Planetary Radio: Space Exploration, Astronomy and Science - Exploring The Mystery of Dark Matter with Richard Massey

Episode Date: May 21, 2007

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The Dark Mystery of Dark Matter, this week on Planetary Radio. Hi everyone, welcome to Public Radio's travel show that takes you to the final frontier. I'm Matt Kaplan. What is it that can't be seen seen but makes up most of the universe? Doesn't shine or reflect but bends light? Reshapes galaxies but whose composition is a mystery?

If you know the answer, there are a few thousand scientists who'd love to hear from you. In the meantime, they learn what they can about dark matter by mapping its distribution in distant realms of the cosmos.

Richard Massey of Caltech was one of the first to use gravitational lensing to create such maps. He'll join us to comment on the most recent announcement about dark stuff made just a few days ago. Emily is here, too. Ms. Lakdawalla answers a question about the Magellan spacecraft now settling into orbit around Mercury in the most indirect fashion imaginable. And Bruce Betts points out the bright lights above our heads in this week's What's Up. He'll also reveal how many of those lights are rocks that get uncomfortably close to our little planet. That number will win a Planetary Radio t-shirt for another trivia contest entrant.

Speaking of trivia, what happened on May 21st, 1927? That's right, it was 80 years ago that Charles Lindbergh made the first solo transatlantic flight. And 80 years later to the day, SOFIA was dedicated by his grandson, Eric. SOFIA is the Stratospheric Observatory for Infrared Astronomy, a nearly 100-inch telescope mounted in a 747 aircraft. It will soon begin flying at 40,000 feet and higher, above 90% of the Earth's atmosphere, and almost all infrared-absorbing water vapor. Stay tuned for images. Shuttle Atlantis has returned to Pad 39A. You may remember that the ship had to be rolled back to the Vehicle Assembly Building after it was damaged by a freak hailstorm.

Not all the patchwork is pretty, but NASA believes it is ready for a June 8 launch. Lastly, where on Earth would you go if you wanted to learn how to find life in the ocean on Jupiter's moon Europa? How about the world's deepest sinkhole? A little robot named DepthX is descending about 1,000 feet to poke around at the bottom of Mexico's Cenote Zacaton. You can read about this university-sponsored mission and see a picture at planetary.org. That's where you'll also find Emily Lakdawalla's blog, where she has written about preparations for the launches of the Dawn asteroid mission and the Phoenix Mars lander.

In the meantime, here's her latest Q&A contribution. I'll be lost in the dark with Richard Massey in just a minute. Hi, I'm Emily Lakdawalla with questions and answers. A listener asked, Why does Messenger need so many gravity assists to get to Mercury? Just because Mercury is relatively close to Earth doesn't mean it's easy to put a spacecraft into orbit around it. The main problem is that Mercury is also very close to the Sun.

If a spacecraft launched directly toward Mercury from Earth, it would also be diving toward the immense gravity well of the Sun. The spacecraft would travel so fast when it got to Mercury that it would have no hope of slowing down enough to be captured by Mercury's gravity. In order to get to Mercury and stay there, the Messenger spacecraft has to systematically shrink its own orbit around the Sun and reduce its momentum, winding up with an orbit nearly matching Mercury's. From start to finish, Messenger's journey requires six gravity assists.

How will those work to match Messenger with Mercury? Stay tuned to Planetary Radio to find out. Just when you think you've got the universe figured out, along comes something like dark matter. And hey, don't even get me started on dark energy. Maybe this is what Darth Vader meant when he said, we do not understand the power of the dark side. Mysterious though it may be, we're learning how to find it. Here's astronomer James Gee of Johns Hopkins University just last week. Today we are reporting our discovery of a ring-like dark metal structure in one of the most famous galaxy clusters called the CL002417.

No such kind of structure has been reported in the past, and we believe this is the strongest evidence yet for the existence of dark matter. James Gee at a NASA-sponsored press conference last week, Richard Massey participated as a commentator, not directly involved in the discovery of that colossal ring of dark matter. He was a good choice. As a postdoctoral research scholar at Caltech in Pasadena, California, Richard was one of the first to use gravitational lensing to find and map the stuff.

He graciously agreed to talk with us while on the road. As we speak, you are in Dallas? Yes, I've been at a conference all week at Texas A&M University. When you had said in email that you might be driving across Texas, I was afraid you would be in that vast wasteland of West Texas, which, in my opinion, if there was any place you would look for dark matter on Earth, that would be the place. It's certainly a very long way.

