All the Colors of the Rainbow

The Sun, our own star, is yellow. A prism shows that its light really contains every color, but the dominant color is yellow. However, all but the brightest stars in the night sky appear to be white. This is because the Sun is so close to us, and brilliant. The other stars are so far away - some millions of times further away that they appear dim.

Our eyes are not very sensitive to color. Dim objects, no matter what their color, appear white. If our Sun were as far away as the other stars, we could barely see it, and when we did, it would appear white.

We can see the true, "dominant," colors of some of the brightest stars. Arcturus (follow the arc of the handle of the Big Dipper to Arcturus) is yellow, like the Sun. Antares, now near the southern horizon, is red. Vega, almost directly overhead, gleams a brilliant blue-white. Aldebaran, the eye of Taurus the bull, is orange.

Through binoculars, we can see the color of other stars. The North Star, Polaris, is yellow. Albireo, at the foot of Cygnus, the Northern Cross, is a double star, topaz and blue. Almach, the left foot of Andromeda, is also a double star, orange and emerald.

If we could see the colors of all the stars, the sky would be a scattering of multi-colored gems gleaming on a velvet background.

Like an iron bar heated in a fire. the color of a star tells us how hot it is. At first, the bar glows a deep red, like Antares. As it gets hotter, it becomes orange, like Aldebaran, then yellow, like our sun. As the bar gets hotter and hotter, its color moves through the entire spectrum of the rainbow. A star a little brighter than the Sun would appear greenish. The hottest stars, like Vega, are blue-white.

The energy produced by a nuclear fire in the core of a star is the same as that of the heat it radiates to space. Its temperature and color remain the same. The Sun is in its prime, and its friendly yellow glow will continue for another five billion years. Only when a star is dying, as are Antares and Aldebaran, does it grow and change color.

(08/29/07)