Have you ever looked up at the stars and wondered, "Why are they twinkling, and why are they different colors?" The answer is relatively simple, and easy to figure out. The stars themselves are not actually twinkling; the phenomenon is a result of atmospheric interference. The earth's surface radiates heat from the sun, not to mention the heat from the core, and as this heat rises above the earth, the stars seem to twinkle. This effect is similar to what happens during the summer time when you look across the pavement or a parking lot. The hot rising air causes images to waver or appear to be moving. The lower the star is in the sky, the more it will twinkle. But if this is to be the case, then why don't the planets twinkle too? Planets are larger sources of light as compared to stars, plus they are also closer than the stars we see, hence no twinkle. This is an easy method of determining which ones are stars, and which ones are planets. So the next time you're at a star party, see if you can pick out which ones are the planets and which ones are the stars.

Ok, so we've figured out why stars twinkle, but what about their color? A star can be identified by it's color, which is relative to it temperature. They are divided into what are known as spectral class. These classes are O, B, A, F, G, K, and M. Or better remembered as "O Be A Fine Girl, Kiss Me!" Stars that are classified as O type stars are the hottest and normally blue in color. The cooler stars are identified as M class stars and are red in color. Two examples of an O class star are in the constellation of Orion. The stars, Mintaka & Alnitak, the two opposite stars in Orion's belt are O class stars. Betelgeuse is a cool red supergiant, M class, easily seen during the winter nights at the top of the constellation. Beside their color, stars are also classified into different types. These types correspond to the temperature at it's surface against it brightness, allowing for its distance from earth. There are Brown Dwarfs, Red Dwarfs, Main Sequence stars, White Dwarfs, Red Giants, and Supergiants.

Brown Dwarfs are the beginning of actual stars. They are balls of gas that never reach critical mass, or Nuclear fusion. These stars, as they are called, are only 1/10 that of the Sun and will only burn briefly until they exhaust their energy.

Red Dwarfs are a step above Brown Dwarfs. These stars are smaller than our Sun, burning tens of billions of years. However, these stars are very faint, so we can only see the one's closest to earth. An example of a Red Dwarf would be Barnard's star.

Main Sequence stars have stared nuclear fusion and continue to burn for thousands, to billions of years. Our own Sun is a Main Sequence star. Large, massive stars will have a short main sequence stage, while less massive stars will remain in the main sequence much longer, burning for ten times longer.

White Dwarfs are stars that are about the size of the Earth, but whose nuclear fires have gone out. Nuclear fusion no longer takes place. The star, Sirius B, located next to Sirius, is a White Dwarf.

Red Giant stars have the same surface temperature as Red Dwarfs, but much larger and brighter which are reddish or orange in color. Red Giants are in the latter phase of development in a star's life, sometimes reaching 100 times their original size. An example of a Red Giant would be Aldebaran.

Lastly, very large stars will form what are called Supergiants. Two examples of Supergiants are again in Orion. Betelgeuse, in the shoulder of Orion is a Red Super Giant, and Rigel, in the foot of Orion, is considered a Blue Super Giant.

Hopefully this information will help the next time you go out into the night and gaze the wondrous sites called Stars.