Can you tell us a little bit about this announcement that was made last week at the media briefing, which you participated in as someone who was asked to make impartial comment? Right, yes. So I wasn't involved in the team that produced the results, but what they made was a very sort of exciting attempt to discover something about dark matter. Really, any attempt or any result about dark matter is inordinately exciting at the moment, just because we know so very little about it. All we know is that the matter in the universe that we sort of know about, everything that we can touch and

see and feel, everything around us is just not the whole story. There's more to it than that. For every lump of ordinary matter, there's about six times much of this mysterious, invisible substance that we don't know much about, except the fact, basically, that it's invisible. And we therefore call it dark matter. And it is invisible because it doesn't react electromagnetically with anything else. That's exactly right.

Things shine and even reflect light. All that is governed by the electromagnetic force. Dark matter, we know, just doesn't interact via that force. In fact, it only interacts via the force of gravity. We can only sort of see it by its indirect gravitational effect on other things. Just like the Earth orbits around the Sun because of the Sun's gravity

and that we stay on the Earth because of its gravity. If you've got a lump of dark matter in one place, then things will orbit around it and be sort of deflected and move because it's affected by the gravity of this dark matter. So this team, led by M. James Gee of Johns Hopkins, made this announcement last week of their discovery of a ring of dark matter. Yes, this was seen in a collision between two giant clusters of galaxies. These collisions are really important to astronomers

because they're basically as close as we can get to throwing stuff around in a lab and seeing what happens when stuff bangs into each other, like particles, for example, in joint particles. So this was in two clusters of galaxies which had just collided. And the dark matter in that, because of the sort of gravitational interaction between these two clusters as they slam into one another, it was thrown off in a shell. Dark matter, it's like a sort of a ripple in a pond

that one galaxy cluster has gone through another, and it's flung off this shell of dark matter, which we see sort of end on as a ring. And so they've mapped out this ring of dark matter. So there really can be no doubt, based on this research and your own research that we want to get into,

that this stuff is really out there. Yeah, the evidence now is mounting. There are still opponents to it, of course, but really we're now seeing the gravitational signature of matter in it, something that traces all of the mass of the universe behaving very differently and coming in different places to the distribution of light or ordinary matter.

So we really do see mass in places where there is no ordinary matter. That's the dark matter. If we wanted to look for local effects of dark matter, could we even possibly find them, or do you have to look for them on the scale of objects like galaxies? Yeah, well, I mean, it's just the problem with dark matter is that you can only see it through its gravitational effects, so you automatically need to have a lot of it. Typically, astronomical techniques have to involve very large scales and very large amounts of gravity for it to be even detectable. There is, however, the possibility that we might eventually be able to see it

in particle accelerators on Earth, that the next generation of particle accelerators might, in fact, be energetic enough and collide particles at sufficient speed to generate some of our own dark matter, just a very small amount of it, but that we could see ourselves. And there I'm sure you're talking about the Large Hadron Collider, which we've talked about previously on this show and will be turned on within a matter of weeks. Well, there's actually been a slight setback.

Oh. within a matter of weeks? Well, there's actually been a slight setback. Oh. To get the particles spinning in the circles to slam into each other, you need a series of magnets to basically make the particles go in a circle, sort of to deflect them on a straight line.

And during some initial tests of these magnets, they actually have to be cooled down because they're superconducting magnets. And while they were being cooled down, some of them broke. This has been a bit of a setback to the program. It's not quite going to be turned on in the next few months. However, the initial estimates are that it's terribly serious that everything's going to be fixed. Everything hopefully can be brought online next year, which is actually in line with initial expectations.

It's basically going to skip an engineering sort of trial run. The patients are basically going to skip an engineering sort of trial run. I assume that any kind of delay, though, must be frustrating to scientists like yourself, particularly theoreticians who have been looking for evidence of all kinds of strange things, including this famous particle, the theoretical particle, the Higgs. In your mind, is there any relationship between dark matter and even more recently postulated and I guess discovered dark energy? Well, the sort of similarity in their name, they're actually very opposite. They sort of have an opposite effect. One repels and one attracts.

