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An independent monthly newspaper serving the community since 1988
  Night Sky
 

Enjoy the starry night skies
Be a considerate neighbor. Reduce nighttime glare.
Shield your outside lights downward.
Let the stars light up the night.

January 2016 night sky

—Charlie Christmann

Our lost sky:

It is something you expect in the city, but not in the rural areas. Over the last 25 years, bright yard lights and exterior floodlights have become very common. If you live in rural areas, just look toward Albuquerque or Rio Rancho, the orange light dome blots out any stars that reside there. As more and more people escape the city for the quiet of the country, they bring along with them their conditioned need to light up the night. With each new porch light or yard light, stars disappear from our view.

Even here in Placitas, the Milky Way is difficult to see on a moonless night—just a faint smudge in the sky. This was the place to come to see comets floating through the night sky, like Comet Catalina now visible from New Mexico. Back in Galileo’s time, the Milky Way was so bright that it cast faint shadows on the ground. What changed? The stars have not become dimmer over the last several hundred years, our sky has become polluted with artificial light scattering off atmospheric dust and pollution. The backscattered light obscures all but the brightest stars in our cities. In the surrounding suburbs, a few more might shine through. As an example, from central New York or Las Vegas, only the moon and bright planets are bright enough to overpower the nighttime sky glow.

In 2001, E. Bortle, a retired Westchester County fire chief and a monthly columnist for Sky & Telescope, created the Bortle Dark-Sky Scale. It ranges from 1 (no light pollution at all) to 9 (middle of New York City). A Class 1 sky does not exist here in America, the best we can do is a Class 2. If we had a Class 1 sky, the Milky Way would show its fine details and colors. Stars as dim as eighth magnitude can be seen. The Scorpio and Sagittarius region would casts obvious shadows on the ground. There would be a distinct bluish airglow near the horizon. The Zodiacal light would have an obvious color and stretches across the entire sky.

By Class 3, the Milky Way loses its fine structure; its dark voids and bright patches remain as does the outline of our home galaxy as it wanders across the sky. Only stars brighter than seventh magnitude would be visible. The Zodical light is striking in Spring and Autumn, but lost the rest of the year. Class 5 skies wash out the Milky Way overhead and obscure it on the horizon. We see only hints of the Zodical light in spring and fall. Light pollution domes are bright and ground objects are partly lit. Stars dimmer than 6th magnitude are lost.

In Class 7 suburban skies, we lose sight of the Milky Way all together. Dimmer constellations are less recognizable with many missing stars to outline their shapes. The sky takes on a yellowish or grayish glow and illuminates the underside of the clouds. The planets get harder to find. Fifth magnitude stars get difficult to find. In cities, Class 9 skies leave anything less than 4th magnitude invisible. Only the brightest stars in constellations are viewable. Clouds shine brightly in the sky and the sky glow is bright even overhead.

Albuquerque and Rio Rancho would have a Class 8 sky, obscuring stars less than magnitude 4.5 and hiding the Milky Way and all of the star clusters except perhaps the Pleiades. Western Placitas might make a class 7 sky while the eastern parts might be lucky enough to be Class 4.

You can help preserve what is left of our night sky by properly shielding exterior lighting, or better yet, turn them off when not needed for activities. For more information on protecting the night sky or finding ways to reduce the effects of your outdoor lighting, go to the International Dark Skies Association (darksky.org) and get involved. We have lost so much in the past 15 years I have lived in Placitas. Let’s do what we can to reverse the trend.

Morning comet:

Comet C/2013 US10 (Catalina) was predicted to be a naked eye object, but as it rounded the sun on November 15th between the orbits of Venus and Earth, it refused to get brighter than a 7th magnitude. When it was first discovered on Halloween day, 2013, it was thought to be an asteroid, hence the US10 designation. Additional observations refined the orbit showing it was steeply inclined to the plane of the planets and on a hyperbolic orbit. It is likely this is its first and last trip to the inner solar system.

The first week of January, get your binoculars out before dawn. Find the bright star Arcturus and look just above the star for a fuzzy green blob. For those with telescopes, you might be able to make out the comet’s twin tail. Since this comet is a visitor from the Oort cloud, it is traveling from south to north at about 103,000 miles per hour relative to the sun and will rapidly climb higher in the sky, making it viewable earlier in the morning.

Close conjunction:

It will be worth being awake a few hours before sunrise on January 8th. Not only can you look for Catalina, but you will be treated to a Venus-Saturn spectacle. The planets will rise at 4:33 a.m. and 8:37 a.m. less than one degree apart. Venus will be the brighter planet at a magnitude of -4.4. Saturn will be dimmer at a magnitude of 1.2. The constellation of Ophiuchus will be in the background and the moon will be a non-factor. Their closest approach occurs at 9:12 p.m. on the 8th, after they have set for the evening.

 
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