The splendor of the night sky continues to unfold, interrupted only by clouds and light we send upwards, competing with star light coming down. The magnitude of our street lights, parking lot lamps, back yard lights and neon signs dazzle our eyes but they are nothing compared to the light output of just one star.
The splendor of the night sky continues to unfold, interrupted only by clouds and light we send upwards, competing with star light coming down. The magnitude of our street lights, parking lot lamps, back yard lights and neon signs dazzle our eyes, but they are nothing compared to the light output of just one star.
After all, the sun is an average-sized star, and there are billions of stars in our galaxy alone, beaming their light our way. Any one of those stars is so bright you would not dare star at it if close enough, anymore than you should stare at the Sun and damage your eyes. It is the vast distance between us and the other stars that make them safe to see.
The same way, the only reason our puny man-made lights fog our sky with glare if not adequately shielded, is that we are so close to them and there are so many nearby.
In 1823 German astronomer Heinrich Willhelm Olbers described a baffling paradox. Known today by his name, the paradox asks why, given the possibly infinite number of stars in every direction throughout the Universe, does not the collective star light make our night sky dazzlingly bright?
There are various explanations offered why this isn’t the case. One is that the Universe is expanding, and the more distant the light source is, the more the frequency of that light is shifted towards the red, even beyond the limited spectrum of light our eyes can see. Light can be shifted into microwave wavelengths, and astronomers do detect what is known as the “cosmic microwave background radiation” detected by radio telescopes.
Anyway, we can be thankful for the way the Universe has been put together, for the beauty the night sky provides with stars seemingly like salt shaken from a salt shaker across the black void.
How are the stars from your backyard?
It may be surprising to know that even on the very best of nights, you won’t see millions of stars- except with a telescope. Available to the unaided eyes are only around 4,000 to 5,000 stars, and half of that is always below the horizon at any given time. Even still, from a remote location with transparent air, no Moon and no manmade lights, the sky seems to dazzle.
Even with annoying glow on the horizon from shopping malls and towns, you can enjoy the sky. Make the best of it; situate yourself so trees or structures block the glow. You are bound to see the most stars overhead (in the “zenith”).
Star brightness is measured on the magnitude scale. The faintest we normally can see with unaided eyes is about +6th magnitude. With some light pollution or haze you may only see down to +4 or +5, but that’s still a lot of stars.
The stars of the Big Dipper are mostly magnitude +2. Constantly facing the Little Dipper in the north, the Big Dipper is much easier to find. The Little Dipper contains the North Star (Polaris) at the end of it’s “handle”, which is also magnitude +2. Most of the Little Dipper’s stars, however, are fairly dim. If you can trace it, you know your sky is clear and relatively dark.
Communities and residents can both save energy and spare the night sky by using outdoor lights with good shields. These require less wattage and reflect the light to the ground where it is needed. An outdoor light should never glare in a person’s eyes, unless you are standing under it.
There is still a vast cosmos you can see the next clear night. Let’s do what we can to keep it.
For more information on protecting our night sky, visit the International Dark Sky Association at www.darksky.org.
New moon is on August 17.
Send notes to email@example.com. Please mention where you read this column.
Keep looking up!