Now lets move on to factorizations that may | Ch 6.5 - 58

Chapter 19: Our Galaxy  The Milky Way Revealed o What does our galaxy look like  Dusty and gas obscure our view of the galaxy.  Looks like a disk  100,000 light-years in diameter  Bulge in the middle  Globular Clusters in the halo o Halo is outside the disk  Has spiral arms: different color from bulge o Blueish: bigger, younger stars  Barred Spiral  The bulge is elongated like a bar is in it. o How do stars orbit in our galaxy  Stars in the disk travel in circles with little up and down motions  Halo stars go above the disk randomly  Bulge stars move in random paths  We have a 230 million-year orbit  Orbital Velocity Law  The orbital speed and radius of an object on a circular orbit around the galaxy tells us the mass within that orbit.  Galactic Recycling o How is gas recycled in our galaxy  Star-Gas-Star Cycle n o Wh er dIonization nebulae are found around short-lived high-mass stars  Shows star activity  None in halo, or bugle o No stars being formed  Reflection nebulae scatters the light from stars  Spiral Arms of the galaxy is where most of the star formation takes place  History of the Milky Way o What clues to our galaxy’s history do halo stars hold  Halo Stars are older than our galaxy  Formed first then stopped o Giant cloud makes the halo stars are it contracts.  Center of our galaxy o What lies in the center of our galaxy  Lots of stars orbit around it  We believe it is a black hole  Lots of mass  Invisible  Small Region  See X-ray bursts, but no accretion disk l