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GUY RAZ, host:

Now, while Dennis Wheeler is trying to make a map of the Earth's climate in the 17th and 18th centuries, NASA's building a map of the solar system. It's called the All Sky Map, and this week, the space agency announced a discovery that could shed light on an area at the outer edge of our solar system. It's a border region that protects us from cosmic rays.

Richard Fisher is the director of the Heliophysics Division at NASA, and he's here in the studio with me.

Welcome.

Mr. RICHARD FISHER (Director, Heliophysics Division, National Aeronautics and Space Administration): Well, thanks.

RAZ: Some exciting news out of NASA this week. The All Sky Map was unveiled. What is it?

Mr. FISHER: Well, the All Sky Map is the output of something called the Interstellar Boundary Explorer Mission. And this is an experiment that was designed to make a picture of the boundary between our galaxy and our Solar System. And the reason there is such a thing is, if you can imagine the circumstance, where we have a solar wind, and what that means is it's a wind off our star - and if you have wanted to try and visualize this, think about standing here on Earth and you had a wind that blew straight up off the planet - and the sun blows a great, big bubble around our solar system, and it's a protective bubble. It convects magnetic field out to the edge of this, and it produces a magnetic shield around our solar system.

RAZ: That shield is the heliosphere.

Mr. FISHER: That shield is the heliosphere.

RAZ: And it protects us from?

Mr. FISHER: From cosmic radiation from the galaxy. It absorbs about 68, 75 percent of all the galactic, cosmic radiation, and we're shielded from the rest of it by the Earth's magnetic field. So here on Earth, we're pretty safe from this stuff.

RAZ: So in 2008, NASA launched the IBEX, the Interstellar Boundary Explorer, the spacecraft that takes photographs way out. What did it capture?

Mr. FISHER: Well, it captures an image that looks like what it would be if you were inside of a bubble, if you can imagine such a thing, and you would have to look around. You'd have to turn your head every direction in order to see all the features. And so we have a way of plotting this on a single map, and it's kind of an oval map; it's a projection. And what it shows is that there is a stripe across the inside of this bubble.

The question is: what is that stripe? It's completely unexpected. What I had anticipated, and I'm kind of a traditional physicist, what I'd expected would be that we'd see it bright on one side and dark on the other because material was piling up on the side that's plowing through the galaxy, and that is visualized to a certain extent, but this other feature is - has another characteristic which is very curious, which is aligned, and it's perpendicular to what we think is the direction of the magnetic field of the galaxy.

RAZ: Well, what does it tell us about our place in the galaxy?

Mr. FISHER: Well, I think that what it tells us is that first of all, there's a little bit of come down to Earth and be a little bit humble because all of a sudden, expectation doesn't fit preconceived theory.

RAZ: But what was the expectation?

Mr. FISHER: The expectation was there would be a teardrop-shaped structure, sort of a bubble plowing into the galactic wind on one side and trailing off sort of like a teardrop on the other side.

RAZ: Is it the farthest out we've ever seen?

Mr. FISHER: Oh, no. We see much further out than this, but it's the first time we've seen this structure. There's been no way to visualize it previously. It isn't actually light. It's - we're detecting particles that come from that region. So it's as if you had a bank of cloud that was emitting some kind of particle, like a raindrop, only in this case, it's emitting neutral hydrogen. And so the neutral hydrogen detectors make this image for us.

RAZ: So we don't actually know what this stripe does?

Mr. FISHER: Well, we know it's made out of hydrogen, out of protons that recombine with electrons. We don't know the process by which it is draped over the heliosphere, and we also don't understand exactly why it has brighter spots in it. It's not just a uniform kind of stripe. It's got intensity and density in it. And what in the world makes that? That's - it's going to be fascinating to see.

RAZ: Where do you go from here? I mean, how can you continue or how will you continue to study this stripe in the heliosphere?

Mr. FISHER: if there are changes in it, we certainly know that the changes can come from either changes in the galactic wind blowing on us or changes in the solar wind that blows this bubble. And we can follow the solar wind pretty well, and we'll straighten out causality. What are these changes, and why are they there?

I think the second thing is that it just says in previous models, we're not using the right physics, and the physicists are going to have to go back and consider what physical processes may be left out of these calculations. And my guess is that within a couple years, we'll have a pretty good explanation of this.

RAZ: Richard Fisher is the director of the Heliophysics Division at NASA.

Thanks so much for coming in.

Mr. FISHER: Oh, thank you so much. It's a great pleasure to be here.

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