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.
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.
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.