Stars and Galaxies

1
Stars and Galaxies
Created by the Lunar and Planetary Institute For
Educational Use Only LPI is not responsible for
the ways in which this powerpoint may be used or
altered.

• Space Science for Middle School at HCDE
• February 20, 2009

Image at http//hubblesite.org/newscenter/archive/
releases/galaxy/spiral/2009/07/image/g/results/50/

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Welcome!

• Please complete the pre-assessment
• Its for usits not about you
• Please let us know how much YOU know, not how
  much your friends sitting next to you know

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What are we going to cover?

• Our Place in the Universe
• The Electromagnetic Spectrum
• Classifying Stars
• Classifying Galaxies
• History of the Universe

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First up

• Our Place in the Universe
• What is our Universe made of?
• How big are things? How far away?
• How do we know?

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What is our Universe made of?
What was in your drawing?

• Stars and planets
• Gas and dust
• Organized into star clusters
• Organized into nebulae
• Organized into galaxies
• Other things
• Black holes
• Dark matter
• Dark energy

Image from http//galileo.rice.edu/lib/student_wor
k/astronomy95/orionpleiades.html
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Activity!!

• Use the Venn diagrams to place the stickerswhere
  does everything go?
• After youre finished, lets discuss

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Examining the Components

• Stars
• Gas and dust (Nebulae)
• Star clusters
• Galaxies

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Different types of stars
Image from http//hubblesite.org/newscenter/archiv
e/releases/star20cluster/globular/2003/21/image/a
/results/50/
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Types of Stars

• Big
• Small
• Red
• Blue
• Yellow
• In groups
• Alone
• More later

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What is a star cluster?

• stars formed together at same time
• stars may be gravitationally bound together
• two types open (galactic) and globular

Image at http//hubblesite.org/newscenter/archive/
releases/star20cluster/globular/2007/18/image/a/f
ormat/web/results/50/
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Open Clusters

• dozens to thousands of stars
• young stars! only a few million years old
• may still be surrounded by nebula from which they
  formed
• located in the spiral arms of a galaxy
• example Pleiades

Image at http//hubblesite.org/newscenter/archive/
releases/star20cluster/open/2004/20/image/a/resul
ts/50/
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More open star clusters
Image from http//hubblesite.org/newscenter/archiv
e/releases/star20cluster/open/2006/17/image/a/res
ults/50/
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Globular Clusters

• millions to hundreds of millions of stars
• old! 6 to 13 billion years
• mostly red giants and dwarfs
• stars are clumped closely together, especially
  near the center of the cluster (densely)
• surround our disk as a halo

Image at http//hubblesite.org/newscenter/archive/
releases/star20cluster/globular/1999/26/image/a/r
esults/50/
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What is a nebula?

• A cloud in space
• Made of gas and dust
• Can have stars inside
• Most of the ones we see are inside our Milky Way
  Galaxy
• Different types

Orion image at http//hubblesite.org/newscenter/ar
chive/releases/2006/01/image/a/results/50/
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Large, massive, bright nebulae

• Emission Nebula
• The hot gas is emitting light

Orion image at http//hubblesite.org/newscenter/ar
chive/releases/2006/01/image/a/results/50/
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Colder, darker nebulae
Dark dust blocking the hot gas behind it
NOAO/AURA/NSF Image from http//hubblesite.org/new
scenter/archive/releases/nebula/dark/2001/12/image
/c/results/50/
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Leftovers from an Explosion
Supernova remnant (smaller, less gas)
Image at http//hubblesite.org/newscenter/archive/
releases/nebula/supernova-remnant/2005/37/results/
50/
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What is a galaxy?