Exactly. There's this giant cosmic tug of war going on as to what the eventual fate of the universe will be. If dark matter has its way, it will end up in a big crunch and everything will collapse back into a singularity like it came from at the Big Bang. And if dark energy wins, the universe will keep on expanding

at an accelerating rate until it eventually rips itself apart in a sort of giant tearing. Is it meaningful to say that we know anything more about dark matter than we do about dark energy? At least you're able to map dark matter to a degree. Yeah, exactly.

It's a bit more familiar. It at least behaves in some way gravitationally. It behaves in a similar way to the stuff that we're familiar with. And so we've got a bit more of a conceptual feel for it. And also then we've got things like we can map it out using astronomical techniques and stand a chance of detecting something in a lab in the Large Hadron Collider. Dark energy, on the other hand, is just completely very different. We don't even know whether to think of that as a substance

or some sort of modification of gravity and equation. We really have no idea what on Earth dark energy is. Doesn't this make life much more interesting and perhaps exciting for folks working in this field? Actually, I really like the idea of dark matter. It's a bit more tractable. Maybe I'm not aiming high enough. That's Richard Massey of Caltech. He'll return to tell us more about the dark matter of dark matter in a minute.

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Members receive the internationally acclaimed Planetary Radio listeners who aren't yet members can join and receive a Planetary Radio T-shirt. Members receive the internationally acclaimed Planetary Report magazine. That's planetary.org slash radio. The Planetary Society, exploring new worlds. Welcome back to Planetary Radio. I'm Matt Kaplan. Our guest is Richard Massey, a postdoctoral research scholar at the California Institute of Technology. a postdoctoral research scholar at the California Institute of Technology. He and others are beginning to reveal the secrets of dark matter through its gravitational influence on light. I wanted to learn more about another team's discovery of a ring of the mysterious material

apparently formed by the long-ago collision of two clusters of galaxies. This work that was announced last week, does it have that relationship to your work of mapping the presence, the distribution of dark matter in the universe? There have been several maps of dark matter produced recently, and all of them use the same fundamental technique. And that is of gravitational lift. I've said before that we can only detect the dark matter through its gravitational effect on other things. And it has a gravitational effect on everything, not just matter, but even light,

because gravity is really just a sort of a bending of space-time. As Einstein told us, yes. Yeah, exactly. And so if space bends, everything in it bends, even paths of light, even the sort of straight lines that light would follow. So light doesn't actually travel in straight lines. There's sort of straight lines that light would follow. So light doesn't actually travel in straight lines. There's sort of trick number one.

And so what we do to sort of detect this is to look at galaxies, very ordinary galaxies. They're only special in that they're very far away. We look at galaxies a really long way away behind any dark matter that we're interested in. And they act as a sort of backlight to this dark matter. We almost see the dark matter in silhouette. The light from these distant galaxies becomes fainter. The light from very distant galaxies behind dark matter gets bent by the dark matter as it passes from them to Earth. It's like looking through a magnifying glass. If you look through a magnifying glass, very distant text would become a bit bigger and also slightly sort of bent at the edges. There's straight lines on a page that just bend up. Well exactly the same effect happens when light from distant galaxies

gets bent by intervening dark matter, that they become slightly bigger and brighter, but also slightly bent and we can detect the dark matter by looking for distortion in the shapes of galaxies behind the dark matter. It's like using a, rather than using a magnifying glass to study text a long way away, it's like using the text to study the magnifying glass. By looking at how, it's all the wrong way around, if you like, but by looking at how bent some text on a page would be, we can figure out how much transparent glass there is between the text and us. In exactly the same way, we can see how much dark matter there is between us and different galaxies.

Almost like reverse engineering. Yeah, exactly. Does dark matter behave much like regular matter would, at least gravitationally? I mean, is the distribution what you would expect to see if this was all just nebulas made of gaseous hydrogen? In terms of its gravity, yeah. As far as we can tell at the moment, it behaves in exactly the same way. And that's one of the interesting bits about it. But where it behaves differently is through the other forces.

So it doesn't have friction. For example, if you put your finger into some of it, then you just wouldn't notice. And so because it doesn't interact in ways other than gravity, that we can start to detect where it is. So for example, when these clusters of galaxies collide, the ordinary matter slows down. The ordinary matter in both galaxy clusters sort of hits each other and ends up slowing down and stopping near the point of impact. But a dark matter, because it doesn't interact in that way, just keeps going. It keeps going and it ends up further away from the point of impact than the ordinary matter.

