass stars will live for 100 billion years. Average mass stars will live for 10 billion years. Large mass stars will live for 5 billion years or less.

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1) Solar prominences are flame-like arcs into space, which are associated with sunspots and magnetic fields. Some solar prominences last for many days, others for only minutes. 5) The chromosphere is the middle layer atmosphere of the sun. Temperatures in the chromospheres average more than 25,000 C. The photosphere is considered the surface of the sun. Temperatures in the photosphere are usually around 6,000 C. 2) Solar Flares- Flares, of all solar events, are the shortestlasting only minutes..(pause).. and the most violent creating a fusion explosion equal to millions of hydrogen bombs. The explosion of a solar flare is so violent that, like an earth quake, pressure waves race across the entire immense surface of the sun in just a few hours.

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4) Corona-The corona is the outermost part of the suns atmosphere. The temperature of the corona exceeds one million C and can only be seen during an eclipse, where the moon covers up the sun leaving only the corona exposed, or through a special solar telescope. 3) Sunspots- Dark regions on the suns surface where the temperature within the spot is lower than the rest of the sun. These cooler spots come and go and can be effect earth. When there are a large number of sunspots, the magnetic activity that comes from these sunspots can disrupt communication systems on earth. Cell phones, radios, and TV antennas will not work as well.

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The electromagnetic spectrum is the range for light shown in the graph below. We can only see a very small range of actual light due to the frequency of the light waves. Sound waves are different from light waves and are not found on the graph. Sound waves require matter to travel through, where light does not.

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The range of colors we see are the frequencies visible to our eyes. DID you know!? Ultra-Violet frequencies are visible to insects and snakes can sense infra-red waves! If you combine all frequencies they will appear as white light, which is just the same as black being the absence of light. The non-absorbed frequency that is reflected by the object is what we see and how we get different colors.

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Light does not travel in a perfectly straight line but moves like a wave in the ocean. There are two important properties of waves that determine the type of light. Wavelength: distance between two crests. Frequency: Number of times a wave crest passes by a point in one second.

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Wavelength and Frequency are Related if you change the wavelength of a wave it will affect the frequency, if you change the frequency of a wave it will affect the wavelength.

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Types of light can be determined by studying the wavelength and frequency of the light.

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Light has a fingerprint called an emission spectrum. When an atom lets off or emits light it does not let off just one color. It emits a combination of a few colors. The emission spectrum is all the colors that the atom emits. Here is the emission spectrum for iron. Spectrometer are the instruments that scientists use to see the atoms emission spectrum. They take the light and bend it through a prism to break them down into their colors.

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Stars and planets are made up of many different atoms. When scientists pass the light coming from the star or planet through the spectrometer they get an emission spectrum. They then analyze the emission spectrum to see which atom's individual light fingerprints are in there. In this way, they can use the light from stars and planets to find out what the star or planet is made of.

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Types of light emission fingerprints: White Light White light is light that contains every color of the rainbow. Notice that every color is in white lights emission spectrum. Hydrogen Hydrogens spectrum has some different shades of violet, some shades of blue and a red. Hydrogen is the most abundant element in the universe. Sodium Sodiums spectrum contains two shades of yellow. Helium Helium is another very abundant element in the universe. Heliums spectrum contains some different shades of blues, a yellow and a red. Neon Neon is the atom that is contained in a neon light. Can you see why a neon light looks orange? Mercury Mercurys spectrum contains purple, blue, green and two shades of yellow.

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Be sure to review: The Big Bang Theory. The parts of the universe. The distances in the universe. The properties of stars. HR diagrams. The stages of a star's life. The physical appearance of the sun. The characteristics of the electromagnetic spectrum. How the electromagnetic spectrum is used to study stars and planets.

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Module Vocabulary Absolute MagnitudeEmission SpectrumProxima Centauri Apparent MagnitudeFrequencySolar Flare BetelgeuseGalaxySolar Prominence Chromosphere Law of Universal Gravitation Spectrometer Big BangNebulaProtostar Fusion IgnitionMain SequenceGiant Super GiantsDwarfBlack hole NeutronIrregular GalaxyElliptical Galaxy Spiral GalaxyLight YearSpeed of light Milky WayPhotosphereSunspot CoronaWavelengthFrequency