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The Milky Way Galaxy

The Milky Way Galaxy. Pg. 45. The Milky Way Galaxy. A disk made of stars orbiting a central point Perhaps 100 billion stars in the milky way. Discovering the Milky Way. Difficult to see because we are inside of it Can’t tell how big it is, where the center is or where Earth is in it

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The Milky Way Galaxy

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  1. The Milky Way Galaxy Pg. 45

  2. The Milky Way Galaxy A disk made of stars orbiting a central point Perhaps 100 billion stars in the milky way

  3. Discovering the Milky Way Difficult to see because we are inside of it Can’t tell how big it is, where the center is or where Earth is in it Scientists began by mapping globular clusters Saw they were located above and below the plane of the galactic disk

  4. Galactic Center The center of a galaxy is a region of very high star density The direction of the galactic center is toward the constellation Sagittarius.

  5. The shape of the Milky Way Use radio waves to map it Can penetrate interstellar gas and dust Center is called the nucleus Has a bulge that sticks out of the disk Halo (spherical region where clusters are found) exists outside the nucleus

  6. Spiral arms of the milky way Scientists use Hydrogen to discover the spiral arms Our Sun is located in the minor arm Orion (28000 ly away from the center) Approximated the sun has orbited the center about 20 times

  7. Mass of the Milky Way About 100 billion times the mass of the sun 90% of mass contained in the halo Some matter can’t be seen (neutron stars, black holes, white dwarfs) Called black matter

  8. Stars in the Milky Way Halo contains the oldest known objects in the galaxy, globular clusters About 99.9% of the stars are hydrogen and helium Young stars are located in the spiral arms Can be broken into 2 regions: stars in the halo and bulge; stars in the disk (esp. spiral arms) Population I stars are in the disk and arms and contain some heavy elements (our Sun) Population II stars in the halo and bulge that contain hardly any heavy elements

  9. Formation and evolution of the Milky Way Galaxy began as a spherical cloud in space Cloud eventually collapsed under the force of its own gravity Rotation forced it into a disk Spiral arms are maintained by a spiral density wave (dense and less dense regions that are frozen and rotate in a rigid pattern) May also be continually forming because of supernova explosions

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