The night sky looks calm, but if you listen in on the radio band, it's full of short clicks and rustles. Astronomers are combing the sky for solitary radio pulses — bursts lasting milliseconds that come from various corners of the Galaxy and beyond.
One such search is underway at the 100-meter radio telescope in Effelsberg, Germany. The High Time Resolution Universe survey has already covered about 21% of the northern sky. And here's the first major find: a fast radio burst FRB20110220A. This is a powerful pulse that lasted only 11.9 milliseconds, yet in that time it delivered as much energy as the Sun radiates in several days. It was caught when the signal passed through clouds of interstellar gas, and from the delay of the signal at different frequencies, the distance was calculated — about 1.6 billion light-years.
In addition, the telescope for the first time spotted a rotating radio transient J2028+28 in the L-band (around 1.4 GHz). This is a neutron star that doesn't shine steadily like a normal pulsar but flares up from time to time. Its position was refined and its rotation period estimated. Another new transient, J0404+53, was previously thought to be a single pulse, but is now confirmed as a repeating source.
This skew toward the galactic plane is an important clue. Faint single pulses most likely originate in our Galaxy, not from deep space. They could be young neutron stars that haven't spun up to become stable pulsars, or magnetars — stars with extremely strong magnetic fields.
The search continues. Each new burst is like a click in the silence, helping to map the invisible radio sky. And the more such clicks we hear, the clearer it becomes who is making them.
The fast radio burst FRB20110220A lasted only 12 milliseconds—80 times shorter than a blink of an eye, but in that time it released energy comparable to several days of the Sun's shine.