• A large group of stars outside of our own Milky
  Way
• Made of billions to trillions of stars
• Also may have gas and dust
• Spiral, or elliptical, or irregular shaped

Image at http//hubblesite.org/newscenter/archive/
releases/galaxy/spiral/2007/41/results/50/
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Spiral galaxy--Andromeda
NOAO/AURA/NSF Images at http//www.noao.edu/image_
gallery/html/im0606.html and http//www.noao.edu/i
mage_gallery/html/im0685.html
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Elliptical Galaxies
Images at http//hubblesite.org/newscenter/archive
/releases/galaxy/elliptical/2007/08/image/a/format
/large_web/results/50/ and http//hubblesite.org/n
ewscenter/archive/releases/galaxy/elliptical/1995/
07/results/50/
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Irregular Galaxies
NASA and NOAO/AURA/NSF Images at
http//hubblesite.org/newscenter/archive/releases/
galaxy/irregular/2005/09/results/50/ ,
http//www.noao.edu/image_gallery/html/im0560.html
, and http//www.noao.edu/image_gallery/html/im09
93.html
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Our Galaxy the Milky Way

• has about 200 billion stars, and lots of gas and
  dust
• is a barred-spiral (we think)
• about 100,000 light-years wide
• our Sun is halfway to the edge, revolving at half
  a million miles per hour around the center of the
  Galaxy
• takes our Solar System about 200 million years to
  revolve once around our galaxy

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The Milky Way
Image at http//news.nationalgeographic.com/news/b
igphotos/1945371.html
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Mapping the Milky Way
How do we know what our Galaxy looks like?

• We can see stars
• star clusters
• nebulae
• Galaxies
• Lets try to Map our Galaxy

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Measuring Distances

• Parallax (lets model it)
• As Earth orbits the Sun, we see nearby stars move
  relative to more distant stars
• How many degrees did the plate move, relative to
  the background?
• Can you calculate the distance to the plate?
• Sine of the parallax (angle) x Earths distance
  to the Sun Distance to the star
• The angles involved for strellar observations are
  very small and difficult to measure. Proxima
  Centauri, has a parallax of 0.77 arcsec. This
  angle is approximately the angle subtended by an
  object about 2 centimeters in diameter located
  about 5.3 kilometers away.

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Measuring Distances

• What is a Light Year?
• A light year is the distance light travels in a
  year. Light moves at a velocity of about 300,000
  kilometers (km) each second how far would it
  move in a year?
• About 10 trillion km (or about 6 trillion miles).
• Why do we use light years?
• Show me how far 5 centimeters is.
• Now show me 50 centimeters.
• Now tell me (without thinking about it, or
  calculating it in meters) how far 500 centemeters
  is. 2000? 20,000?
• We need numbers that make sense to us in
  relationship to objects we scale up and use
  meters and kilometers for large numbers.

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Time for a Break! Next Up

• Our Place in the Universe
• The Electromagnetic Spectrum
• Classifying Stars
• Classifying Galaxies
• History of the Universe

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Lets check your knowledge

• Please draw an electromagnetic spectrum on a
  sheet of paper, and label the parts.
• You can work in groups.

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Radiation

• There are lots of types of light (radiation),
  including visible and invisible

Electromagnetic spectrum http//coolcosmos.ipac.c
altech.edu/cosmic_classroom/ir_tutorial/what_is_ir
.html .
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Lets Observe A Spectrum

• What will the spectrum look like with a red
  filter in front of your eyes? A blue filter?
• Hypothesize and test your hypothesis.
• Now lets examine the invisible partsusing our
  cell phones and a solar cell.

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• There are different types of spectra
• Continuous
• Emission or Bright Line (from ionized gas, like a
  nebula or a neon sign)
• Absorption or dark line (from stars)

Illustration at http//imagine.gsfc.nasa.gov/docs/
science/how_l1/spectra.html
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Radiation

• All stars emit radiation
• Radio, infrared, visible, ultraviolet, x-ray and
  even some gamma rays
• Most sunlight is yellow-green visible light or
  close to it

The Sun at X-ray wavelengths Image at
http//imagine.gsfc.nasa.gov/docs/science/know_l1/
sun.html
Image and info at http//imagine.gsfc.nasa.gov/doc
s/teachers/gammaraybursts/imagine/page18.html
.
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Using a Stars Spectrum

• We can use a stars spectrum to classify it.

NOAO/AURA/NSF image at http//antwrp.gsfc.nasa.gov
/apod/ap010530.html
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Stellar Evolution
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Time to Create a Stellar Graph

• Everyone will receive several stars
• Place them on the large paper, according to their
  color and their brightness
• This is a version of the Hertzsprung-Russell
  diagram.

