My God, it’s full of stars!

I saw a shoot­ing star last night as it streaked across a sky full of stars. I kid you not! You could look up and see thou­sands of stars. Now, astro­nomy mavens might not be too impressed by that. Many people can see stars as dim as mag­nitude six in a dark sky, lucky people can see dim­mer stars. There accounts for around 6000 vis­ible naked-eye stars. But for many of us that’s simply not true.

I used to live in a sub­urb of Derby. When I moved to Powys I noticed there were more stars in the sky. A lot more. So many I was temp­ted to buy a tele­scope. The next 30 days were clouded out, so that killed that idea, but on the days when stars are vis­ible they’re stun­ningly impress­ive. There is a way to quantify how impress­ive the night sky is that you can help with next year.

Orion in the night sky

Orion, the Hunter by Eduardo Mariño.

When I was in Derby I took part in GLOBE at Night. It’s a sur­vey that asks you to describe what you can see. The ver­sion I took part in asked people to say which stars they could see in Orion, the image on the right. It’s a good choice because the belt makes it easy to identify. I could see those. I could also see Betelguese (top-left), Bellatrix (top-right) and Rigel (bottom-right). If I squin­ted and stared hard I could ima­gine I could see Saiph (bottom-left), but really I couldn’t. There was a sodium glow of dank yel­low reach­ing up into the sky like lurid phlegm-coloured fog. It was the first time I’d real­ised how bad the local light pol­lu­tion was. In con­trast, I can’t account for every star in the photo shown, partly because as your eye dark-adapts you see more stars. However, this image is a very good impres­sion of what I saw. I had no trouble at all see­ing Orion’s belt. It didn’t look like a fig­ure of gems on a vel­vet back­ground. Instead the major stars looked like gems over a back­ground where someone had sneezed dia­mond dust.

It’s pos­sible this long-term cold I’ve had since September is affect­ing me more than I think.

The dif­fer­ence isn’t just in quant­ity. A dark sky makes a big dif­fer­ence to the qual­ity of the sky. I thought I knew my way around the night sky pretty well. Last night I could see Orion out of my win­dow, but took a little while to find Taurus. Again, a good ama­teur astro­nomer might find this funny. Taurus should be unmiss­able. Even more so when you have a dark sky, mak­ing the stars even easier to see. In the Northern hemi­sphere you look a little way to the right and you’ll see the horns of Taurus the bull live a V shape. Aldebaran sits at the top of one of the horns. This V is made of bright stars, it’s the most vis­ible part of the con­stel­la­tion, it is strik­ing. But when you have a prop­erly dark sky it’s strik­ing among a whole load of other stars. In Derby Taurus was to the right of Orion. In Powys it still is, but this time there’s an awful lot of stars in between them. It’s easier to find your when around the night sky when you can only see the prom­in­ent stars. Here, it’s almost like the sky has developed a glit­ter­ing inter­fer­ence pattern.

I know that light pol­lu­tion has been a topic of pain for astro­nomers for dec­ades. In my head I can fully under­stand it as a quant­it­ive argu­ment. Dark skies = more stars. That might not be enough for a power­ful emotive argu­ment. Imagine you live some­where where the night sky is rub­bish. Reducing light pol­lu­tion isn’t such a big deal. It just means more rub­bish look­ing stars. I also won­der if heavy light pol­lu­tion, which is worst nearest the hori­zon, helps dis­tance people from the Cosmos. Banishing the vis­ible stars to the highest parts of the sky emphas­ise the sep­ar­a­tion between earthly life and the rest of the uni­verse. A dark sky shows that where you are is the place where the Earth meets the Sky. Below you soil, above only the unima­gin­able heights to the edge of the uni­verse, and you smack in the middle.

That feels dif­fer­ent and it’s some­thing you can’t repro­duce in a planetarium.

Photo: Orion by Eduardo Mariño. Licenced under a Creative Commons BY-NC-SA licence.

As a coda, I remem­ber read­ing about the after­math of Hurricane Andrew in Astronomy magazine. After the power had been cut the night sky was exposed. People phoned up local uni­ver­sit­ies, plan­et­aria and obser­vat­or­ies to ask what the lights in the sky were. At the time I lived in the coun­try, so I found the idea that people could be puzzled by stars hil­ari­ous. Having lived in a city now, and know­ing that many people have never lived any­where else I have a lot more empathy. Imagine liv­ing through a hur­ricane and then, for the first time in your life, the uni­verse arrives on your door­step. No won­der you’d want to phone someone to check it’s normal.


When he's not tired, fixing his car or caught in train delays, Alun Salt works part-time for the Annals of Botany weblog. His PhD was in ancient science at the University of Leicester, but he doesn't know Richard III.