Astronomy Cast Full Raw Feed · Fraser Cain & Dr. Pamela L. Gay

Ep. 748: Fast Radio Bursts

·55 min·5 clips

One fast radio burst repeats every 16.35 days, hinting at orbital motion around a mysterious object.

The raw feed starts crooked in a very human way. Tornado weather knocks out power, a computer has to reboot, software updates interrupt things, audio gets muted, and a chair briefly looks like a ghost. Once the science gets moving, the question is sharp. Fast radio bursts last such a short time that the source has to be tiny, and that timing clue does real work. Neutron stars land on the suspect list pretty quickly. The host brings up a 2004 magnetar event on the far side of the Milky Way's core, where a magnetic-field rearrangement released a huge gamma-ray burst and saturated space-telescope detectors. That is a useful clue, but not a neat answer. Magnetars can throw short, enormous bursts of energy across the electromagnetic spectrum, so they are hard to ignore. The awkward part is that these bursts do not show up with matching gamma rays. Most have only been caught once: one flash here, silence, another flash somewhere else. That gives astronomers scattered incidents instead of a clock they can watch. Repeaters help. They point back to the same place more than once, even when their pattern refuses to behave. Then FRB 1809-16 makes things stranger. It is in a star-forming region of a spiral galaxy and repeats every 16.35 days, plus or minus 0.15. Orbital motion becomes the tempting guess, but the host keeps the maybe where it belongs. The case keeps getting narrower without getting solved: tiny source, millisecond flare, possible neutron-star physics, missing gamma-ray partners, sources beyond the solar system, some at cosmological distances, and one oddly regular repeater. The chatter and glitches keep it loose, like two science friends hauling the messy process into view.

As heard by us

A brisk tour of one of astronomy's brightest and least settled mysteries.

Fast radio bursts make for a clean kind of mystery: brief, powerful flashes that still do not fit neatly into one explanation. The episode handles that well, moving through the scale problem, magnetars, repeaters, and the 16.35-day object without pretending the case is closed.

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