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Hertzsprung-Russell Diagram
Images from http//www.nasa.gov/centers/goddard/ne
ws/topstory/2007/spectrum_plants.html and
http//sunearthday.gsfc.nasa.gov/2009/TTT/65_surfa
cetemp.php
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Young stars form in nebulaefrom Small
Magellanic Cloud
Image at http//hubblesite.org/newscenter/archive/
releases/2007/04/image/a/results/50/
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Star-forming region in the Large Magellanic
Cloud http//hubblesite.org/newscenter/archive/re
leases/2008/31/image/a/results/50/
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Orion image at http//hubblesite.org/newscenter/ar
chive/releases/2006/01/image/a/results/50/
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Interstellar eggs
Movie at http//www.stsci.edu/EPA/PR/95/44/M16.mpg

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Our Sun is a Regular/ Small Star
On the Main Sequence
Image at http//www.gsfc.nasa.gov/topstory/2001121
0insidesun.html
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In a few Billion years Red Giant
Image at http//hubblesite.org/newscenter/archive/
releases/1997/26/image/a/
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Our Suns Habitable Zone

• Billions of years ago, things may have been
  different
• The Sun was cooler (by up to 30!)
• Earths atmosphere was different (thicker, carbon
  dioxide)
• Conditions will be different in the future
• By many accounts, increases in the Suns
  temperature will make Earth uninhabitable in 1
  billion years or less
• These changes will also affect other planets
  Mars?

Animation at http//www.nasa.gov/97994main_BHabita
bleZone.MPG
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By 5 billion years White Dwarf
Small, but very hot
Image at http//hubblesite.org/newscenter/archive/
releases/nebula/planetary/1998/39/results/50/
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Image at http//hubblesite.org/newscenter/archive/
releases/nebula/planetary/2000/28/image/a/format/w
eb_print/results/50/
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Image at http//hubblesite.org/newscenter/archive/
releases/nebula/planetary/2004/27/image/a/format/l
arge_web/results/50/
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Massive Stars are different
On the Main Sequence but not for long
Image from http//hubblesite.org/newscenter/archiv
e/releases/nebula/emission/1997/33/results/50/
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BetelgeuseRed Supergiant
Image from http//hubblesite.org/newscenter/archiv
e/releases/star/massive20star/1996/04/image/a/res
ults/50/
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SupernovaMassive Star Explodes
Images at http//hubblesite.org/newscenter/archive
/releases/star/supernova/2004/09/results/50/
http//hubblesite.org/newscenter/archive/releases/
nebula/supernova-remnant/2005/37/results/50/ http
//chandra.harvard.edu/photo/2009/casa/
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Neutron Star or Pulsar
Image at http//hubblesite.org/newscenter/archive/
releases/nebula/supernova-remnant/2002/24/results/
50/
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Black Hole
Image at http//hubblesite.org/newscenter/archive/
releases/2002/30/image/a/results/50/
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Classifying Galaxies
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Galaxies

• come in different sizes (dwarf, large, giant)
• come in different shapes and classifications
• Spirals
• Ellipticals
• Lenticulars
• Irregulars
• are fairly close together, relative to their sizes

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Spiral Galaxies

• have flat disk, spiral arms, central bulge, and a
  surrounding halo
• some have a barred bulge
• are fairly large (no dwarf spirals)
• have lots of gas and dust and younger stars in
  their arms, but older stars and little gas or
  dust in their halos and central bulges

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Galaxies
Image at http//hubblesite.org/newscenter/archive/
releases/galaxy/spiral/2005/01/results/50/
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Spiral galaxy--Andromeda
NOAO/AURA/NSF Images at http//www.noao.edu/image_
gallery/html/im0606.html and http//www.noao.edu/i
mage_gallery/html/im0685.html
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Spiral Galaxy on Edge
Image at http//hubblesite.org/newscenter/archive/
releases/galaxy/spiral/2006/24/image/a/results/50/

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Image at http//hubblesite.org/newscenter/archive/
releases/galaxy/spiral/2007/41/results/50/
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Elliptical galaxies

• range from spherical to football shaped
• range from very small to giant
• have very little gas or dust
• mostly old stars
• similar to the central bulge of a spiral galaxy

