As the lights go down during Earth Hour on Saturday , March 31 around the world, take advantage of the darkness and look up at the stars. Light pollution not only wastes energy, disrupts circadian rhythms of wildlife but also diminishes the beauty of the night sky. To see how much light pollution affects stargazing in your neck of the woods here’s a little test you can conduct from anywhere – be it your driveway, sidewalk or local park – that backyard astronomers do to gauge sky conditions.
To do this sky test – you need to track down the Little Dipper and see how many stars you can find of this stellar pattern. It won’t stand out like its neighbor, the Big Dipper, and it is actually trickier to see all its stars – which is precisely why it makes it a great gauge for light pollution.
To start your experiment, face the northeast horizon and look halfway up the sky for the bigger and bright neigboring star pattern called the Big Dipper.
During mid evenings this time of the year you should be able to see the Big Dipper lying upside down or on its side with the handle pointing down towards the horizon.
Take the two end stars in the bowl and draw an imaginary line down and left until you hit the next brightest star – which is the North Star or Polaris. It marks the tail end of the Little Dipper or little bear. Now for the tricky part – try and connect the dots and trace out the remaining stars of the Little Dipper pattern.
Can you see all the stars that make up the handle and bowl? Backyard astronomers use these stars to get a sense of how light polluted their local skies. The darker the skies, the fainter the celestial objects you can see.
While the two end stars of the little bowl are considered magnitude 2 and 3 on the brightness scale astronomers use - making them just visible from suburban skies – the remaining two stars in the bowl and handle are all 4th magnitude – which means they are usually not easily visible under lots of light pollution in urban and suburban sites.
To really tell what difference light pollution can make – try your hand at looking for the Little Dipper stars before all lights are turned off for Earth Hour and then during the event. Since you may find not all your local city lights may be turned down – the effect may be minimal. So to really appreciate the effect all those artificial lights have on the night sky – try doing these same observations on any clear night – first from the city and then again from a dark countryside location. You will be amazed at the difference.
For a comprehensive rundown on what you can do to conserve the night sky and how to reduce light pollution check out the International Dark Sky Association website.
Andrew Fazekas, aka The Night Sky Guy, is a science writer, broadcaster, and lecturer who loves to share his passion for the wonders of the universe through all media. He is a regular contributor to National Geographic News and is the national cosmic correspondent for Canada’s Weather Network TV channel, space columnist for CBC Radio network, and a consultant for the Canadian Space Agency. As a member of the Royal Astronomical Society of Canada, Andrew has been observing the heave