Stellar archaeology

Dr Emma Chapman speaks to Harry Lewis about stars dating back 13 billion years...

Harry - Emma, I hear you never actually wanted to be an astrophysicist at all. Instead, you wanted the job in Egyptology hunting for tombs and learning Egyptian. I want to say it didn't work out, but in your new book, I came across a chapter called stellar archeology, which might make me think otherwise. This isn't an actual discipline is it? This is something that publicists have thought up to make a good soundbite!

Emma - No, this is is a real scientific field full of cutting edge technology and well, incredibly excellent research carried out by scientists called stellar archeologists. I'm very, very, very jealous of their name and what they do is they try and uncover the first stars that existed in our universe that have survived and are just knocking around the neighbourhood today.

Harry - Knocking around the neighbourhood today. I mean, you're gonna have to tell us a little bit more because you've peaked my interest.

Emma - So we think that if the first stars, if there were some stars that were small enough, because the bigger the star, the faster it fuses through its fuel, the bigger star the greedier it is, the quicker it explodes basically. So if we can find some small first stars, then they might have survived the whole 13 billion years and still be around in the Milky Way. The problem is that they have been through a 13 billion year timeline of stuff, being chucked at them of pollution, basically of what I just referred to of all these heavy elements like lithium, beryllium, boron, silicon, all of these things that were created as the universe went along, they're camouflaged. So stellar archeologists, the job is to look at the light from, let's say, several hundred billion stars in the Milky Way and dust it off dust off this light to figure out what is the pollution and what is a real first real pristine, really clean star, lying under all of that. That could be one of these first ever stars to exist.

Harry - And how does one go about choosing where to look? Because I'm assuming you must have masses of data if you point your telescope anywhere. So where do you try and find these, what you would've thought are extinct stars?

Emma - Telescope time is money. It costs a lot of time and patience to get any time on the telescope reserved. And it's 10,000 pounds a night or more. So you have to know where to point and the best guess we can really have is that we know that the stars tend to migrate out of the disc of the galaxy into the halo of the galaxy. That's a good first starting point. We can just look in the halo and that's indeed where we do tend to do most of our observations at the minute, but there's still tens of billions, hundreds of billions to go through. So it really is a case of griding up the sky of just meticulously searching for that that hidden treasure as it were. This is why it all links back to Egyptology for me, because it's the same kind of thing. What people will never tell you about. For example, the discovery of Tutanhkamun's tomb, Howard Carter didn't just stumble across it on his first go. He was there for five years having grided out the desert patch that he'd got permission for. It was on his last dig, as in his funding was about to be cut off that he found this treasure and it really is the same kind of thing for this stellar archeology. We have to be meticulous. We have to grid off the sky, use an educated guess, but it's gonna take time and grit.

Harry - Do you think it'll be successful? Do you think you will find one of these stars?

Emma - I think so. As a scientist, I can only give my well educated guess, but we are getting so close. We've managed to find a second star, if you will. So a star that has so few heavy elements in it that it has to have been from a very, very early time in the universe. And we believe that star is kind of the first descendant in that it was formed from the gas, from the explosion of a first star. That all makes sense. So the point is we're getting really, really close now and our technology is improving all the time. So I have a lot of hope for the next decade for this field.

Harry - And Emma, how do we look back in time and observe these first stars?

Emma - Well, the great thing about light is that it has a speed limit, which means that it takes time to travel. So when we look at the sun, don't look at the sun, but when we look at the sun, then the light from the sun is about eight minutes old. It's taken eight minutes to get to us. So we're seeing the sun as it was eight minutes in the past. When we look at light from the nearest galaxy, we are seeing Andromeda 2.5 million years in the past. So what we do, what I do as a day job is I use radio telescopes to tune into radio light that has been traveling to us for 13 billion years. So we can see the universe as it was 13 billion years ago and pick up the light from this era of the first stars and learn all about it. In real time if you will, it's not through simulation, it's through watching.

Frans - I have a small question.

Harry - Yeah, go Frans.

Frans - In a country notoriously cloudy like the UK, the telescopes must have a bit of trouble or do carry out your observations in Patagonia or some other place?

Emma - This is why I'm a radio astronomer and why radio astronomy really flourished in the UK. Radio waves can penetrate clouds, dust a lot of the atmosphere a lot more than the optical telescopes and so we can observe day and night.