Sirius, the brightest star, is 8.8 light-years from earth. that means
a) sirius is not part of the milky way.
b) sirius is closer to earth than the sun.
c) we see sirius as it looked 8.8 years ago.
d) it would take us 8.8 years to reach sirius.

Nebulae are enormous clouds in outer space. they are made mostly of hydrogen gas, helium gas, and dust. some nebulae glow brightly, while others do not. the stars that people see are huge, bright balls of glowing gas. they are made mostly of hydrogen and helium. which statement correctly describes other ways in which nebulae and stars are different? a. stars can form inside a nebula but a nebula can never be produced by any star. b. a star always has a higher density than a nebula. c. stars can never form inside a nebula but a nebula can be produced by any star. d. a nebula always has a higher density than a star.