The Milky Way

1
The Milky Way

• Elise Peters
• The Big Bang and Beyond
• November 21st, 2003

2
What is it?

• The Milky Way is a galaxy of at least 200 billion
  stars which our sun and solar system are a part
  of.
• It is seen as a broad band of light, but if it
  was not blocked by the horizon, it would look
  like a circle around the sky.

3
Beginnings of the Milky Way

• Some evidence suggests that the Milky Way can
  into being by the collapse of a vast gas cloud.
• New information has led researchers to think that
  several gas cloud fragments merged to create the
  protogalactic Milky Way and then collapsed.
• Many astronomers use what they know about the
  chemical composition of stars to find out more
  about how the Milky Way came into existence.

4
Who discovered the Milky Way?

• Bertil Lindblad of Sweden and Jan Oort of
  Netherlands hypothesized that the Milky Way
  system is a flattened rotating galaxy.
• John Plaskett and Joseph Pearce accumulated three
  decades worth of data on stellar motions that
  confirmed the Lindblad-Oort picture.

5
Structure and Components

• Three main components
• Extended dark halo of stars and unknown
  composition
• thin disk of young and middle aged stars
• Central bulge

6
More Structure and Classification

• The Milky Way is a spiral galaxy which means that
  it
• 1- a flat, large disk made of interstellar
  matter
• 2-young star clusters which are either
  Population
• 1 or Population 2
• It is classified now as Sb, but more recent
  investigations show that it might be an
  intermediate type between barred and normal
  spirals. (These classifications have to do with
  the relative size of nuclear bulges and the
  degree to which the spiral arms coil.)

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The halo of the Milky Way

• The halo is a spherical region centered around
  the nucleus and containing old stars, in groups
  called globular clusters.
• The halo has a radius of about 5000 light years.
• One place where we see evidence for dark matter.

8
The Disk of the Milky Way

• Has spiral arms, which
• contain billions of matter
• or antimatter stars,
• planets, and galactic
• dust and gas
• 10,000 light years in
• thick and 100,000 light
• years in diameter

9
The Central Bulge of Milky Way

• The boundary between the galaxy disk,
  comprising the arms and inter-arm dust lanes.
• Commonly referred to as the luminous mound in the
  middle of a galaxy that would be left if the disk
  was not there
• Most of the light from the bulge is contained
  within a radius of about 1500 light-years from
  the galactic center.
• An interesting recent discovery is that the bulge
  is in the shape of a bar (twice as long as it is
  wide). The long axis points almost at our Suns
  position in the disk.

10
The Galactic Center and our
Position in the Milky Way

• The galactic center is the common center of
  gravity around which all the objects in the Milky
  Way Galaxy orbit.
• Our sun is about 26000 light years from the
  center of the Milky Way Galaxy
• We are on one of the spiral arms towards the
  edge.

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How do we see the Milky Way?

• No actual pictures of the Milky Way because we
  can stand on the outside of our galaxy and look
  at it.
• We can however look at other galaxies that are
  similar to ours to learn about our own. The one
  shown here is NGC2997.

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Why is the Milky Way important to ME?

• Our sun and solar system are located in the Milky
  Way and the future of the Milky Way directly
  relates to our future.
• Also knowledge of what is around us makes us
  realize that we are not the only planet and that
  there is possibility of other life.

13
The Future of the Milky Way

• Astronomers have found luminous material to the
  side of NGC 4874, which is one of the super
  massive elliptical galaxies at the core. This
  material suggests tidal disruptions of one galaxy
  by another and the reason is not yet known.
• There is another dwarf spherical galaxy orbiting
  the Milky Way at almost the same distance from
  the center as our solar system. Astronomers are
  not sure if this galaxy will eventually gather up
  many of the stars of our Milky Way for its own or
  if it will gradually fall apart.
• Almost all of the existing gas will be consumed
  in a few billion years. Then no more stars will
  form and the disks of spirals will fade and the
  galaxy will consist of only white dwarfs, black
  holes, and dark matter.

14
The Candy Bar

• The Milky Way candy bar developed in the Midway
  district between Minneapolis and St. Paul by
  confectioner Frank C. Mars, 39, is a mixture of
  milk chocolate, corn syrup, sugar, milk,
  hydrogenated vegetable oil, cocoa, butter, salt,
  malt, egg whites, etc. Inspired perhaps by his
  own astronomical name, Mars names his creation
  after the distant star galaxy.
• Three parts like Milky Way
• -Chocolate-? Halo
• -Carmel-? Disk
• -Nougat? Central Bulge

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Sources

• Levy, David.
• 2000. The Scientific American Book of Cosmos.
  St. Martins Press New York.
• Belkora, Leila
• 2003. Minding the Heavens. Institute of Physics
  Publications Bristol.
• http//www.seds.org/messier/more/mw.html
• http//referenceallrefer.com/encyclopedia/M/MilkyW
  ay.html
• http//www.enchantedlearning.com/subjects/astronom
  y/solarsystem/where.shtml
• http//www.star.le.ac.uk/edu/mway/
• http//map.gsfc.nasa.gov/m_uni/uni_101mw.html