Galaxies and the universe

What is a galaxy?

What are galaxies made of?

Which galaxy are we in?

What is the shape of the Milky Way?

How big is the Milky Way?

Where is the solar system in the Milky Way?

How did the solar system form in the Milky Way?

What other galaxies are near the Milky Way?

How does the Milky Way travel through space?

What is special about the Milky Way?

How do galaxies form?

What types of galaxies are there?

Can galaxies run into each other?

What is the universe?

How old is the universe?

How big is the universe?

Is the universe changing?

How do galaxies move as space expands?

What was the big bang?

Is the universe expanding faster than it used to?

How have we learned so much about the universe?

How do astronomers study the universe?

What is dark matter?

What are black holes?

What are pulsars?

What are star clusters?

Could life exist elsewhere in the universe?

How will the universe end?