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Elliptical Galaxies
Images at http//hubblesite.org/newscenter/archive
/releases/galaxy/elliptical/2007/08/image/a/format
/large_web/results/50/ and http//hubblesite.org/n
ewscenter/archive/releases/galaxy/elliptical/1995/
07/results/50/
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Lenticular

• have a disk but no arms
• have little or no excess gas and dust

Image at http//hubblesite.org/newscenter/archive/
releases/galaxy/elliptical/2002/07/results/50/
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Irregular Galaxies

• any galaxy that isnt a Spiral, Elliptical, or
  Lenticular
• usually have lots of gas and dust and young stars
• may have a distorted shape from interaction with
  another galaxy

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Irregular Galaxies
NASA and NOAO/AURA/NSF Images at
http//hubblesite.org/newscenter/archive/releases/
galaxy/irregular/2005/09/results/50/ ,
http//www.noao.edu/image_gallery/html/im0560.html
, and http//www.noao.edu/image_gallery/html/im09
93.html
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Collisions!

• We now think that galaxies in groups and clusters
  often collide
• The Milky Way is moving at 300,000 mph toward the
  Andromeda Galaxy
• They may collide in about 5 billion years
• Stars dont usually collide
• New orbits, gas piles up to form new stars

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Interacting
Image from http//hubblesite.org/newscenter/archiv
e/releases/galaxy/interacting/2000/34/results/50/
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the Antennae or Mice
Information at http//hubblesite.org/newscenter/ar
chive/releases/galaxy/interacting/1997/34/results/
50/
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The occasional results of two galaxies colliding
ringed galaxies
Images from http//hubblesite.org/newscenter/archi
ve/releases/galaxy/spiral/2002/21/image/a/results/
50/ and http//hubblesite.org/newscenter/archive/r
eleases/galaxy/spiral/1999/16/image/a/results/50/
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Various galaxies (can you identify types?)
Image at http//hubblesite.org/newscenter/archive/
releases/galaxy/cluster/1999/31/results/50/
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Supermassive black holes

• almost every medium to large galaxy weve check
  has a supermassive black hole at the center
• the larger the galaxy, the more massive the black
  hole
• we dont know which comes first, the galaxy or
  the black hole
• we think that these black holes are responsible
  for some of the galaxies with jets and lobes
  which give off radio waves, x-rays, etc.

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Active galaxy
Image at http//hubblesite.org/newscenter/archive/
releases/galaxy/spiral/2000/37/results/50/
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at the center of a large galaxy
Image at http//hubblesite.org/newscenter/archive/
releases/exotic/black-hole/1998/22/results/20/
and http//hubblesite.org/newscenter/archive/relea
ses/exotic/black20hole/2000/21/image/a/format/web
_print/results/20/
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Galaxy Clusters

• the Local Group
• includes the Milky Way, the Andromeda, and over
  30 other smaller galaxies
• the Virgo Cluster
• hundreds to thousands of galaxies, 60 million
  light-years away
• giant elliptical at center, formed by galactic
  cannibalism
• the Local Group is falling toward the Virgo
  Cluster at 60 to 250 miles per second!

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Coma Cluster
Image at http//hubblesite.org/newscenter/archive/
releases/galaxy/cluster/2008/24/image/a/results/20
/
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Superclusters!

• clusters are bound together in larger structures,
  called superclusters
• these superclusters have been mapped, and are
  grouped into long strings
• 300 million to a billion light-years long
• 100 to 300 million light-years wide
• and only 10 to 30 million light-years thick
• in between these strings are huge voids of
  galaxies, although some astronomers may have
  detected hot gas

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Evolution of Galaxies
Image at http//www.galex.caltech.edu/media/glx200
7-05f_img01.html
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Origin of the Universe

• Big Bang
• Dominant scientific theory about the origin of
  the universe
• Occurred 13.7 billion years ago
• What is the Big Bang?
• How do we know?

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What is the Big Bang?

