Brightness of Stars
Star Colors
Stars are grouped together by what astronomers call spectral classification. This groups the star by it's color, composition, and size. For example, an O type star has a color of blue and it's temperature is 70,000 degrees Fahrenheit. A B type star is blue-white and is about 33,700 degrees Fahrenheit. An A type star is white and is about 15,000 degrees Fahrenheit. A F type star is also white but it is about 12,000 degrees Fahrenheit. A G star is yellow and is about 9,400 degrees Fahrenheit (the sun is a G star). A K type star is orange and is about 7,200 degrees Fahrenheit. Finally, a M type star is red and is 4,900 degrees Fahrenheit. As you see, the duller the color of the star is, the cooler it is.
Stars are mainly huge balls of gas held together by gravity that give off light and heat. But there are also many different kinds of stars. Stars have different colors, sizes, and temperatures.
Stars are all made of the same materials. But stars come in many different sizes and have different brightnesses. When we observe them at night from Earth, they all look as if they are all the same distance away from us, but truly, all the stars are from different distances away. If we just look at the star from Earth, we can't tell how bright a star is. Astronomers invented two different systems to tell how bright a star is. The apparent magnitude scale tells how bright a star is as it appears on Earth, and the absolute magnitude scale tells how bright the star really is. Magnitude is the term astronomers use to measure the brightness of a star.
Of course, when you first look at a star, it seems that they are all the same color. But while observing the stars carefully, you can see a little color, such as a blue and orange.