Measuring the distance to galaxies can be tricky. If a galaxy is fairly close, then we can look for a type of variable star known as a Cepheid variable. These stars vary in brightness proportional to its absolute magnitude. Since we can calculate the absolute magnitude of a Cepheid variable, we can observe its apparent brightness and calculate its distance …
Ring Around the Rosie
The rings of Saturn are perhaps the the most famous ring system in our solar system. Pictures of the rings are all over the web, most recently the composite image from Cassini. But what we think of as Saturn’s rings is only part of the story, because what we’re familiar with are the rings as seen in visible light. There’s …