Compare the stars found in the galactic disk (where the sun is located), also known as Population I stars, with the stars in the halo of our galaxy, known as Population II stars.
Milky Way - Compare the solar system with the Milky Way Galaxy. (They are very different, but the terms are often confused.) What are two similarities and two differences in their structure?
What types of objects emit X-rays? - What types of objects emit X-rays? Why do they emit X-rays and not other wavelengths? Why do other objects not emit X-rays?