Science Interviews


Mon, 14th Sep 2015

Using balloons to see Dark Matter

Richard Massey, Durham University

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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 heís busy preparing for launch...

Richard - Dark matter is this weird stuff that's out there in the universe. In fact, itís the most common stuff in the universe and itís the heaviest stuff there is. We know itís 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 itís there because of the way it moves things we can see. To be honest, itís become a bit of a mystery, almost the biggest mystery. We just donít know what this stuff is and weíre trying to find out.

Sam - If itís 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 donít look at the dark matter itself. You can't because itís 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 doesnít 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 donít look light shaped. When we look past them (dark matter), the galaxies behind it donít 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 thatís 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, weíve used the Hubble Space Telescope for this kind of stuff before and itís 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, ďWouldnít it be nice to have our own satellite, our own telescope in space?Ē 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, weíre above basically all of the Earthís atmosphere, but itís a lot cheaper, a lot easier, and so, thatís what weíve done. Itís going up to about 100,000 feet. Thatís 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, itís moving around, itís pointing at different places. So, the clever thing that weíd have to do is to develop a way to keep the telescope pointing in the same direction. So, weíve 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 somebodyís head?

Richard - Well, thatís sort of part of the problem with this is, the balloon that weíre about to launch is going to go up just for 24 hours. Itís 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 youíve got NASAís approval, might we detect some dark matter very soon?

Richard - Weíve got the flight now to test that everything works and weíre 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. Thatís going to happen in 2017. So, weíve 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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