Light pollution robs starry nights of sparkle

Constellations could fade from view in two decades as experts call for a global switch-off at night

A TWINKLING night sky can inspire wonder in even the most jaded.

But light pollution is slowly snuffing out the celestial spectacle, and by the time a child born today reaches adulthood, they will see fewer than half the stars currently visible, scientists predict. The problem, known as “skyglow” is far worse than previously thought, with the night sky brightening by 9.6 per cent on average globally each year.

“At this rate of change, a child born in a location where 250 stars were visible would be able to see only about 100 by the time they turned 18,” said Dr Christopher Kyba, at the German Research Centre for Geosciences, and lead author of a new paper on the phenomenon.

The Royal Astronomical Society (RAS) said the change could see some of the fainter constellations, such as Cancer, fading away, as well as distant astronomical features like the Orion nebula and Andromeda galaxy.

Later this month, the green comet E3ZFT will be vaguely visible shooting across the night sky, but a few decades from now it could be invisible.

Dr Robert Massey, deputy executive director of the RAS, said: “Some of the sights we have taken for granted, especially if they are challenging to see to begin with, may no longer be visible in the future.

“The green comet that is theoretically going to be visible later this month is a useful example of something that will be harder to see if things carry on as they are.

“The beehive cluster in the constellation Cancer is an example of something that is a sign of a good dark sky, so it seems obvious if skies brighten that could become more difficult to see.”

Previously, scientists measured light pollution using satellites, but they fail to accurately pick up what humans can see from the ground.

For example, blue light is particularly disruptive to night vision yet satellites that can image the whole Earth are not sensitive in the wavelength range of blue light.

For the research, more than 51,000 citizen scientists across the globe were asked to look at the night sky and report which star charts best matched their view. Each chart showed how the sky would look under different levels of light pollution.

The researchers, who published their work in the journal Science, said that a few simple rules, including shutting off advertising signs at night, and avoiding cold white lighting, could have a big effect on skyglow.