• Infinitely dense point not governed by our
  physical laws or time
• All matter and energy contained in one point

Image from http//www.newscientist.com/articleimag
es/dn11799/0-did-antimatter-factory-spark-brightes
t-supernova.html
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Building a Universe

• Instantaneous filling of space with all matter

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History of the Universe

• 10-43 seconds - gravity separates from other
  forces
• 10-35 to 10-32 seconds - fundamental particles -
  quarks and electrons
• 10-6 seconds - quarks combine into protons and
  neutrons
• 1 second - electromagnetic and weak nuclear
  forces separate
• 3 minutes - protons and neutrons combine into
  atomic nuclei
• 105 years - electrons join nuclei to make atoms
  light is emitted
• 105-109 years - matter collapses into clouds,
  making galaxies and stars

Orion Nebula - http//stardate.utexas.edu/resource
s/ssguide/planet_form.html
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History of the Universe
Image from http//dsc.discovery.com/space/top-10/s
trange-universe/space-10-weirdest-things-universe-
10.html
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Later History
Image at http//www.galex.caltech.edu/media/glx200
4-01r_img02.html
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Big Bang Theory

• In 1915, Albert Einstein concluded that the
  universe could not be static based on his
  recently-discovered theory of relativity and
  added a "cosmological constant" to the theory of
  relativity because astronomers assured him that
  the universe was static
• Aleksandr Friedmann and Abbe George LeMaitre are
  credited with developing the basics of the Big
  Bang model between 1922 and 1927 their
  calculations suggested that universe is
  expanding, not static.
• Years later, Einstein called his cosmological
  constant the biggest mistake of his career

Image at http//map.gsfc.nasa.gov/universe/bb_theo
ry.html
83
Expanding Universe

• In 1929, Edwin Hubble showed that most galaxies
  are red-shifted (moving away from us), and that a
  galaxys velocity is proportional to its distance
  (galaxies that are twice as far from us move
  twice as fast)

Image from http//imagine.gsfc.nasa.gov/docs/scien
ce/mysteries_l1/origin_destiny.html
84
Hubbles Evidence

• Doppler shifting - wavelength emitted by
  something moving away from us is shifted to a
  lower frequency
• Sound of a fire truck siren - pitch of the siren
  is higher as the fire truck moves towards you,
  and lower as it moves away from you
• Visible wavelengths emitted by objects moving
  away from us are shifted towards the red part of
  the visible spectrum
• The faster they move away from us, the more they
  are redshifted. Thus, redshift is a reasonable
  way to measure the speed of an object.
• When we observe the redshift of galaxies, almost
  every galaxy appears to be moving away from us
  the Universe is expanding.

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Predictions for the Big Bang Model

• The expansion of the Universe Redshifting
• Edwin Hubble's 1929 observation that galaxies
  were generally receding from us provided the
  first clue that the Big Bang theory might be
  right.
• The abundance of the light elements H, He, Li
• The Big Bang theory predicts that these light
  elements should have been fused from protons and
  neutrons in the first few minutes after the Big
  Bang.
• The cosmic microwave background (CMB) radiation
• The early universe should have been very hot. The
  cosmic microwave background radiation is the
  remnant heat leftover from the Big Bang.

86
Evidence for Big Bang

• Red shift - as light from distant galaxies
  approach earth there is an increase of space
  between earth and the galaxy, which leads to
  wavelengths being stretched
• In 1964, Arno Penzias and Robert Wilson,
  discovered a noise of extraterrestrial origin
  that came from all directions at once - radiation
  left over from the Big Bang
• In June 1995, scientists detected helium in the
  far reaches of the universe - consistent with an
  important aspect of the Big Bang theory that a
  mixture of hydrogen (75) and helium (25) was
  created at the beginning of the universe

87
When Did the Universe Form?

• 13.7 billion years ago
• How do we know?
• Spreading (Red Shift) - know distances, rates of
  retreat, relative positions
• Pervasive background radiation of 2.7C above
  absolute zero - afterglow of the Big Bang

Cosmic background radiation temperature on
celestial sphere
http//timeline.aps.org/APS/resources/85_06a.jpg
88
Feedback, Questions

• Reach us online at http//www.lpi.usra.edu/educati
  on/
• For more information, contact
• Christine ShuplaLunar and Planetary
  Institute3600 Bay Area BlvdHouston, TX 
  77058(281) 486-2135shupla_at_lpi.usra.edu