Which proportion of the universe's galaxies can be seen from Earth.
a. nearly half
b. approximately 25 percent
c. far less than 1 percent
d. approximately 10 percent
c. far less than 1 percent
Why are most stars not destroyed by galaxy collision?
a. galaxies move too slowly for that kind of damage
b. galaxies don't have stars
c. gravity keeps them away from each other
d. galaxies are mostly empty space
c. gravity keeps them away from each other
Which of the following is an accurate description of cosmic microwave background (CMB) radiation? Select all that apply.
a. CMB increases across the universe
b. CMB produces differing temperatures across the universe
c. CMB is remnant radiation from the Big Bang
d. CMB is constantly generated by stars
b. CMB produces differing temperatures across the universe
c. CMB is remnant radiation from the Big Bang
Which was used to create the first image of a black hole?
a. visible light from the black hole
b. x-rays from inside the black hole
c. radio waves from matter at the edge of the black hole
d. ultraviolet light from objects in the black hole
c. radio waves from matter at the edge of the black hole
what do supernova remnant and planetary nebulae have in common? Select three correct answers.
a. They have planets circling them
b. They are composed of matter from dying stars
c. They contribute to interstellar space
d. They emit non-visible radiation
e. They are composed of only hydrogen and helium
f. They are diffuse
b. They are composed of matter from dying stars
c. They contribute to interstellar space
f. They are diffuse
The universe's galaxies have evolved since what point in time?
a. 23.4 billion years ago, when the universe first formed
b. 800 million years ago, when gas concentrations were optimal for galaxy formation
c. 13.8 billion years ago, right after the universe first formed
d. approximately 50 million years ago, after initial clumps of material were formed