2.______ holds galaxies together against the general expansion of the universe

3.The stars are too closely packed to get an accurate count, but it certainly has more stars than some of the ___ galaxies.

4. It is a cloud of gas and dust from which bodies in space are formed.

5. Whose astronomer able to resolve individual stars in several of the brighter spiral-shaped nebulae including M31?

6. What is the most distant object in the sky that the human eye can see without optical instruments?

7. How was Hubble able to determine the distances of nearby galaxies?

8. Who was the first astronomer to realize that the Milky way galaxy isn't motionless but rotates, and he calculated speeds at which stars at at various distances orbit around the galactic corner?

9.With a mass equal to that of four million suns, the ________, discovered in 1974, can be observed in the sky with radio telescopes close to the constellation Sagittarius. 

10. What is the supermassive blackhole at the center of Milky Way Galaxy?

11. How many local groups are in our Virgo Supercluster?

12. Galaxies that are unusual in their shape, size or composition and the result of the interactions between two galaxies.

13. These galaxies can be recognized by their wide, flat disks of rotating gas and dust.

14. This galaxy is known for being round, and can't form new stars.

15. Which is not a property of a peculiar galaxy.