All Main-Sequence Stars Are Composed Primarily of ____ and ____

Q38: The major reason for differences in temperature

Q39: Jets of gas called _ shoot upward

Q40: Black holes are black because _.<br>A) dust

Q41: A concentration of older stars that shared

Q42: How far is a light-year?

Q44: The _ was the formation of helium

Q45: Astronomers believe that a _ must lie

Q46: What is a parsec?

Q47: The radiation emitted by stars, galaxies, and

Q48: What powers the Sun?