Now That’s a Star of a Different Color!

BY DENNIS MAMMANA

Week of February 5-11, 2023

I’ve been gazing skyward for more than six decades, and in that time, I’ve learned a few things. One is that novice stargazers have some deeply ingrained misconceptions about the heavens.

For example, many think that we cannot see the moon during the daytime. Others believe that the Big Dipper is always visible in our sky. Still others think we see the stars as they appear now, rather than as they were centuries ago.

But one of the most common misconceptions is this: “If you’ve seen one star, you’ve seen ‘em all.” This is a pretty understandable perspective; after all, stars appear simply as points of light. How different could they possibly be?

Well, ask any experienced sky watcher and they’ll tell you that no two stars are exactly alike, but that each displays its unique personality in a number of ways. I like to say that stars are people too!

One of the most visible characteristics of a star is its color. Most stargazers don’t notice this immediately because the human eye is incapable of perceiving color well under low light conditions. We know this to be true if we’ve ever looked around a relatively dark room; shapes and shades of gray are pretty easy to spot but colors seem nonexistent. Turn the lights on, however, and we find that we’re surrounded by vibrant colors.

When gazing skyward we discover that star colors are quite subtle. Binoculars or telescopes capture much more light than the human eye and make these a bit more obvious. So, if we’d like to see star colors with the naked eye, we need to look toward the brightest of stars.

The best place to start your search is within the great constellation of Orion, the hunter. At this time of year, look for it midway up in the southeastern sky just after dark.

We can trace the stars in Orion’s large vertical rectangle of four bright stars to form the hunter’s shoulders and knees; at its center lie three stars that form a nearly straight line that represents the belt of the great hunter.

The bright star marking the northeastern corner (one shoulder) of Orion is known as Betelgeuse. This red supergiant star glows with an orange light that is pretty tough to miss. At the opposite corner (in one of the hunter’s knees) lies sparkling Rigel, another supergiant that displays a slightly bluish-white color.

Star colors are more than just a curiosity; they tell us something about stellar temperatures. While our sun glows with a surface temperature of around 10,000 degrees Fahrenheit, reddish-orange stars like Betelgeuse are relatively cool (6,300 F) and can often live much longer than the sun. Bluish-white stars like Rigel, on the other hand, are tremendously hot (18,000 F); they can burn this furiously for only a relatively short time and, therefore, must be much younger than the sun. After you’ve noticed these two fine examples of stellar color, check out some of the other bright stars around the sky to see what you can learn about their rel- ative temperatures and ages. Once you do this you, too, will realize that stars are people too!

Visit Dennis Mammana at dennismammana.com.