6. What is a galaxy?
a) A planet
b) A star
c) A system of millions or billions of stars, along with gas and dust, held together by gravity
d) A black hole
7. What is a supernova?
a) A planet that explodes
b) A star that explodes
c) A galaxy that explodes
d) A black hole that explodes
8. What is a quasar?
a) A star that emits gamma rays
b) A black hole that emits light
c) A galaxy with a very bright center, powered by a supermassive black hole
d) A planet with a highly elliptical orbit
9. What is a pulsar?
a) A star that emits radio waves at regular intervals
b) A black hole that emits gamma rays at regular intervals
c) A planet with a highly elliptical orbit
d) A galaxy with a highly elliptical shape
10. What is cosmic microwave background radiation?
a) The leftover radiation from the Big Bang, which fills the entire universe
b) Radiation emitted by galaxies
c) Radiation emitted by black holes
d) Radiation emitted by quasars