And so it's how it behaves differently because of the other forces that we know is there. Ignoring any benefit that may come from the LHC when it is up to full power, and hopefully it will make some wonderful discoveries. What can the current research mapping dark matter, is there a chance that it will help us to begin to understand what it may actually be composed of? Right. Well, the problem is that at the moment the theoreticians have had a field day for a few decades.

There's been no data, so there's come up with so many possibilities and models and ideas of what it might be. It's hard to narrow down the field. Rather, like you say, they really need some data rather quickly. So there are lots of models. What the initial data can do is measure a few of the gross general properties of the dark matter. can do is measure a few of the sort of gross general properties of the dark matter. For example, what its interaction cross-section is, that it means how much it interacts with other things.

As a rule, we think it doesn't interact at all, but it might perhaps have a very slight amount of interaction through forces of gravity. We can measure that, and we can possibly measure the mass of individual particles. And these will start to cut down on which of the models the theoreticians have proposed and start to rule out some of the possibilities. What is the nature of your current research in this area? So I've been using the Hubble Space Telescope, like all of these, to map out a very large area of sky, which is basically picked at random

so that it's just a representative sample of the universe. And it turns out to contain no particular objects of interest themselves, except that it sort of captures the whole sort of large-scale structure of the universe. And we see this whole filamentary web of matter structure with sort of crisscrossing and filaments, which forms a scaffolding on which the ordinary matter can later sort of crisscrossing wood and filament, which forms a scaffolding on which the ordinary matter can later sort of condense and then fall into under gravity. And it's after this

scaffolding in which everything else is built. Well, the universe proves to be a more and more interesting place the more we learn about it, and your work is certainly furthering that. While we are out of time, I hope that particularly when the LHC does come online and work up to full power, and as the work that you're doing with Dark Matter,

observing it, if one can call it that, continues, I hope that we can give you another call. Yeah, that would be great. We're certainly planning lots of exciting things for the future, so we're looking forward to it. Thank you so much, Richard. Certainly planning lots of exciting things for the future. So we're looking forward to it. Thank you so much, Richard. Richard Massey is a postdoctoral research scholar at the California Institute of Technology,

better known as Caltech. Did some of the first work on the mapping of dark matter in our universe, work that continues and is underway by a number of teams around our little globe. We'll be right back with Bruce Betts and the view of the night sky from that little globe in our regular What's Up visit. That'll be right after this return visit by Emily. I'm Emily Lakdawalla back with Q&A. How will MESSENGER use its six gravity-assist flybys to reach Mercury?

When MESSENGER was launched, its orbit was very similar to Earth's, taking one year to orbit the Sun at a distance of one astronomical unit. To match orbits with Mercury, MESSENGER needs to shrink the size of its orbit by almost 60%, increase the tilt of its orbit by 7 degrees, and rotate the orientation of its orbit to match Mercury's very elliptical path. MESSENGER has completed two flybys, one each of Earth and Venus, which have shrunk the orbit by about a quarter and finished most of the required tilting. There will be one more Venus flyby and finally three separate Mercury flybys to complete the necessary orbit shrinking.

Even with a seven-year journey and six separate gravity assists, Messenger will still need to burn a third of the total amount of onboard fuel it launched with to enter orbit in 2011. Why hasn't this been tried before? Because mission designers didn't discover the possibility of this multiple gravity assist path to Mercury until the mid-1980s. And MESSENGER is the very first mission to take advantage of it. Got a question about the universe? Send it to us at planetaryradio at planetary.org.

And now here's Matt with more Planetary Radio. Got ourselves Bruce Betts on the telephone. He's here for What's Up, our weekly review of the night sky and a new trivia contest and other cool stuff. How are you doing? Doing pretty well. How about you, Matt? I'm okay. I'm okay. I hope people can't hear this nasty buzz in the background. We've got a bad phone line and we can't get rid of it. Are you sure it's not insects in your ears again?

Let me check. Well, yeah, it is, but it's the phone line too. Oh. I'll just try to speak enthusiastically. Yeah, please do. And it doesn't interfere with my vision, so tell us about the night sky. Fantastically. Yeah, please do.

And it doesn't interfere with my vision, so tell us about the night sky. In the night sky, in the evening, of course, Venus, even if you have problems with vision, you can probably see Venus. Venus was lovely recently next to the full moon, still up there looking like a really, really, really bright star in the west in the early evening. And watch over the coming weeks as Saturn, which is up above it in the night sky, will start growing closer and closer to Venus until in about a month or so. They will nuzzle right next to each other, and we'll keep you posted on that. But obviously Saturn up above Venus.

