How many stars can you see in Orion? The answer could be important.

A countryside charity is asking people across the UK to look up this February – and report what they see.

By Simon Ingram
Published 13 Feb 2020, 10:34 GMT, Updated 16 Dec 2020, 11:59 GMT
Happisburgh lighthouse in Norfolk, with the constellation of Orion directly above it. In the corners of ...
Happisburgh lighthouse in Norfolk, with the constellation of Orion directly above it. In the corners of the frame, the yellow glow of light pollution can be seen.
Photograph by Bill Allsopp, Alamy

It was reported late last year that the brightest star in Orion – Betelgeuse – has reached its dimmest in over a century. This has prompted astronomers to speculate whether it may be about to explode, in a supernova bright enough to be seen by day. But the other stars in this famous constellation are about to draw interested eyes for another reason: an attempt to gain insight into the health of the night sky.

CPRE, the countryside charity (formerly known as the Campaign to Protect Rural England) has launched its 2020 Star Count – a public-powered initiative designed, the charity claims, 'to reconnect people across the country with the wonder of a truly dark sky.’ The method requires a few steps outside, and a clear night to do so between the dates of 21-28 February. Once these are achieved, find Orion and count the stars you can see, then submit your findings on CPRE's website

“We chose the Orion constellation for our Star Count as it is one of the most well known in the winter sky,” says Emma Marrington of CPRE. “His famous belt of three bright stars in a row can be easy to find if you’re looking up, and facing south after dark.” 

Using the week of February with a new moon to minimise natural light interference, once the constellation is identified, CPRE is asking observers to count – with the naked eye – every star they can see between (but not including) the 'box' made by the constellation's four celestial cardinals. More stars are likely to be visible in areas of lower light pollution, and vice versa, thus building a picture of night sky quality across the country.

Orion, showing the cardinal stars. Star Count is asking observers to count and log the number of stars they can see within this box – likely to be a lot less to the naked eye than captured on this DSLR camera.
Photograph by Sl1990, Pixabay

Location, location

Inspiring the public to reconnect with the heavens is an admirable motive, but really the Star Count campaign is designed to measure how light levels are changing across the country. In 2015 CPRE measured the quality of the night sky across Britain using data from an American weather satellite. The results indicated England in particular was suffering a severe case of what it terms 'night blight:' the spill of human light from sources such as floodlights and streetlights. This light pollution reduces the sky's clarity and, according to some research, the wellbeing of the living things beneath it – for reasons more insidious than simply seeing fewer stars after sundown.

“Our maps revealed that just 22% of England has pristine night skies completely free of light pollution,” says Marrington. “By comparison, in Wales, it is 57% and the fortunate folk in Scotland have an amazing 77% of the very darkest skies.”

“I’ve been looking at the sky at night for over 50 years,” says Bob Mizon, of the British Astronomical Association's Commission for Dark Skies. “In that time, through the decades of sodium light with its deep orange glow to modern whitish LEDs – normally far too bright for the lighting task – I’ve seen the stars gradually disappearing in most parts of the UK.”

“We need lights at night,” he says, “but in the right place and at the right time, without over-lighting and spoiling the night-time environment.” 

The Campaign to Protect Rural England's website features interactive maps displaying the quality of Britain's night skies on a scale of radiance.
Photograph by Cpre, Natural England

World-class skies

Despite its dense population as a whole, parts of Britain – such as Wales and the Highlands of Scotland – have very low light pollution due to sparse habitation. Sutherland, in Scotland's far north, has a population density of just 5 people per square kilometre. The UK has five dark sky parks and five areas in the UK have been designated as Dark Sky Reserves: The Brecon Beacons, Exmoor, SnowdoniaCranborne Chase in Wiltshire, and Moore's Reserve in the South Downs – named for the late astronomer Sir Patrick Moore. The latter five join a global total of just 13 such areas where the clarity of the night sky, and the proactive efforts of those beneath to preserve it, meet the standards of the Arizona-based International Dark Skies Association

But while these rural areas benefit from lower population densities, in the city the situation is rather more hazy – where industrial lighting, lights that are poorly angled or persistently on throughout the night have unwanted effects on those close by. “Well away from the city lights in the darkness, you might see over 3000 stars in the night sky, and the faint oval blur of the Andromeda Galaxy, whose light has taken more than 2 million years to get here,” says Bob Mazin. “From the average suburb, because most of its lights are either poorly directed or too bright, you might see a couple of dozen stars.”

“We need lights at night – but in the right place and at the right time.”

Bob Mizon, British Astronomical Association

“Light pollution has serious health impacts when it affects our sleep patterns by shining through our windows at night.” continues Emma Marrington. “This disrupts how our bodies make melatonin, the brain hormone we need to reset our biological clock. Nature’s impacted too, as birds, insects and other animals are interrupted when trying to feed, breed, or migrate at night.” 

Research into light pollution is ongoing, as are methods intended to help ease it. But wherever you are, there's a sky above you – so this could be your chance to see just how dark the sky above your neighbourhood is compared to the rest of the UK. 

Light Pollution 101
Ever since the light bulb's invention 150 years ago, artificial light has illuminated homes, streets, and skies -- but with some unintended consequences. Learn about the major types of light pollution, their impact on human health, and how the worldwide glow from artificial light may continue to grow.

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