Mysterious Radio Bursts, Sent From Deep Space

Reporting in Science, researchers write of discovering four radio bursts from outer space. Physicist Duncan Lorimer, who detected the first such explosion in 2007, discusses what could be causing these radio signals, such as evaporating black holes, an idea proposed by Stephen Hawking in the 1970s.

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IRA FLATOW, HOST:

Up next, another edition of the ever-popular We Have No Idea What's Going On Here. Six years ago, my next guest announced a strange discovery. He detected a signal from outer space, a burst of radio emissions, just milliseconds long, from outside our galaxy. It was the first of its kind. No one could figure out what might have caused it, either.

And now we know it wasn't a fluke. Last week, astronomers added four more of these mysterious radio bursts to the list. They tracked them from coming in from all over the universe. The furthest one was 11 billion light-years away. Their findings appear in the journal Science.

But what's causing them? Is it a signal from intelligent life? Should we call back Jill Tarter and the SETI Institute? Or is there more a plausible, but eye-opening explanation like a black hole evaporating? Mm. Duncan Lorimer is the Woodburn professor of physics at West Virginia University in Morgantown, West Virginia. Welcome to SCIENCE FRIDAY.

DUNCAN LORIMER: Good afternoon.

FLATOW: These are very mysterious bursts, and you have no idea what they are.

LORIMER: That's about the top and bottom of it, yes. Yeah, we really - just beginning to come to terms with what they are and what they could be.

FLATOW: Mm-hmm. You discovered the first one of these. They're called the Lorimer bursts, named after you. Did you know that it was going to be so tough to figure it out?

LORIMER: Yes. I think right from the beginning, we were really scratching our heads. The first person to see this was actually my undergraduate student David Narkevic, who was working for me at the time. And when he - I can still remember when he brought it into my office and showed me this plot. We were looking at the data for something else, and we came across this signal. And, yeah, we...

(LAUGHTER)

FLATOW: Did...

LORIMER: We've been losing sleep about it ever since.

FLATOW: Did you think it was a fluke or something?

LORIMER: We were - right from the get-go, we were convinced that it was astrophysically real, because of the properties that we saw in the data. It sweeps across the band, just like we would expect, and like we see in other astrophysical sources. But, yes, because it was only one source, you know, normally scientists and astronomers like lots of sources. A sample of one is always rather uncomfortable.

FLATOW: Yeah. I'm reminded of the discovery of the cosmic background radiation over at Bell Labs back, what was it, in the '50s, and they couldn't figure out what the heck - they thought the instruments were bad.

LORIMER: Right. They thought, at one point, pigeons have - had been getting into the detectors.

(LAUGHTER)

FLATOW: OK. So you've had time to think about it. Can you speculate, then, what these bursts may be?

LORIMER: Yes. It's always fun to speculate. I think we're in an era right now where they're probably going to be more theories than bursts for quite a while. So, you know, you mentioned in your introduction the possibility of extraterrestrial intelligence sending this signal. I think that becomes unlikely now that there's more than one of them. With one source, you could always think about it as some sort of single civilization. But now, you're seeing them, essentially, at different parts of the sky. It's very unlikely that different civilizations would be sending things in exactly the same way.

So I think it's something natural in origin, and that - it's really the time scale is the biggest clue to the size of the object, because it's only a few milliseconds in size. The emitting region can only be a few light-milliseconds across. And so that points to some sort of compact, star like a black hole or a neutron star where, potentially, there's large amounts of energy can be released.

One very interesting paper that came out last week was that it's - it could be electromagnetic energy from a collapsing neutron star, collapsing to a black hole, and energy was released as the star collapsed.

FLATOW: All right. Stay with us, Dr. Lorimer. We're going to take a break. When we come back, we'll talk a lot - lots more about this strange burst coming from outer space. Stay with us. We'll be right back after this break.

(SOUNDBITE OF MUSIC)

FLATOW: This is SCIENCE FRIDAY. I'm Ira Flatow, talking with Duncan Lorimer about the Lorimer bursts, named after him, discovered eight years ago. New bursts discovered of some mysterious energy coming from somewhere in the galaxies. And there's no doubt that you will discover what it is someday, is there?

LORIMER: I think it's fair to say that we'll get to the bottom of it. The story of these bursts closely parallels what happened with gamma-ray bursts about 40 years ago, where people discovered these things and, initially, were very puzzled. But, eventually, it took collaborations - large groups of astronomers to find counterparts of the signal, other parts of the electromagnetic spectrum. And that's what's - one of the things that people are trying to do here. They can locate a galaxy where - that's hosting one of these sources, and you can pin down a distance, and you start to really understand the energetics and really go forward from there.

FLATOW: But in the meantime, you have this giant source of energy sending a beam toward you. Can you use that beam going through space to study what's going on in that space?

LORIMER: Yes. That's one of the very exciting side benefits of these sources. The signals propagate through intergalactic space. You know, we're fairly convinced that they are - they're coming from well beyond the Milky Way, and there's a lot of interest in probing the space between galaxies. We're quite aware of studies of dark matter based on galaxy dynamics and other measurements, so matter that you can't see, that's gravitationally attractive.

Here, we're able to potentially look at the - what's known as baryonic matter, normal matter - in this case, the free electrons that are propagating the intergalactic space. So if we can measure one of these host galaxies, we can literally count the number of free electrons along the line of sight to one of these bursts. And that gives us a brand-new probe of the electron content of the universe, which is really exciting.

FLATOW: Mm-hmm. Do you think these are very rare events, or might they be happening all the time, and you just discovered them?

LORIMER: Well, the radio telescopes that found them have very small fields of view, and the bursts themselves don't last very long. And it's becoming clear from these recent results that the bursts could be going off in - over the entire sky about once every 10 seconds.

FLATOW: Wow. Wow.

LORIMER: So that's quite high when you compare it to supernovae, extragalactic supernovae, gamma-ray bursts. So it's quite a puzzle as to what's producing these events so often.

FLATOW: Might you have to come up with a whole different object there that's making these, that you've never seen before or thought about?

LORIMER: Possibly. This scenario that I outlined before the break about these collapsing neutron stars, the people that came up with that are dubbing those blitzars.

FLATOW: Blitzars?

(LAUGHTER)

LORIMER: Just like an explosion. They get it from the German for thunder and lightening. So, yeah, that's using a nice, fancy word, but it's using a phenomenon that we think we understand, and that is these neutron stars. So, you know, things like that are possible. But, yes, I mean, people are free to postulate more exotic phenomena. And, you know, I think the jury's very much open.

FLATOW: All right. Sounds quite interesting. Thank you very much for taking time to talk with us. Good luck to you.

LORIMER: Oh, you're very welcome. Thank you.

FLATOW: You're welcome. Duncan Lorimer is the Woodburn professor of physics at West Virginia University in Morgantown, West Virginia.

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