Galaxies and the Milky Way

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Galaxies and the Milky Way
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1. One light year 1 ly distance light travels
in 1 year
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2. Galaxy large group of stars, gas and dust
held together by gravity
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3. Estimate 40 billion galaxies can be seen.
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4. Three types of galaxies spiralelliptical
and irregular
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Spiral galaxy spiral arms and large central
round mass of stars
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Barred spiral central mass of stars oblong,
not round
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Elliptical galaxy
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Elliptical galaxies are 3 dimensional ,
egg-shaped
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Irregular
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Irregular galaxy uncommon, no distinct shape
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5) MOST common type galaxy dwarf elliptical
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6. Milky Way spiral galaxy of400 billion stars
including the Sun
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Visible Examples of elliptical large and small
clouds of Magellan
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7. Local group cluster of 45 galaxies near the
Milky Way.
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8. Andromeda Galaxy largest galaxy in Local
Group
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9. Galaxies are moving.Separate stars in
galaxies are also moving.
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10. If galaxies collide stars so far
apart,most stars will just glide past each
other . http//www.youtube.com/watch?vWuucxy7snB
sfeaturerelmfu
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11. Dwarf galaxy colliding with large galaxy may
be absorbed
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12. Milky Way has already absorbed some dwarf
galaxies.No problemhttp//astroaviator.com/2009
/09/08/milky-way-and-the-dwarf/
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13. But Milky Way and Andromeda Galaxy will
collide within 5 billion years
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v
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OOPS
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14. How galaxies form gravity
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Remember Milky Waycontains 400 billion stars
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15. Sun orbits around center of Milky Way
every 225 million years
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How many times has Sun orbited since it formed?
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22 times
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16. All of the stars we can see belong to the
Milky Way.
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17. structure of Milky Way spiral
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18. Sun is 26,000 light years from center of
Milky Way
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19. Spiral arms contain young stars and
protostars and nebulae
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20 Stars form on the spiral arms
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21. We believe the center of the galaxy is a
supermassive black hole.
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Big Bang Theory
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Cosmology
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22. Cosmology is study of the universe.
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Models of the universe
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23. 1920s Oscillating model of universe
big bang and big crunch
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a) Universe expanded rapidly, slowed, and then
contracted.
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b) The universe continues cycle of expand and
contract .
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24.1948Steady state theory a) universe has
always existed and always will.
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b) As universe expands, new matter is created.
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c)The density of the universe is constant.
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25. Current theory Big Bang Theory
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a) Universe began as very hot, and very densely
packed matter
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b) The matter exploded, expanded rapidly, and
cooled.
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c) Matter did NOT expand into space, space
itself expanded.
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d) Space continues to expand.
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26. Universe is 13.7 billion years old
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27. Relative motion of stars in the Milky Way
detected by Doppler Effect
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Remember wavelengthRed light l 700 nm
longer than blue light l 400 nm
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Doppler effect each star emits a constant
wavelength of light star color
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If star NOT moving relative to an observer,
observed wavelength is constant
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28.If star is moving away from observer,
wavelength appears longer Red Shift
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29. If star is moving towards observer,
wavelength appears shorter. BLUE SHIFT
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31. HUBBLE RED SHIFTFor distant galaxies, red
shift caused because Universe is expanding.
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31. The Universe contains Visible mostly
hydrogen matter and Invisible dark matter
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32.Very small percent of matter is ordinary
visible matter.
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33.Majority of matter and energy in universe is
dark matter and dark energy.
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34. Einstein equation E mc2relates energy
and mass
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35 Universe is expanding AND accelerating
because of dark energy
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36. gravity has less effect as Universe expands,
so matter accelerates apart