Amber Reed's Notes

Chapter 14

What does our galaxy look like?
-our galaxy look like?
- our galaxy consists of a disk of stars and gas, with a bulge of stars at the center of the disk, surrounded by large spherical halo

How do stars orbit in our galaxy?
-Stars in the disk orbit in circles going in the same direction with a little up and down motion
-orbits of halo and bulge stars have random orientations

How is gas recycled in our galaxy?
-gas from dying star mixes new elements into the interstellar medium, which slowly cools, making the molecular clouds where stars form
-Those stars will eventually return much of their matter to interstellar space

Where do stars tend form in our galaxy?
-Active star forming regions contain molecular clouds, hot stars and ionization nebulae 
-Much of the star formation in our galaxy happens in the spiral arms

What do halo stars tell us about our galaxy's history?
-Halo stars are all old, with a smaller proportion of heavy elements than disk stars, indicating that the halo formed first

How did our galaxy form?
-our galaxy formed from the huge cloud of gas, with the halo stars forming first and the disk stars forming later, after the gas settled into a spinning disk

What lies in the center of our galaxy?
-Orbits of the stars near the center of our galaxy indicate that it contains a black hole with 4 million times the mass of the Sun