Heavenly illusions in the Butler sky
What you see in the Butler sky is not always reality. There are many illusions up there.
Whenever you gaze upon the starry sky, you do not see the stars in real-time. You’re actually staring into the past in varying degrees.
Everyone knows that the stars we see at night are far away. Trying to express those distances in miles involves using values in the trillions, and except for the national debt, most of us don’t use trillions all that much.
It’s hard to get your mind wrapped around the concept of a trillion of anything. We’re talking a thousand billion here!
It’s easier to express stellar distance in light years. A light-year is the distance a beam of light travels in one year, moving at the speed of light just over 186,000 miles a second. If you do the calculations, that works out to about six trillion miles for just one light-year.
On average, most of the stars you see in the heavens with just your naked eye are anywhere from around 10 light-years to about 3,000 light-years distant!
Alkaid, the star at the end of the handle of the Big Dipper, is 101 light-years away, or about 606 trillion miles. Because it’s 101 light-years away, it’s taken the light from Alkaid 101 years just to reach our eyes. When you gaze at Alkaid, you’re not seeing it as it is right now, but as it was in 1921 when about 20 percent of American homes had bathtubs!
We can easily spot a much more distant star in the night sky right now. It’s Deneb, the bright star marking the tail of the constellation Cygnus the Swan, flying high in the evening southwestern heavens. Deneb is about 1,500 light-years away, so we see Deneb as it was around 500 AD, long before there even was a United States of America.
As far away as Deneb is, there are many other stars even farther away, many of which we can also see with the naked eye.
The question I get asked a lot is whether some of the stars you see in the night sky may not be around anymore. Are we just seeing the light from a star that’s met its maker? Have they already blown up in a colossal supernova explosion, as in the case of supermassive stars, or have they shrunk into white dwarfs like our sun?
Rest assured that 99.9999 percent of the stars you can see with your eyes or a small telescope are still alive and kicking. The lifetime of a fully functioning star at the very minimum is 2 billion years, and there’s no way, no matter how many carrots you eat, that you’ll see a star with your naked eye that is two billion light-years away. All those shiners in the celestial dome are still there.
Another major illusion in the sky is that the stars you see are single stars sitting alone in space. Most of them are actually star systems. Some are binary stars, where two stars revolve around each other.
Some may be triple, quadruplet, quintuplet or even more multiple star systems, with all of the member stars orbiting around each other in sometimes very complicated cosmic dances. Our sun is all by itself — the exception rather than the rule.
There are also double stars in the sky that aren’t members of the same stellar family but instead are stars that just happen to be in the same line of sight from Earth. They’re called optical doubles, and a great example is in the handle of the Big Dipper. The middle star of the handle that you see right away is Mizar, but if you look just above and slightly to the left of Mizar, you’ll see a dimmer star called Alcor.
Mizar is about 78 light-years away, and Alcor is slightly over 81 light-years away. Physically they have nothing to do with each other.
Another great double star, probably the prettiest in the sky, is Albireo. It marks the head of Cygnus the Swan, also known as the foot of the famous “Northern Cross” within Cygnus.
To the naked eye, Albireo looks like an unassuming single star, but with even a small telescope you can see two stars, one with a distinct bluish hue and the other sporting an orange glow. They’re a gorgeous duo of stars, about 400 light-years from our backyards.
It’s not known if they’re orbiting each other in a binary system, but if they are, their orbit around each other would take about 100,000 years. Don’t wait up for that.
Celestial Happening this week: On Monday night, Nov. 28, the new crescent moon passes just below the moderately bright planet Saturn in the south-southwestern sky. On Thursday evening, look for the first quarter moon just below the much brighter planet Jupiter in the southeast heavens.
Mike Lynch is an amateur astronomer and retired broadcast meteorologist for WCCO Radio in Minneapolis/St. Paul. He is the author of "Stars: a Month by Month Tour of the Constellations," published by Adventure Publications and available at bookstores and adventurepublications.net. Contact him at email@example.com.