Back in 2011 and 2012, astronomers working at an Australian observatory picked up a series of fleeting but powerful radio signals. These signals have never been detected elsewhere, casting doubts on their origin. But now, new observations from the Arecibo Observatory in Puerto Rico suggest they're for real.
Top image: Impression of a blitzar — a hypothetical object that could be the source of the radio bursts. Image: Sky & Telescope/Gregg Dinderman.
Up until this point, the only observatory to detect these signals has been the Parkes radio telescope in New South Wales, Australia. The dozen-or-so bursts that appeared in 2011-12 likely originated from outside the galaxy. In just a few milliseconds, each of the radio bursts released as much energy as the sun emits in 300,000 years.
Astronomers have all kinds of theories as to what may be triggering the bursts, including blitzars — overweight neutron stars that are resisting the urge to turn into a black hole on account of their rapid rotation. Other theories include magnetars, which are neutron stars with super-strong magnetic fields, evaporating black holes, and gamma ray bursts that involve a supernova.
The new observations were made at Arecibo on November 2, 2012, home to the world's largest single-dish radio. The data showed a massive 3-millisecond spike, but unlike radio blasts produced by some pulsars, the burst did not recur.
Writing in National Geographic, Nadia Drake reports on the new discovery:
Called FRB 121102, the burst was very similar to six earlier events that constitute the entire reported population of ultrafast radio bursts – a population that until November 2012 had only been seen by one telescope, in Australia.
But transience is only part of what makes these signals so weird. Their chief peculiarity lies in just how dang far away they seem to be.
Normally, radio waves travel at the speed of light. This means that all the different wavelengths and frequencies of radio waves emitted by the same object – say, a pulsar – should arrive on Earth in one big batch.
But if something is sufficiently far away, that changes. Longer, lower frequency waves traveling through the cosmos have a trickier time getting to Earth. Clouds of ionized interstellar particles – electrons, primarily – form roadblocks that slow and redirect these longer waves, causing them to follow a more sinuous path. As a result, the longer waves arrive just a bit later than their shorter kin – sometimes, the difference is only a fraction of a second.
The resulting "dispersion" delay is what's allowing astronomers to estimate how far the waves are coming from. In this case, it's something billions and billions of light-years away.