Radio Bursts Traced to Faraway Galaxy, but Caller Is Probably ‘Ordinary Physics’
By DENNIS OVERBYE
Jan 4 2017
Astronomers have traced a series of brief, enigmatic bursts of radio waves to a galaxy far, far away and indeed a long time ago — some three billion years or so.
But as much as you might be hoping or dreading it to be true, this is probably not E.T.
“We’ve joked about spaceship battles and death stars blowing up, but we think we can explain it with ordinary physics,” said Shami Chatterjee, a Cornell astronomer.
Dr. Chatterjee is the lead author of a paper published in Nature on Wednesday that details the search for the source of the radio waves known as “fast radio bursts,” intense pulses of radiation from the sky lasting only a few milliseconds. He also spoke at a news conference sponsored by the American Astronomical Society in Grapevine, Tex.
These have been disappointing times for those yearning for some alien direction from Out There. Last summer, Russian astronomers reported that they had recorded a promising-sounding signal from a star in the Hercules constellation, but they dismissed it when it became public as a freak bit of random radio noise, the astrophysical equivalent of a cosmic butt dial.
More recently, searches for radio signals from a set of stars with anomalous spectral features and another star known as Tabby’s Star that has shown suspicious variations in its light seem to have come up empty.
So at least for now, the skies appear to be bereft of intelligence. But the new results from the fast radio burster, known as 121102 — after Nov. 2, 2012, the date it was first observed — need not discourage any aficionados of cosmic mystery.
Most likely, Dr. Chatterjee said in a telephone interview, the bursts could be caused by weird reactions between a neutron star — the dense spinning magnet left behind by a supernova explosion — and the debris from that explosion. Or perhaps from some unexpected quirk of a supermassive black hole in the center of the galaxy, a dwarf assemblage of stars some three billion light-years away in the constellation Auriga.
There are problems with both explanations, however, he added.
Fast radio bursts have led astronomers on a merry chase ever since they were discovered in 2007 in data recorded earlier by the Parkes radio telescope in Australia.
Because they are so short and until recently have never been seen to repeat, these phantoms have been hard for astronomers to study. Usually, astronomers notice them after the fact. Moreover, radio telescopes have poor angular resolution, making it impossible to determine exactly what star or distant galaxy they came from.
The radio emissions themselves, Dr. Chatterjee said, resemble the blasts from pulsars — the spinning neutron stars that emit clocklike pulses of radiation and whose discovery in 1968 did indeed elicit speculation about little green men. But the radio waves arrive on Earth dispersed or spread out in time by wavelength, which implies that they have traveled from far outside our galaxy.