The search for mysterious “fast radio bursts” – very brief but intense pulses of radio waves from outer space – is heating up. Nobody knows what causes these powerful bursts, but some have even speculated that the signals could be transmitted by distant alien civilisations. In fact, astronomers are so perplexed by the phenomenon that it is driving a renaissance in radio astronomy.

Now an international team of astronomers has detected the brightest ever fast radio burst. Dubbed FRB 150807 after its discovery date, the burst of intense radio waves lasted less than half a millisecond – that is 0.1% of the time it takes a human to blink. And the study, published in Science, has come closer than any before it to pinning down where the blip came from. The research comes just days after another study reported having seen a fast radio burst together with an outburst of gamma rays, extremely energetic electromagnetic radiation.

Despite their intensity, the nature and origin of fast radio bursts is still hotly debated. Some astronomers have suggested these brief, intense flashes are flares produced in the atmospheres of certain stars in our own Milky Way galaxy – a process similar to solar flares. Others argue they are caused by cosmic collisions such as a neutron star (a collapsed core of a large star) colliding with a black hole in a distant galaxy, or speculated that they could be alien signals.

NASA's Goddard Space Flight Center/S. Wiessinger

The first fast radio burst – the Lorimer burst – was discovered serendipitously by radio astronomers using Australia’s Parkes telescope to search for pulsed radio emissions from spinning neutron stars called pulsars. The Lorimer burst remained a curiosity until other fast radio bursts at different positions in the sky were discovered by other telescopes such as the giant Arecibo radio telescope in Puerto Rico and the 100-metre Greenbank dish in the US.

But progress in understanding this enigmatic phenomenon has been slow. This is partly down to the short duration of the bursts, the limited resolution provided by the telescopes and the uncertainty of the sky positions of the bursts. Trying to discover a burst and, at exactly the same time, pinpoint accurately where in the sky it comes from is difficult. If a radio signal could be backed up by telescopes that are searching for other kinds of electromagnetic radiation (such as X-rays or the kind of “optical light” that we can see), we could measure the distance and understand the physics processes driving these events. If the processes driving these bursts are similar to those responsible for other cosmic explosions, such as gamma ray bursts, astronomers suspect that radiation at other wavelengths is likely to be emitted in the same event that caused the fast radio bursts. But it’s proven difficult to catch.

Indirect estimates of distances have been made by measuring how the radio signal is smeared out. This can help infer the amount of material the light has travelled through. From this, the distance of the fast radio burst from Earth can be estimated, using a variety of assumptions such as the amount of matter between us. Such measurements have indicated that the origins of fast radio bursts lie far beyond our galaxy.