Pulse of the universe

Long ago, in a galaxy 3.6 billion light years away, something strange happened.

Whatever it was produced a short pulse of radio waves about a thousandth of a second long. The energy was comparable with the total energy produced by the Sun in a century.

To produce such a short pulse, the source cannot be larger than a thousandth of a light second in size, around 300 kilometres at most.

We can think of a few phenomena that can produce such a high-energy pulse. Our ideas include a black hole, colliding neutron stars, or the energy released by tangled magnetic fields in a magnetar, the highly magnetized core of an exploded giant star.

At that time, 3.6 billion years ago, the Earth was about 1.5 billion years old. Primitive life, such as stromatolites, inhabited the young world's oceans. The atmosphere was not yet breathable. However, algae in the oceans were busy photosynthesizing oxygen. 

About 100,000 years after it was produced, the pulse left its galaxy, radiating out in all directions into intergalactic space.

The material in space is more rarefied than any vacuum we can achieve in the laboratory; however, there are still a few atoms, free electrons and very weak magnetic fields.

These affect the radio waves, in near-empty space, the effect is slight, but over billions of light years it builds up into something significant.

When it was produced, the pulse spanned a wide range of radio frequencies; a radio tuned to it would have received a sharp click and radios at different frequencies would have received the signal at exactly the same time.

However, gradually, as it travelled through intergalactic space, the electrons present oscillated with the pulse and reradiated it. The result was a delay, which was smallest at the high frequencies and highest at low frequencies.

The click became a descending tone, where radios tuned to high frequencies would pick up the pulse before radios at lower frequencies would.

This process, known as dispersion, allows us to estimate how far the pulse has travelled. This is important in helping us identify the source and the energies involved in the process that produced it.

About 100,000 years ago, when Neanderthals were the dominant species of human and Cro Magnon man, our species, was still about 50,000 years in the future, the pulse entered our galaxy, the Milky Way.

About 3,000 years ago, when the Egyptian empire held sway in the Middle East, the pulse entered our neighbourhood, the zone containing the familiar stars in our night sky.

When Karl Jansky discovered cosmic radio waves and started the science of radio astronomy in 1932, the pulse was about 88 light years away.

Finally, when it arrived at the Earth, after travelling for 3.6 billion years, it so happened that the side of the Earth facing the incoming pulse had radio telescopes searching for such pulses.

The pulse signal was collected by the antennas, magnified by very sensitive amplifiers and digitized. Then, sophisticated software, searching the incoming signal for these dispersed pulses from far off, flagged the signal and sent a message to a computer terminal.

The observer saw it, turned to her companion and said: "I think we've detected another Fast Radio Burst.”

The advent of radio telescopes such as the CHIME radio telescope, operating at the Dominion Radio Astrophysical Observatory, is ideally suited for detecting these fast radio bursts, or FRBs, because it can see a large area of sky at the same time. It turns out that FRBs are common, with many occurring a day.

We would really like to know what sort of bizarre physics is making them.

• After dark, Saturn and brilliant Jupiter lie low in the south
• Mars rising in the east.
• Venus, which is even brighter, rises in the early hours.
• The Moon will reach Last Quarter on Oct 9.

This article is written by or on behalf of an outsourced columnist and does not necessarily reflect the views of Castanet.