England's 'Cosmic Census' Reveals Scale of Light Pollution

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England's star census aims to promote dark skies and engage people in the fight against light pollution. (Photo: Dualiti Photos/Flickr)

In an effort to discover and preserve vestiges of the English night sky unspoiled by light pollution, the British Astronomical Society joined forces in February with The Campaign to Protect Rural England (CPRE) to launch the great Star Count of 2019. Now they have some results.

"A dark sky filled with stars is one of the most magical sights our countryside has to offer," Emma Marrington, dark skies campaigner at CPRE, told The Guardian during the census. "Increasingly, however, too many people are denied the opportunity to experience this truly natural wonder."

A nighttime view of the United Kingdom as captured by NASA and NOAA's Suomi NPP satellite. (Photo: NASA)

For most of February, they groups asked British residents to look for the constellation Orion with its four corners and famous three-star belt. The goal of that effort was to create a more accurate map of the best places to enjoy the night sky and to make progress in combatting light pollution in other areas.

In this long exposure, light pollution from St. Ives casts a orange haze in the night sky above the mysterious Men-an-Tol, one of the best known megalithic structures in Britain. (Photo: Matt Cardy/Getty Images)

Now that the most recent count is complete, it's clear there's still work to do.

Just 2% of people of the 2,300 participants were able to enjoy a true dark sky, according to the CPRE site, which offered details:

Well over half of all participants (57%) failed to see more than ten stars, meaning that they are severely impacted by light pollution. In contrast, only 9% of people experienced ‘dark skies’, counting between 21 and 30 stars, and just 2% experienced 'truly dark skies' and were able to count more than 30 stars – half the proportion of people able to do so during the previous Star Count, in 2014.
Astronomers are using the census to help locate and preserve England's last remaining pockets of dark skies. (Photo: herdiephoto/Flickr)

Because the three stars in Orion's belt — Alnilam, Mintaka and Alnitak — glow fairly bright, they're generally an excellent starting point for a star count campaign, even under some of the worst light pollution conditions. It's when you start recording the stars within its four corners that the impact of light pollution begins to skew results wildly from region to region.

As shown in the time lapse below of various levels of light pollution in the U.S., Orion looks a lot different under the lights of San Francisco than it does under the perfectly dark conditions of Goblin Valley State Park, Utah.

In a 2015 study aptly called Night Blight, the CPRE used nighttime satellite imagery to conclude that only 22 percent of England experiences night skies completely untouched by light pollution. This number pales in comparison to Wales (57 percent) and Scotland (77 percent), which benefit from significantly lower levels of population. Not surprisingly, 19 of the brightest 20 districts are London boroughs, while nearly all the darkest counties skirt the edges of England's borders.

Mars and the milky way over the south coast of the Isle of Wight. (Photo: Brian Tomlinson/Flickr)

So how do communities get the night back? Some of the easiest fixes, according to dark sky proponents, come from adding shielded light fixtures, motion sensors and programmable LEDs. Through activities like this national star count, the group is hopeful that people will simply take the time to look up and appreciate the increasingly fleeting beauty of their heads.

"You don’t have to be an astronomer to be influenced by a view of a starry night," Christopher Luginbuhl of the Flagstaff Dark Skies Coalition told Sky and Telescope. "And you don’t have to know how far a star is to get the basic message that the universe over your head has meaning and perspective to give to human life."