the milky way galaxy
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
The Milky Way GalaxyPg. 131
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 Scientists began by mapping globular
clusters Saw they were located above and
below the plane of the galactic disk
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.
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
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
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
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
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
Draw a rough sketch of the Milky Way galaxy and include the following (you may look up a picture of the galaxy on your phone or computer):• the spiral arms• Put a circle where the halo would be. • Draw stars to represent the globular clusters• Put a filled in circle where the nucleus and the
nuclear bulge would be. • Where would the younger stars be located?• Where would the Population II stars be?
Pg. 46