Stars and Galaxies

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Stars and Galaxies
Created by the Lunar and Planetary Institute For
Educational Use Only
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/