Rare radio bursts have extragalactic origin

Mysterious signals come from a galaxy 3 billion light-years away.

5th January 2017
Rare radio bursts have extragalactic origin © Getty/Richard Maschmeyer/robertharding

Astronomers have pinpointed a distant galaxy responsible for fast radio bursts, after tracking the mysterious phenomena with a telescope array for the first time.

Fast radio bursts (FRBs) are high-energy pulses of electromagnetic radiation that last for only 1-5 milliseconds – just 18 have ever been detected. The fact that they are so uncommon has led astronomers to suspect they must originate from very powerful events outside of our Milky Way galaxy.

The new study, published in Nature, narrows the list of celestial suspects by localising the bursts to an optically faint dwarf galaxy around 3 billion light-years from Earth. “Finding the host galaxy and its distance is a big step forward”, says team leader Shami Chatterjee of Cornell University.

The Very Large Array (VLA) of telescopes in New Mexico was the first to lock onto the dwarf galaxy. The VLA later discovered that the galaxy continuously emits low-level radio waves as well, suggesting it orbits around a central supermassive black hole.

"We think the bursts and the continuous source are either the same object, or are somehow physically associated with each other," says Benito Marcote, whose team used a European telescope array to confirm and refine the VLA data.

Two possible sources of the FRBs are a black hole or a highly-magnetic form of neutron star called a magnetar, both the products of exploding stars called supernovae. As young magnetars mature, they slow their rotation and can emit periodic radio pulses, while black holes produce radio emissions by acting on the material surrounding them.

The bursts in this study are unique in that they repeated, after first being detected in 2012 by a single-dish radio telescope and named FRB 121102.

"For a long time we came up empty, then got a string of bursts that gave us exactly what we needed," says Casey Law of UC Berkeley, who also worked on the study.

This repetition offered the perfect opportunity to ambush the signal with an array – allowing the precise location and distance of the source to be determined.

The team’s next step will be to improve their computer processing power in order to detect and analyse FRB sources in real-time, hopefully letting them determine exactly what is producing them, as well as where.