Galaxies: immense star islands

Introducing galaxies: What is a galaxy?

Where did galaxies come from?

Looking at the Milky Way: How big is the Milky Way galaxy?

Where are the Milky Way's stars formed?

What kinds of nebula are in our galaxy?

What lies in the core of the Milky Way?

How big is the galactic halo?

Beyond the Milky Way: What is the local group?

Can galaxies collide?

What is an active galaxy?

How many galaxies are there?

Young astronomer: What galaxies can I see at night?