Mystery Signals from Space

Four powerful radio bursts have left astronomers puzzled.

If you’ve been waiting for mysterious radio signals from space, tune in. An international team of astronomers has detected four powerful bursts that appear to come from billions of light-years away. At that distance, the radio pulses would each have put out in a few thousandths of a second the same amount of energy that the Sun would need 10,000 years to emit.

(So no, it’s not E.T.)

The bizarre signals came to light as part of the High Time Resolution Universe survey, a project using the 64-meter Parkes radio telescope in Australia to search the sky for radio blips and pulsars, the spinning-lighthouse-like stellar corpses left behind by some supernovae. Because the pulsars we detect lie in our own galaxy, astronomers mostly look near the Milky Way’s plane when hunting for these zombie stars. But when grad student Dan Thornton (University of Manchester, U.K., and CSIRO, Australia) started digging through normally “boring” data far from the galaxy’s dusty gleam, he stumbled across the four enigmatic bursts.

The fast radio bursts (or FRBs) have a distinct look to them. They’re incredibly energetic and über-short, but their lower frequencies arrive noticeably later than their higher ones, spreading out the signal into a unique shape. This spreading happens because the lower radio frequencies interact more with intervening electrons, either in the Milky Way itself or the so-called intergalactic medium, the stuff between the universe’s massive stellar metropolises.

The pulse shape encodes how much stuff lies between us and a source, and the spread in these narrow signals’ arrival times implies that they came from far beyond the Milky Way. Throwing some assumptions into the mix, Thornton and his colleagues estimate the four bursts originated at redshifts from 0.45 to 0.96, or 5.5 to 10 billion light-years away.

That distance would give the bursts energies between 1037 and 1039 joules, or between 100 billion and 10 trillion times the energy the Sun puts out in a single second — and the FRBs did it in a few milliseconds.

These four bursts aren’t the first to baffle astronomers. In 2007 Duncan Lorimer (now at West Virginia University) and his colleagues reported a bizarre radio blast so strong that the software used to process the signals assumed it couldn’t be astrophysical and deleted part of it from the data. That “Lorimer burst” looks like the new four.

There was also a weird signal reported in 2012, but it’s unclear whether it came from the Milky Way or not. Plus, notes Bryan Gaensler (University of Sydney), a team reported a bunch of unidentified radio bursts back in 1989 that might or might not be similar. “No one knew what to make of that paper at the time, but now it’s somewhat more interesting,” he says.

So what are FRBs? “I don’t think we have any idea what these are,” Gaensler says. “It’s a mystery!” […]

Full Article

Reference: D. Thornton et al. “A Population of Fast Radio Bursts at Cosmological Distances.” Science, 5 July 2013.

Credit: Camille Carlisle/skyandtelescope.com


Posted 9 months ago with 1,225 notes
Tagged:astronomyspacescienceParkes radio telescopeMilky Way GalaxypulseFRBstars

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