Mysterious Radio Bursts Have Astronomers Scratching Their Chins


Animation illustrating the random appearance of Fast Radio Bursts on the sky. Credit: NRAO Outreach/T. Jarrett (IPAC/Caltech); B. Saxton, NRAO/AUI/NSF

From the mountains of British Columbia comes news of powerful bursts of radio energy from deep space. Astronomers estimate that thousands of these enigmatic lights scintillate across the sky, but they’re so fast and random it’s hard to know where to point a telescope to capture one. Called fast radio bursts or FRBs, they last only a millisecond or two, about as long the light in a typical photo flash. If our eyes could detect radio waves, the sky would pop like cameras at a presidential press conference.

The CHIME array is made up of four 100-meter-long half-cylinders shaped like snowboarding half-pipes. It has a wide field of view perfect for detecting FRBs. The array will also be used to study the expansion of the universe to shed more light on the nature of dark energy. Dark energy, whatever it might be, is behind the accelerating universal expansion. McGill University

FRBs aren’t new. Astronomers found the first one in 2007. Only a few dozen bursts had been discovered until the new Canadian Hydrogen Intensity Mapping Experiment (CHIME) instrument started looking last summer. Since then, the CHIME array of radio telescopes has already spotted 13 new bursts including one that’s burst multiple times called a “repeater.” Only two repeaters are known. The telescope’s large collecting area and enormous field of view make it the ideal FRB detector. Once it’s fully up and running, CHIME is expected to spot between 20 and 50 bursts a day.

This photo shows the distant host galaxy of fast repeating radio burst FRB 121102. The remote galaxy is located in the winter constellation of Auriga. Although we don’t know exactly what causes them yet, the bursts do appear to originate in distant galaxies. Gemini Observatory NRAO/AURA/NSF/NRC

So what are these flashes of light that are so brief yet manage to pack 500 million times the energy of the sun? Nobody knows, but that hasn’t stopped scientists from proposing explanations. To date, there are at least 45 published theories on the subject. The first repeater, FRB 121102, discovered in 2012, has erupted more than 200 times, allowing astronomers to trace its origin to a star-forming region in a dwarf galaxy 3.2 billion light years away.

Some astronomers think it might be a flare from a recently formed neutron star, a tiny, city-sized stellar ember with 2-3 times the mass of the sun born in the aftermath of a supernova explosion. The radio signal from the object also appears twisted as if it had passed through a powerful magnetic field, something that’s common to an even rarer type of neutron star called a magnetar. A Magnetar is a fast-spinning, highly magnetic neutron star that releases energy as its field decays and weakens. Hypothetical starquakes could also be at play caused by shifts and adjustments in a neutron star’s superdense crust.

The briefest FRB burst detected so far lasted just 30 microseconds, which means it had to come from a very small source about 6 miles (10 km) across — again, just about right size for a neutron star.


The new CHIME telescope will go deep and wide

All 13 of the new detections including the second repeater come from a region of space 1.5 billion light years away. Because of the way their light is scattered, they appear to be located in extreme environments filled with hot, turbulent, electrically-charged gas inside their home galaxies.  FRBs also may be linked to black holes. One theory involves matter that gets shot out of a black hole, collides with a cloud of molecules and excites them to give off a brief but intense flash of radio light.

This artist’s impression of a magnetar, a neutron star with an extremely powerful magnetic field. ESO / L. Calcada

Hopefully we’ll get a better handle on what these flickering lights are as the data pours in from CHIME. At the same, they’ll also be using these cosmic flashbulbs to probe the vast spaces between the galaxies. Light from the sources is imprinted with information about the matter it passes through on the long journey to Earth. In such diverse and inventive ways, we learn more about what lurks in deep space.

5 Responses

  1. Rajesh

    Is there a way to generate these in laboratories at scale? May be that should shed some light whether these are ET or naturally occurring?

    1. astrobob

      Rajesh,

      Since we don’t know what they are, we can’t generate them. But the energy involved would be impossible to reproduce in a lab. They are almost certainly naturally occurring because they’re all over the sky and associated with high-energy environments like neutron stars and black holes.

Comments are closed.