Chapter 14 Quiz: Olivia Ward

1. What does our galaxy look like?
   
   To us, the Milky Way appears to be a faint band of light in the sky. It consists of a thin disk about 100,000 light-years in diameter. This disk contains most of the gas and dust of the interstellar medium.
   
2. How do stars orbit in our galaxy?
   
   All of the stars in the disk orbit the galactic center in the same direction. Halo and bulge stars also orbit the center of the galaxy, although their orbits are randomly inclined to the disk of the galaxy.
   
3. How is gas recycled in our galaxy?
   
   Our galaxy's gas is recycled through the star-gas-star cycle. This cycle recycles gas from old stars into new star systems: atomic hydrogen clouds → molecular clouds → star formation → nuclear fusion in stars → returning gas → hot bubbles → cycle repeats
   
4. Where do stars tend to form in our galaxy?
   
   Much of the galaxy's star formation takes place in the disk because of the ionization nebulae. More specifically, this process most often occurs in the spiral arms. The gas clouds get squeezed as they move into the spiral arms, which triggers star formation. The young stars then flow out of the spiral arms.
   
   
5. What do halo stars tell us about our galaxy's history?
   
   The halo is the home to older low-mass stars that have smaller amounts of heavier elements than the stars in the disk. Halo stars must have formed early in the galaxy's history, before the gas settled into the a disk.
   
   
6. How did our galaxy form?
   
   Halo stars probably formed in protogalactic clouds of hydrogen and helium. Gravity pulled the clouds together to form a larger one. The collapse of this cloud continued until it formed a spinning disk around the galactic center. Stars have continued to form in the disk.
   
7. What lies in the center of our galaxy?
   
   Star movement near the center of the galaxy suggest that there is a black hole about 4 million times as massive as the Sun.
   
8.  Who is Andrea M. Ghez?
   
   She is an astronomer and professor at UCLA who has studied star-forming regions and the super-massive black hole of the Milky Way.
   
9. Who observed stars moving close to the speed of light in the center of our galaxy?
   
   Dr. Andrea Ghez made these observations.
   
10. Where was Dr. Ghez born?
    
    Dr. Ghez was born in New York City, but grew up in Chicago.