We also have Saturn, if you catch this as soon as this comes out, can still catch Saturn close to the moon on May 22nd. Look for the bright yellowish star, but much, much dimmer than Venus. Jupiter also getting fun and easy to see. You can check it out in the early evening nowadays over there in the east, and it is approaching opposition on june 6th that means it will be on the opposite side of the earth from the sun and therefore rising around sunset and setting around sunrise and in the pre-dawn sky jupiter will still be up and mars will also be

up in the east still kind of dim and reddish and slowly, slowly, slowly making its way up in the sky. Was that Venus that I saw near the moon just a couple of nights ago here? It was indeed. Wow, was it beautiful. I mean, in our bright LA sky, you couldn't see any stars to speak of, but you could not mistake the moon with this beautiful big Venus hanging below it. And you know what you don't want to miss if you like that? What's that? On May 31st, go out there, look to the other side of the sky over there in the east, and the moon will be snuggling up with Jupiter.

Yeah. Looking nearly as stunning. Oh, this is a good month or so. It is. It's a good time. Good to be alive. The moon slips through the ecliptic plane, and we see it snuzzling with the planets. Snuzzling?

Snuzzling. Anyway, on to this week in space history. This is the 45th anniversary of Scott Carpenter's Mercury launch, Aurora 7, the final pieces of the Mercury program, 45 years ago. One of the pioneers. Yes, and not a bad singing group either. No. On to random space facts.

That was weak. Just do it better when we get together in person again next week. Don't feel bad. It's okay. Spirit, up there on Mars, Rover, currently exploring an area that has been dubbed Home Plate because of its shape that can be seen from orbit looking kind of like a baseball home plate.

Did you know that many of the features there are being named appropriately for baseball players, in particular from the All-American Girls Professional Baseball League and players managers of the Negro Leagues of Baseball from the first half of the 20th century. I did not know that. And you know what's funny? I met one of those All-American Women's Baseball League, or girls, or whatever they called it, baseball league. Yeah, then they called it girls, which is why I quoted from it.

Right. Just last night. Just last night. Really? I had no idea. I was at an event, and sure enough, they had this woman stand up, and she had been in A League of Our Own. Isn't that amazing? That is amazing, and too bad you didn't have this little tribute.

I could have walked right up and told her, do you know that there's something on Mars that's named after you? Yeah. That might have been the end of the conversation. Security. You better move on here. We're running out of time. Trivia contest.

We asked you how many near-Earth objects have been discovered, and we just wanted this kind of within 100 or so because it is changing nearly on a daily basis. How did we do? People did a great job of researching this. Most of them found the same figure that was as of April 26 of this year, according to the site at JPL. And, in fact, we can even provide that link at our website at planetary.org. Are you ready? Yeah.

Let's see if this matches your figure. 4,681 near-Earth objects, 712 of those asteroids with a diameter of one kilometer or larger, 849 classified as PHA. Potentially hazardous asteroids. Woo! Yeah, that means they're scheduled to come for close flybys of Earth. Now, we did have some people who only gave us that figure, but we wanted all of them, not just the potentially hazardous ones.

So Ben Susser, Ben Susser of Livingston, New Jersey, he got that figure from the JPL site. And, Ben, that was good enough, according to random.org, to get you a Planetary Radio t-shirt. Yay! Hey, and if you'd like to win your Planetary Radio t-shirt, or at least go into the random hopper, answer the following question. We're moving to Earth-observing satellites.

What was the first NASA Earth-observing satellite launched as part of what is dubbed the Afternoon Constellation, or the A-Train? I am completely baffled. All right. We'll find out in a couple of weeks. Go to planetary.org slash radio to find out how to enter. Be sure to get us that entry by May 28, 2 p.m. on Monday, May 28, and we'll make you part of the contest.

How's that for a deal? That's a wonderful deal. I wish I could take it. I wish you could, too. But then again, you know all the answers. Well, I should. Let's put it that way. Someone's got to do it.

Someone does. All right, everybody, go out there, look up in the night sky, think about pretty rocks. Thank you. Good night. Bruce Betts is the director of projects for the Planetary Society, and he joins us every week here for What's Up. Planetary Radio is produced by the Planetary Society in Pasadena, California. Join us next time as we dig up some moon dust in the Lunar Regolith Challenge.

Have a great week, everyone. Thank you.