Page 26 - BBC Sky at Night Beginners Guide to Astronomy - 2017 UK

LIGHT

POLLUTION

THE INTRUSIVE EFFECTS OF LIGHT POLLUTION
ARE EVERY ASTRONOMER’S BUGBEAR. WE LOOK
AT THE CAUSES AND EFFECTS OF THIS IRRITANT

One of the biggest problems facing astronomers today is light The biggest casualty is the band of the Milky Way, the band of
pollution. It’s caused by the vast array of street lighting and light from stars that stretches high across the autumn skies. It has a brightness
LARRY LANDOLFI/SCIENCE PHOTO LIBRARY, STEVE MARSH X 3, DARK SKIES MAP: PAUL WOOTTON buildings, which scatters light off particles in the atmosphere. In the
of around mag +4.5. This makes it accessible from darker suburban
worst cases, this causes the night to take on an unearthly orange glow. locations, but washed away if you’re in a place with more lighting
From some places the effect of light pollution can be to virtually wash around. As more people now live in towns and cities, an increasing
away any evidence that there is a wondrous vista lurking behind it. number of people have never seen the Milky Way.
Add in a dollop of hazy weather and your viewing gets even worse, as
the light gets bounced around even more. COUNTRY WISE
Not surprisingly, the worst places for light pollution are the Other objects that suffer include those that appear as fuzzy patches
major towns and cities. However, stargazers who live in more rural in the sky, namely nebulae, star clusters and galaxies. So if you live
locations can be just as bothered by the annoying bright light from a in the countryside, you’re probably able to see such deep-sky wonders
neighbour’s badly-adjusted single security light. One light can be just as the Orion Nebula, the Sword Handle double cluster in Perseus and
as terrible as an entire city when it comes to observing. Wherever you the Andromeda Galaxy – but if you live in a city, you are limited to
are, the problem is getting worse as towns spread and people feel they viewing the brightest stars and the planets.
need more protection for their homes. Needless to say, if you are hampered by light pollution, then you
With increasing light pollution, the grandeur of the night sky has can always place your telescope carefully in the car and drive off to
gradually been eroded. As light pollution increases, the number a dark site. Maybe you’d like to try one of the fi ve dark sky sites that
of stars you can see decreases. This is all described by limiting we’ve identifi ed in the UK on the map to the left? One of them is the
magnitude – ie, what is the faintest star visible? In very dark locations Galloway Forest Park, which in 2009 was designated as the UK’s fi rst
the eye can see stars just below mag +6.0 (the higher the number, the Dark Sky Park.
fainter the star), but with more lights around, this can be reduced to a And if you’re confi ned to your garden? Never fear – just take a look
handful of only the brightest fi rst magnitude stars. at our four tips that should help lessen the effects of light pollution.
26 skyatnightmagazine.com 2012