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Stars and Galaxies

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Title: Stars and Galaxies


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  • Stars and Galaxies

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Constellations
  • Constellations- Certain groups of stars named
    after animals, characters in mythology, or
    familiar objects
  • From earth constellations look like groups of
    stars close together
  • Brightest star in the winter sky is Sirius
  • 88 constellations
  • Star Polaris North Star

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  • Appear to move because earth is moving
  • Stars also appear to change position in the sky
    throughout the year
  • Earth revolves around the sun
  • As earth orbits different constellations come
    into view while other disappear
  • Appendix j pg 674-675

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Absolute and Apparent Magnitudes
  • Absolute Magnitude
  • Is a measure of the amount of light is actually
    given off
  • Apparent Magnitude
  • Amount of light received on earth
  • Example Sirius 100x closer to earth then
    Rigel, therefore appears brighter

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Determining distances
  • Parallax
  • Apparent shift in the position of an object when
    viewed from two different positions
  • The nearer an object is to the observer, the
    greater its parallax
  • Distance in space are measures in light years
  • Light year is the distance light travels in 1
    year
  • Light travels at 300,000 km/s

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  • Nearest star other then the sun is Proxima
    Centuri
  • 4.2 light years away
  • It takes 4.2 years for light from that star to
    reach you
  • Stars temperature is determined by the color of
    the star

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  • Very hot stars blue white color
  • Cool stars orange or red
  • Stars temperature close to the sun yellow

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Evolution of Stars
  • H-R Diagram
  • Graph that shows relationship a stars temperature
    to its absolute magnitude
  • Most stars fit into the main sequence of stars
  • Hot blue bright stars (upper left)
  • Cool Red dim stars (lower right)
  • Sun is a yellow medium temp. star
  • 90 of all stars are Main Sequence

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  • The other 10 are Super Giants, Giants, White
    Dwarfs
  • Evolution of Stars
  • Stars begin as a large cloud of gas and dust
    called a nebula
  • At high temperature Fusion begins
  • Main sequence star forms
  • Begins to use its hydrogen

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  • When hydrogen fuel runs out, expands and becomes
    a giant
  • Core collapses
  • Outer portion of the giant blows away forming a
    white dwarf
  • Eventually the white dwarf uses its fuel and
    becomes a cold dead star
  • If a super giant (30 times our sun) collapses it
    may turn into a black hole

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Black Hole
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The Sun
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The Sun
  • 99 of all matter in our solar system is the sun
  • It is the center
  • Makes life possible on earth
  • Just an average star
  • Enormous ball of gas, fusing hydrogen into helium
    at its core

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  • Layers of the suns atmosphere
  • Photosphere
  • lowest layer from which light is given off
  • Temp. 6000 C
  • Chromosphere-
  • Upward about 6000 Km
  • Corona
  • Largest layer, extend out millions of km in space
  • Temp. 2, 000,000C
  • Charge particle escape causing solar wind

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  • Sunspots
  • Dark areas on the suns surface, which are cooler
    then their surroundings
  • Sun rotates
  • Rotates faster at its equator than at its poles
  • It takes 25 days for a sunspot to go around the
    sun at the equator

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  • Prominences and flares
  • Intense magnetic field associated with sunspots
    may cause prominence, huge arching columns of
    gases
  • So eruptive that material from the sun is blasted
    into space 1000 Km/sec

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  • Sun is a main sequence star
  • Most star are in a system in which two stars
    orbit each other (Binary system)
  • Our sun does not do this
  • Some stars move through space as star cluster

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Galaxies
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Galaxies
  • Large group of stars, gas, and dust held together
    by gravity
  • Galaxies are separated by huge distances, often
    millions of light years
  • Three types of galaxies
  • Elliptical
  • Spiral
  • Irregular

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Types of Galaxies
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  • Elliptical is the most common
  • Vary in size
  • Football shaped
  • Cluster of galaxies that the Milky Galaxy belongs
    to is called Local Groups
  • Spiral Galaxies have spiral arms
  • Milky Way is a spiral Galaxy

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  • Irregular Galaxies
  • Many different shapes
  • Cloud of Magellan Orbit

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Spiral
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Irregular
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Elliptical
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Milky Way Galaxy
  • In our galaxy, all stars orbit a central region
  • 200 million years for the sun to orbit this
    central region
  • Contains more then 200 billion stars

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Expansion of the Universe
  • When a Spectrograph is used to study light from
    galaxies beyond the Local group, there is a red
    shift in the light
  • Because there is a red shift in the light, all
    galaxies must be moving away from earth
  • Doppler Shift
  • Big Bang Theory states that between 15 and 20
    billion years ago, the universe began expanding
    out of an enormous explosion

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  • There is evidence that supports the Big Bang
    Theory
  • Scientist have discovered radiation in space
    that they believe was created by the explosion
  • All matter exerts a gravitational force
  • If there is enough matter, gravity will halt
    expansion
  • A big crunch would result

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Meteors
  • A meteoroid is matter revolving around the sun or
    any object in interplanetary space that is too
    small to be called an asteroid or a comet
  • A meteorite is a meteoroid that reaches the
    surface of the Earth without being completely
    vaporized
  • term meteor describe the streak of light produced
    as matter in the solar system falls into Earth's
    atmosphere creating temporary incandescence
    resulting from atmospheric friction.

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