Types of Stars

There are seven main types of stars. In order of decreasing temperature, O, B, A, F, G, K, and M. This is known as the Morgan–Keenan (MK) system. The majority of all stars in our galaxy and even the Universe are main-sequence stars. All in all, there are many different types of stars, ranging from tiny brown dwarfs to red and blue supergiants. There are even more bizarre kinds of stars, like neutron stars and Wolf-Rayet stars. And as our exploration of the Universe continues, we continue to learn things about stars that force us to expand on the way we think of them. A Solar-type star has about the same mass as our sun and is fusing hydrogen into helium at its core. The result is the familiar yellowish glow that characterizes many of the stars we see in the sky, and a long-lived, stable star with a lifetime of billions of years.

Stars that are much less massive than our Sunburn cooler, and live longer – potentially for hundreds of billions of years. The resulting dull red stars are the most common type in our galaxy but since they’re quite dim, they’re hard to see. Stars that are much more massive than our Sunburn hotter but for much less time, living and dying within a few million years. Just as a hot gas flame burns blue, so these stars show a bright blue light and because they’re so bright, we can see a lot of them from the ground. The brightest Solar-type star in the sky is Alpha Centenary, which is very close to us. Alpha Cen is a double-star system we call a binary, but the brighter component is only a little larger than our own Sun.