 It's human nature for us to desire a system by which we can identify things. We always want to take the disorder of nature and put it into a nice, orderly, friendly-looking chart. And stars are no exception to that. This is your space pod for September 18, 2015. Stars in our sky may all look the same, but when we look at them in great detail, we actually find out that they lead completely different lives from each other. Now for the sake of simplicity, we're only going to be looking at generic stars. We won't be looking at exotic objects like neutron stars. That's for a later space pod. There's two classifiers we'll be talking about in this pod. The Harvard System and the Morgan Keenan Keller Classification System. The Harvard System is the one that most people are familiar with. It's a fairly simple system based on the surface temperatures of stars. There are seven classes that a star can be a part of, and they use letters as their designators, O, B, A, F, G, K, and M. There's been a few letters added on since for special objects, but once again, we'll be saving that for a later space pod. O stars have the hottest surface temperatures. M stars the lowest surface temperatures. From lowest to highest surface temperatures, the letters go M, K, G, F, A, B, O. You'll notice that the hotter stars are blue and the cooler stars are red, opposite of what you may find in your water taps. Each individual letter is then subdivided into numerals, with zero being the hottest surface temperature of that letter designation, and nine being the coolest. Using this scale, our sun is a G2 star. The Morgan Keenan Keller Classification System has more to do with spectral lines. Dark lines in the light spectra from a star, caused by elements absorbing those specific wavelengths of light, and also the specific surface gravity of a star, which also affects the total amount of light output of a star in what we scientists like to call luminosity. This system uses Roman numerals to describe the overall character of a star, or what's designated as a luminosity class. There are a plethora of classes, so let's keep it simple by taking a look at the three most commonly used. One for supergiant stars, three for giant stars, and five for main sequence stars. When both the Harvard and Morgan Keenan Keller classification systems are combined, we get a clear and concise understanding of the stellar object that we're looking at. Our sun in the combination of these two systems is now a G25 star. G2 being its surface temperature, and five, meaning it's a main sequence star. Thanks for watching this Space Pod. I'm Jared Head. Don't forget to like, comment, and subscribe to us on social media. And we can't do these Space Pods without the amazing support of our Patreon patrons. And you can be one too, to help us continue to make these awesome Space Pods. So, until the next one, keep exploring.