Using balloons to see Dark Matter

14 September 2015

Interview with

Richard Massey, Durham University

One of the big mysteries space scientists are grappling with concerns 'Dark Matter'. It is thought to make up about twenty percent of the mass in the Universe, but we can't see it.Hubble_space_telescope We know it exists, however, because we can see the effects it has on other objects like stars. To understand it we first need to plot where it is so that we can attempt to detect it. One way to do this is to use the Hubble Space Telescope. But the queue to use this instruments is astronomical, so Richard Massey from Durham University has developed his own approach. He is using a helium balloon to carry a telescope aloft to the edge of space. Sam Mahaffey caught up with him down the line from Canada, where he's busy preparing for launch...

Richard - Dark matter is this weird stuff that's out there in the universe. In fact, it's the most common stuff in the universe and it's the heaviest stuff there is. We know it's there because all of that mass and all of that gravity pulls around things that we can see. And so, the stars in the Milky Way are spinning around and around because there's dark matter. But unfortunately, the dark matter itself is invisible. So, we can't see it directly. We have to infer it's there because of the way it moves things we can see. To be honest, it's become a bit of a mystery, almost the biggest mystery. We just don't know what this stuff is and we're trying to find out.

Sam - If it's so hard for you to observe, how do you study it?

Richard - The best way that we found to look at dark matter is a technique called gravitational lensing. The idea of this is that you don't look at the dark matter itself. You can't because it's invisible, but you look at something behind it. The effect of this is like looking through a sort of a funhouse mirror or looking through a bathroom windowpane. When light doesn't travel in straight lines then the object behind it appears a bit distorted. So when you look out of a bathroom window, the street lights on the other side of the road look all wobbly and they don't look light shaped. When we look past them (dark matter), the galaxies behind it don't look galaxy-shaped. They look all distorted and stretched. We can infer from that that there must be something very heavy in front of them. If we can't see anything, it must be this dark matter that's invisible. If we have a telescope in space, like the Hubble Space Telescope, then we get a perfect view of them and we can measure their shapes and look how distorted the light is.

Sam - But you're going to some really quite extreme lengths to observe dark matter when you could just use the Hubble Space Telescope.

Richard - Well, we've used the Hubble Space Telescope for this kind of stuff before and it's a fantastic instrument. Unfortunately, there's a long waiting list to use the Hubble Space Telescope. Everybody wants to have a go and we basically got sort of bored waiting and said, "Wouldn't it be nice to have our own satellite, our own telescope in space?" unfortunately, in these times of austerity, we can't afford a whole satellite in space. But we got inventive and thought, Well, we can get 99 per cent of the way into space with a big helium-filled balloon. If we sling a telescope underneath that. Well, we're above basically all of the Earth's atmosphere, but it's a lot cheaper, a lot easier, and so, that's what we've done. It's going up to about 100,000 feet. That's about 3 times higher than a plane and it goes straight up. It can lift a lot of weight including our telescope. Now the big problem about putting a telescope underneath a balloon is that you got a great big balloon then a sort of 100-meter long rope and then a telescope swinging around underneath it. As this telescope swings backwards and forwards, of course, it's moving around, it's pointing at different places. So, the clever thing that we'd have to do is to develop a way to keep the telescope pointing in the same direction. So, we've got this whole sort of series of gimbals that sort of rotates so that the telescope itself is held within several concentric cages. As the sort of gondola that it's in swings around, the telescope itself uses some gyroscopes to stay pointing in exactly the right direction.

Sam - But what happens to the balloon and what happens to the telescope when you're finished? Could it just come crashing down to Earth and land on somebody's head?

Richard - Well, that's sort of part of the problem with this is, the balloon that we're about to launch is going to go up just for 24 hours. It's then going to come down on a parachute and hopefully, survive. Now, not all of them do survive that half of the time, you need to do some repairs and sort of 1 in 5 times, enough of it comes down that you have to basically rebuild it.

Sam - And now you've got NASA's approval, might we detect some dark matter very soon?

Richard - We've got the flight now to test that everything works and we're booked in for a long duration balloon flight to do lots and lots of science and look for lots of dark matter, and other things. That's going to happen in 2017. So, we've got a few months to do some repairs and maybe upgrade the odd camera here and there, and then get ready to send it up and start looking for dark matter.

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