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Chapter 21

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How does distance affect an image? Telescope- device that makes an object in the sky appear closer. Revolutionized astronomy (study of space)- allowed them to see objects in space for first time. Galileo made telescope famous seeing sun spots, Saturns rings, and Jupiters moons

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Electromagnetic Radiation There are waves of energy and light moving around us in the form of TV and radio transmissions, gamma radiation from space, and heat in the atmosphere. The waves of energy are called electromagnetic (EM) because they have both electric and magnetic characteristics.

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Electromagnetic Radiation They are classified by the frequency of their wavelength, going from high to low frequency. When a wave has a lot of energy, it could be a gamma ray or x-ray, and has high frequency. If it has low frequency, it has less energy and could be a TV or radio wave.

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http://video.pbs.org/video/2219781967/

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DETECTING ENERGY All types of EM radiation are useful to the world of science. Radio waves for example, They are used to carry communications from one point to another. Astronomers listen to the radio waves of other galaxies to learn more about their stars. Stars give off large amounts of EM radiation across the entire spectrum and we can study that radiation to learn more about the universe.

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Space Measurement Parallax- the apparent shift in position of an object when viewed from 2 separate positions Seen if you look at a star when Earth is at two different points during its orbit around the sun

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Scientists can measure the parallax of relatively close stars to determine their distance from Earth. Knowing the angle that the stars position changes and the size of the Earths orbit, we can calculate the distance of the star from Earth.

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Classifying Stars Color Temperature Size Composition Brightness

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Star Properties Color & temperature white / Hot stars Blue Yellow, orange, red / Cool stars

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Star Properties Size neutron- smallest white dwarf medium large giant/ super giant

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Star Properties Composition Use a spectrograph (breaks light into colors and produces an image) to detect elements Gases in a stars atmosphere absorb some of the wavelength of the light it produces Each Chemical element absorbs light

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Brightness How a star appears from Earth depends on the distance and the actual brightness of the star Actual brightness depends on size and temperature (absolute) Distance depends on how bright it appears (apparent)

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Star Magnitude (Brightness) Two types of magnitude Absolute Apparent

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Apparent magnitude brightness Measure of the amount of light received on Earth from a star. Brightness seen from Earth Both apparent and received have a r

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Absolute Magnitude Brightness The brightness the star would have at a standard distance from Earth. The total measure of the amount of light given off by a star. Total= absolute

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Light-year The distance between stars and galaxies in the universe is so vast it would be too much to describe it in miles or kilometerslike measuring the distance from New York to Tokyo in inches! Instead, scientists use light-years to measure distances in space.

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Light-year is actually a distance: the distance that light travels in one year. Light travels 186,000 miles per second which is equal to 300,000 km/s 9.5 trillion km/year

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Scientists can measure the parallax of relatively close stars to determine their distance from Earth. Knowing the angle that the stars position changes and the size of the Earths orbit, we can calculate the distance of the star from Earth. Space Measurement

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Parallax- the apparent shift or change in position of an object when you look from 2 different positions Seen if you look at a star when Earth is at two different points during its orbit around the sun

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if you stretch out your hand in front of you and look at your thumb while taking turns covering one eye and then the other, your thumb will appear to move back and forth. Stars do the same thing, but our eyes are much too close to see the difference. If we take a picture while on one side of Earth's orbit, and then take another when we get to the opposite side of the orbit, then we have a large enough distance that we can see the stars parallax, and determine how far away they really are.

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Parallax

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Classifying Stars Ejnar Hertzsprung and Henry Russell graphed stars by temperature and absolute magnitude in a H-R diagram Main Sequence Dwarfs Giants (Pg 722)

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Main sequence stars 90% fall on the diagonal band of the H-R diagram Stars in upper left of diagram graphs the hot, blue, bright stars Stars in lower right are cool, red, dim stars Stars in the middle are average, yellow stars like our sun

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Dwarfs and giants The 10% that fall outside the diagonal of the main sequence stars are dwarfs and giants

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Fusion The fusion of hydrogen in the core of star releases huge amounts of energy- atoms combine to form heavier atoms (2) HYDROGEN ATOMS SMASH and FUSE into HELIUM with a RELEASE of ENERGY

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A Star is Born All stars begin as a nebula (large cloud of gas and dust spread out in large volume)

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Nebula A nebula is a cloud of dust and gas, composed primarily of hydrogen (97%) and helium (3%). Within a nebula, there are varying regions when gravity causes this dust and gas to clump together. As these clumps gather more atoms (mass), their gravitational attraction to other atoms increases, pulling more atoms into the clump.

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Protostar Protostar- a contracting cloud of dust with enough mass to start formation of a star- fusion has not begun

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A star is born when the contracting gas and dust from a nebula become so dense and hot that nuclear fusion begins.

