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January 28, 2011

How to see the Milky Way

This looks exactly like the place where I regularly put in my kayak.  It's a still winter night, the mouth of the river is off to the right leading into a larger body of water.  The glow of a nearby town only slightly illuminating the horizon behind the evergreens.  No other lights around which creates a night free of light pollution.  And the Milky Way looms above like a massive space creature. 

The winter sky is filled with bright stars.  In fact, seven of the twelve brightest stars visible from Earth (not counting the Sun) shine in winter.  It is one of the best times to star-gaze. 

This band on the sky is the profile of our spiral galaxy seen edge-on from inside it. 

It's a picture by Dan Stodola, and it could be a picture of where I live.  But, sadly, it's not.  I have never seen the Milky Way from my home.  There is just too much light pollution. 

Perhaps two-thirds of the world's population can no longer look upward at night and see this amazing sight.

The Milky Way is dimming as a result of light pollution: the inadvertent illumination of the atmosphere from street lights, outdoor advertising, homes, schools, airports and other sources.  Every night billions of bulbs send their energy skyward where microscopic bits of matter - air molecules, airborne dust, and water vapor droplets - reflect much of the wasted light back to Earth.  Currently, the only way to view the Milky Way with the naked eye is to be about 100 miles from the nearest metropolitan area, or to be around low light pollution. 

Comparison showing the effects of light pollution on viewing the sky at night. The southern sky featring Sagittarius and Scorpius. Top image shows the sky from Leamington, Utah (population 217). Bottom image shows Orem, Utah (a metropolitan area with a population of around 400,000).

There are three types of light pollution:
  1. Sky Glow - The orange glow seen over towns caused by upwardly directed or reflected light. 
  2. Light Trespass - Any light shining where it is not needed.
  3. Dazzle - Excessively bright and misdirected light.
All three can be eradicated using capped lights that do not shine upwards into the sky.  We need lighting to guide us after dark and for safety, but we do not need light that shines upwards into night skies. 

In recent years engineers have developed more efficient bulbs with "sky friendly" fixtures that can preserve dark skies and decrease energy costs.  Here's an example of "good" vs "bad":

GOOD - Post-top ornamental fixtures can minimize light pollution via a lamp reflector located above the bulb. 

BAD - Non-cutoff fixtures like this "acorn" ornamental lamp causes light pollution.

GOOD - Flat-lens cobra head fixtures provide excellent roadway lighting with greatly reduced glare and no uplight. 

BAD - The ubiquitious drop-lens cobra head luminaire produces a level of glare and uplight that is both unacceptable and unnecessary. 

I can still see Orion from home because it's one of the brightest constellations.  But even brilliant Orion will eventually fade if poorly-designed lights proliferate. 

It's a big loss, too.  Young sky watchers (like myself years ago) grow up to be scientists, explorers, poets, philosophers, and school teachers.  But kids aren't likely to watch or be inspired by... a blank sky. 

The point of raising awareness of light pollution is that it touches many areas of people's lives, from simply not being able to see the natural heritage of a starry night sky to affecting the habits of animals, energy consumption, economic resources, and astronomical research. 

This image of Earth's city lights was created with data from the Defense Meteorological Satellite Program (DMSP) Operationsl Linescan System (OLS).  Originally designed to view clouds by moonlight, the OLS is also used to map the locations of permanent lights on the Earth's surface.  If you're like me, you can easily pin-point where you live and notice that it's surrounded by bright lights.

The Milky Way's visibility, or lack of it, is the easiest measure of your sky's light pollution - the glow from all the poorly designed and improperly aimed outdoor light fixtures for dozens of miles around.  If they illuminated only the ground as their installers intended, rather than wasting some of their light uselessly sideways and upward, we could not only save many megawatts of electricity, but the world's view of the starry universe would be vastly improved.

The best way to avoid light pollution is to turn off exterior lights.  However, there are times at which you'll need some lighting outside at night.  Turning on the flood lights when you leave for a night out so you'll be able to see your way to the door when you come home is not only a waste of energy, but doing so can be an annoyance to your neighbors as your lights fill the night sky and their lawn with unwanted bright light. 

Motion Detector Lights

Avoid this problem by insatlling motion detector lights on the exterior of your home.  You can still turn on the ligts when you leave for the evening, but they will only come on when the motion detector picks up movement in the driveway or around the house.  When your car pulls into the driveway, for example, the lights will come on long enough for you to get inside.  In additon, these lights are a good security measure to deter intruders.  Just make sure you get the ones that face downward and not out. 

Landscape Lighting

Landscape lighting is subtle and adds to the beauty of the walkways around your home.  These inexpensive lights are also likely to be energy efficient.  Many of these types are solar powered, storing energy from the day's sunlight to power them. 

Dome-covered Lights

If your home's exterior must have several lights that stay on for extended periods in the evening, investing in domed fixtures to cut down on the light pollution is a good idea.  Since light rays go out in every direction from the source, blocking their path with a dome on top of the bulbs will prevent much of the light from shining into the sky.  The domes may actually intensify these lights (especially if they are mirrored inside) and cause ground lighting to be brighter (which allows you to use a lower wattage bulb, therefore less energy used), but the sky will be much darker having them in place. 

If we could all be responsible with our use of exterior lights - from our homes and businesses to the street lights from the Department of Transportation - anyone in the world be able to just step outside at night and be greeted with the glorious vision of our Milky Way.

The fact that it also saves energy is a win/win situation. 


  1. Lovely pictures, I must make more effort to learn more about the night sky - I can only find the north star and I'd like to be able to identify the constellations.

  2. The picture of the lights in the night sky around the world is depressing. Thanks for all the useful info though.


  3. It is depressing, but not hopeless. Just driving a block or 2 from home I see a crazy amount of wasted light - and I don't live in a big city! The fight to minimize uplight can still be won though. Spread the word, and thank you for supporting. :)

  4. Thank you for you comment. You can learn more about our night sky. There are several web sites out there to let you know what's going on in the sky, and when. I like: http://www.skyandtelescope.com/observing/ataglance
    So visit a state park (or some large area away from lights) on a clear, moonless night and stargaze away.

  5. Thank you for visiting my blog.

    Also, I love this information. Very informative and just so many interesting and very cool facts. Love it. I love sitting outside and just looking at the stars in peace.

  6. Thank you Kristin. I love to stargaze, too... very much in fact. And we're not the only ones. That's why it's so important to not only keep the stars visible, but to also bring back the visibility of those that are being hidden by our lights.

  7. This is incredible, it's wonderful that there is so much around us that we've barely even discovered yet! I would love to see the milky way so this is a great starting point.



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