Cosmo 101 Cepheid Variables

Hey bloggers! We’ve now made the transition to cosmology! And I have a test on General relativity tomorrow oh no! Anyway we’ve already gone over a lot of the stuff that we are talking about in class but I noticed that while I talked about Hubbles law and all (you can read about it here), I didn’t mention Cepheid variable stars. These stars a very interesting in that they blink. Their luminosity literally varies periodically like a lighthouse. But the cool thing is that there is a very linear relationship between it’s period (how fast it’s gets light and then light again) and it’s luminosity (how bright it is). I’ve included a graph to show this relationship. The cool part is the since we know this, if we look out into the sky and see a variable star we can tell how far away it is. How? Well we can see measure it’s period and see how bright it comes across to us. If we know (from the graph) how bright it’s really suppose to be we can calculate how far it. Yay! You may have heard of these stars before but usually they are referred to as standerd candles.