Best place to stargaze on Earth

Where on Earth can you get the best view of the heavens?
04 August 2020

Interview with 

Matt Bothwell, Cambridge University


Someone shining a light up from a mountain at the stars and Milky Way.


If you like looking at stars and other heavenly bodies in the night sky you’ll know that using your telescope in a city or other place with lots of light pollution is not a good idea. It’s better to get out into the countryside where the further you are away from street lights and vehicle headlights the better. Taking it to an extreme though, you are going to have put on your thermal underwear and hiking boots. A few huskie dogs might come in useful too! That’s because Chinese astronomers have discovered that the best place on Earth to stargaze is in Antarctica. It’s on top of a mountain of ice called Dome A, and it’s 12 hundred kilometres from anywhere. Astronomer Matt Bothwell has been reading the research and he told Phil Sansom what makes this spot so special...

Matt - It's a general problem for astronomy that we are living at the bottom of a very thick atmosphere. I mean, it's nice for human life on Earth that we don't all die! But for astronomy, it's quite difficult that all the nice signals from space have to travel through hundreds of miles of air before they reach our telescopes. And air isn't perfectly transparent, right? Anyone that has seen a mirage wobbling around or seen light wobbling around above a heat source, like a radiator or a fire, will get the idea that light can bend and twist as it travels through air.

Phil - That's why the stars twinkle, isn't it?

Matt - Yes, exactly right. That's why stars twinkle. Astronomers called this "seeing", which is a fairly obscure word. don't know why we call it this! But yes it's the seeing is what we call the amount that light is kind of blurred as it travels through our atmosphere. And the real trick for astronomers is to find places where the seeing is really, really good, where the atmosphere is nice and calm and still. And we can take very nice, clear pictures of space.

Phil - That's why astronomers like Hawaii, for example, right? Or big high mountains. Isn't it?

Matt - Exactly. So Hawaii is famously good for this. The Atacama desert is famously good for this. And what this new paper has found is that there's this particular site in Antarctica called dome A where the seeing is maybe better than anywhere else on planet Earth.

Phil - How much better?

Matt - Astronomers measure seeing in something called arc seconds. An arc second is a very, very, very tiny angle. So one arc second is 3,600th of a degree. And it's basically how much the light from a star or light from a galaxy has been spread out by the atmosphere. If you have seen below one arc second, that's generally considered pretty good. Down here in Antarctica in dome A, the seeing gets as good as around 0.1 arc second, which is absurdly good. Much, much, much better than anything you would ever see in Hawaii or Chile.

Phil - Is this sort of like a measure of how blurry the stars are when you look at them? And so this place, if you look up to the stars, they're 10 times clearer than this gold standard?

Matt - Yes, that's exactly right. So 10 times clearer to our telescopes.

Phil - Where is this site exactly?

Matt - So it's called dome A, it's in the Antarctic. I think it's relatively close to the very slap bang center. It's essentially one of the highest points in Antarctica and about four kilometres above sea level.

Phil - What would this make a difference for? What kind of thing would this be useful for?

Matt - Okay. So I would caveat this with the fact that I'm a long wavelength radio astronomer. I don't really do much short wavelength like optical astronomy type stuff. But getting better resolution in telescopes is all about being able to see objects that are close together. And so two binary stars, for example, might blur into one, if you have bad seeing, but with this crystal clear seeing, you'll be able to separate them and see that they're actually two separate stars. Or exoplanets, for example. So planets orbiting other stars, is one of the really hot topics in astronomy nowadays. We want very, very, very good resolution to be able to separate out systems like that.

Phil - Is it really worth carting a whole bunch of really expensive telescope materials out to this isolated part of Antarctica? I mean, is this sort of untamed wilderness, are there already people there, or what?

Matt - I would say it's, it's a lot closer to untamed wilderness than almost anywhere else on Earth. Building anything down in Antarctica is going to be a very, very substantial thing to do. But I do think it's going to be worth it, for a given value of it's worth it, right. Getting a telescope to the best place in the world to observe the universe would be very, very valuable.


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