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The evolution of low mass stars Contracts and breaks apart instability caused by gravity Temperatures increase, particles get closer together Fusion begins Nebula Heat causes pressure that balances the attraction due to gravity Becomes a main sequence star Continues to use hydrogen fuel New Star Hydrogen in core depleted Core contracts and temperature inside increases Outer layers cool Core uses helium outer layers escape into space Leaves behind hot dense core now white dwarf Giant/White Dwarf

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High Mass Stars Nebula Main sequence SupergiantSupernova Neutron Star or Black Hole Recycling Matter Evolution quicker and more violent Core heats up quickly Core collapses violently and outer portion of star explodes Neutrons stars are collapsed core of supernovas; only neutrons exist in neutron star. Spinning neutron stars are pulsars Black hole form when supernova collapses to a point where no volume

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Black Holes http://coolcosmos.ipac.caltech.edu//cosmic_kids/AskKids/blackholes.shtml

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Clusters of stars Open Globular

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Open- loose, disorganized appearance containing no more than 1000 stars

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Globular- large groupings of older stars. Round and densely packed with stars. Some may contain more than a million stars

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Galaxies enormous swarms of stars, dust, gas, and dark matter held together by gravity. The sun is one of about 100 billion stars in our own galaxy, called the Milky Way. If you think thats incredible, imagine this: The Milky Way is just one of billions in the observable universe!

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Spiral Spiral galaxies are shaped like disks and look like pinwheels from above. Young stars are found in the arms, and older stars are found in the central bulge, or nucleus

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Elliptical galaxies Elliptical galaxies are the oldest and largest galaxies. They are smooth and oval and contain many old stars. There are many more elliptical galaxies in the universe than spiral galaxies

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Irregular galaxies Irregular galaxies dont have a distinct shape and are not symmetrical like spiral or elliptical galaxies. They may be young galaxies that have not yet formed a symmetrical shape, or their irregular shape may be caused by two galaxies colliding.

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The Universe within 50000 Light Years The Milky Way Galaxy

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Clusters of galaxies are often collected in super clusters. Our Milky Way is part of the Local Group and is part of the Virgo Super cluster, which contains several thousand galaxies.

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Milky Way Galaxy Classified as a normal spiral galaxy Contains more than 200 billion stars About 100,000 light years wide Sun orbits galaxys core every 240 million years

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Other planets around other stars? http://www.nasa.gov/multimedia/videogallery/index.ht ml?media_id=58885371 http://www.nasa.gov/multimedia/videogallery/index.ht ml?media_id=58885371

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Origins of the Universe How did the Universe begin? Where did we all come from? Has the Universe always been the same? Does the Universe change?

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Steady State Theory One theory is the Steady State Theory The universe has always been the same and will always stay the same Evidence suggests that this is not true though- indication are the universe was very different in the past.

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Oscillating Model A second idea is the Oscillating Model of the Universe. An expansion of the Universe began and everything moved outward. Over time, expansion slowed and the matter contracted back in. Process repeats itself over and over Works like a slinky

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Big Bang Theory Scientists accept this theory as more likely. We know the universe is expanding outwards About 12-15 billion years ago a giant explosion occurred The universe began to expand

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Big Bang Theory Within a fraction of a second, the universe grew from the size of a pinhead to 2000 times the size of the sun By the time the universe was one second old, it was a dense swirling mass of particles. Matter began to clump together, hydrogen and helium formed

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Big Bang Theory More than a billion years after the first explosion, the first stars were born.

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Origin of Universe Steady state theory Proposed the universe has always existed the same as it is now Oscillating model Universe began with expansion occurring in all areas of universe- expansion slowed, matter contracted, and process began again. Big Bang Theory The universe began with an enormous explosion.

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Our Expanding Universe The Doppler Shift explains how we know the Universe is expanding. If a star is moving towards Earth, the light wavelengths are compressed and you would see the spectrum in blue If a star is moving away from Earth, the light wavelengths are stretched out and you see the spectrum in red.

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The Red Shift- Hubble Law In 1929, Edwin Hubble published a paper about light from other galaxies. In 1929, Edwin Hubble published a paper about light from other galaxies. All galaxies beyond the Local Group (our group of galaxies) show a red shift in their spectrum, this shows they are moving away from us. The Universe is expanding. All galaxies beyond the Local Group (our group of galaxies) show a red shift in their spectrum, this shows they are moving away from us. The Universe is expanding.

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Dark energy In the late 1990s astronomers observed the expansion of the universe appeared to be accelerating. Galaxies seemed to be moving apart at a faster rate now than in the past. No know force to account for it which they now call dark energy.

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http://hubblesite.org/hubble_discoveries/dark_energy / http://hubblesite.org/hubble_discoveries/dark_energy /

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Looking Back in Time EXPLAIN THIS!!!!!!!!!