Everyone loves to observe the beauty of the star-studded night sky, to say nothing of the dazzling images from the Hubble Space Telescope. But how many of us truly understand how stars shine, where Saturn's rings come from, or why galaxies have their distinctive shapes? Observational astronomy excels at imaging and cataloging celestial objects, but it takes a more rigorous discipline to come up with physical explanations for them. That field is astrophysics.Astrophysics uses the laws of physics to investigate everything beyond Earth.