Rhythmic radio bursts of unknown origin detected in deep space

18 Jun 2020

Image: © sakkmesterke/Stock.adobe.com

While fast radio bursts have been detected in deep space before, one recently discovered by MIT is the first to produce a cyclical pattern.

Since their first detection in 2007, fast radio bursts (FRBs) have captivated the attention of astronomers and the public alike due to their mysterious origins. Now, a team of astronomers led by MIT has published findings on a new type of FRB that’s even more mysterious.

Writing to Nature, the team said it had picked up a curious, repeating rhythm of FRBs emanating from an unknown source located approximately 500m light years away. Since 2007, more than 100 FRBs have been detected. They typically reveal themselves to be one-off events, flashing briefly for just a moment.

In some cases, FRBs have been observed being emitted from the same source, but appear to show no discernible pattern. Now, this new source, catalogued as FRB 180916.J0158+65, is the first to show a predictable, rhythmic pattern. It begins with a noisy four-day window where FRBs are detected, followed by 12 days of silence.

This 16-day cycle has appeared consistently over a period of 500 days of observations. According to MIT assistant professor of physics Kiyoshi Masui, this is a totally new phenomenon in astrophysics.

“It’s the most definitive pattern we’ve seen from one of these sources. And it’s a big clue that we can use to start hunting down the physics of what’s causing these bright flashes, which nobody really understands,” he said.

So, what is causing this?

The research team posed a number of possible reasons as to why this is happening. One possibility is that the bursts may be coming from a single, compact object, such as a neutron star, that is both spinning and wobbling.

Another possibility is that it involves a binary system, such as a neutron star orbiting another neutron star or a black hole. If the first star emits radio waves and is on an eccentric orbit that brings it close to a second object, the tides between them could cause the first object to deform and burst. After swinging away, this pattern would repeat when the star returns to the same point of orbit.

A third possibility could involve a radio-emitting source that circles a central star. If the star emits a wind, or cloud of gas, then every time the source passes through the cloud, the gas from the cloud could periodically magnify the source’s radio emissions.

Finally, the research team proposed that repeating FRBs may originate from magnetars – a mysterious type of neutron star thought to have an extremely powerful magnetic field.

“People have been working on how to make these magnetars emit FRBs, and this periodicity we’ve observed has since been worked into these models to figure out how this all fits together,” Masui said.

Colm Gorey was a senior journalist with Silicon Republic