Why are stars different colors?

Throughout history mankind has gazed up at the stars in awe and wonder. To the naked eye, most of the stars appear white. As the light from the stars comes through the earth’s atmosphere, they appear to be twinkling. Until about two hundred years ago, everyone that studied the stars thought that all stars were white. The astounding part is, stars come in almost all of the shades of the rainbow.

When scientists started learning more about light and light waves, they realized that there are various kinds of light and the wavelengths can be wide or tightly packed. As they studied the planets they began to recognize that light can be perceived in different shades of color based on the wavelength, and that wavelength can change based on a star’s temperature.

Colored Stars

A type of science physics called ‘blackbody radiation’ was developed and they continued to examine the various temperatures and colors. It seems that the stars with ‘cooler’ temperatures have energy that is radiated in the red tones of the electromagnetic color spectrum, while those with ‘hotter’ temperatures had energy that is radiated in the blue and white tones of the electromagnetic color spectrum. This makes the cooler stars appear red and the stars with the higher temperatures appear blue or white. From cool to hot, the colors can appear red, orange, yellow, green and blue. If you remember the colors of the rainbow, you will see that these are in the same order.

There is another important factor that can alter a stars color. If the star has any elements in its atmosphere it can change the light wavelength and that will cause a change in the color that we measure or observe. This may explain why there are so many different colors in the stars that are being studied.

B-class stars in the Jewel Box cluster

The coolest stars are the red stars and their temperature is around 3,000 degrees C. Our own sun has a temperature of around 6,000 degrees C and glows orange/yellow. Green stars have a temperature of about 10,000 degrees C and the blue stars, which are the hottest, are about 25,000 degrees C.

The largest stars in the universe expend all of their energy much more quickly the smaller stars. This means that they have a very short lifespan. Our sun in considered to be a medium-sized star and it is half-way through its lifecycle. But it also has millions and millions of years left to shine brightly for us.

Ternary Color map

So, as you can see, the color of a star depends upon the temperature as well as any atmospheric contributions it may have to distort the measurable temperature. Scientists have developed very sensitive equipment that works with the telescopes to observe and note the rainbow colors of stars that we can see. This is the science of spectroanalysis and the scientists can detect not only the star’s color, but what the star is actually made up of. The elements of a star will help as we classify the solar systems and galaxies that we discover.

Star Colors and Temperatures

Why are the stars different colors?