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Skywatching

In a galaxy far away and long ago

Pulse that created it all

It happened eight billion years ago.

The birth of our planet, the Sun and the other bodies of the Solar System lay some 3.5 billion years in the future. There was a colossal energy release in a distant galaxy. One of the things it caused was a pulse of radio energy of enormous power, but only about a millisecond long. That pulse was radiated into space in all directions, including the one in which, billions of years later, our world would form.

As that pulse of radio energy travelled through intergalactic space, the Solar System was born, and soon after, life appeared on the Earth. The dinosaurs came and went, our ancestors came down out of the trees and gradually developed a high-tech society. They became interested in astronomy and eventually built highly sensitive optical and radio telescopes.

When it arrived at Earth, the pulse, now extremely weak, was detected by the Australian Square Kilometre Array Pathfinder (ASKAP) radio telescope, a development prototype for the Square Kilometre Array, an international project to build the largest radio telescope in the world. Australia is a participant and so is Canada.

These short radio pulses have been known for some years, and have come to be called “fast radio bursts.”

Many have been detected, mainly by the ASKAP radio telescope in the Southern Hemisphere, and in the Northern Hemisphere by the CHIME radio telescope, located at our observatory.

This particular pulse is especially interesting because it is the most intense yet detected, and comes from the farthest away.

To be detectable after travelling eight billion light years, that pulse of radio emission must have been unbelievably strong. Moreover, if it was a mere millisecond in duration, the source could not be larger than the distance it takes light and radio waves to travel in a millisecond, meaning the source has to be smaller than 300 kilometres.

For comparison, the Moon has a diameter of 3,475 km, more than eleven times larger. Yet, that tiny object managed to emit, in that pulse, the total amount of energy produced by the Sun over 30 years. There are three objects that are extremely compact which can generate huge energy releases—black holes, neutron stars and magnetars.

Black holes are the ultimate energy machine—drop stuff in. You get almost total conversion of mass into energy. However, black holes are not good at producing short, sharp pulses of radio energy.

Neutron stars, the collapsed cores of dead stars shrunken down to a few kilometres in diameter, can produce pulses of radio waves, but not strong enough to explain fast radio bursts.

The most popular candidate at the moment is the magnetar. These are neutron stars with exceptionally strong magnetic fields. These are so strong that if we were miraculously transported to the surface of a magnetar, and were not instantly killed by the heat, radiation and enormous gravitational attraction, we would be killed by the magnetic fields disrupting our life processes.

If by some further miracle we could walk on that surface and survive, we would find it easy to walk in the direction of the magnetic fields and almost impossible to walk across them.

One way magnetars produce intense energy releases is through stressing their intense magnetic fields. As magnetars spin, these magnetic fields can get increasingly wound up and distorted, storing enormous amounts of energy, like an unimaginably huge, stretched elastic. Eventually, just as in the case of an over-stretched elastic band, the stresses in the distorted magnetic fields get too much and they snap, releasing pulses of energy strong enough to detect billions of light years away.

That is something to ponder.

•••

• Saturn lies in the south after sunset, with Jupiter shining in the east.

• Venus rises in the early hours.

• The Moon will be new on Nov. 13.

Ken Tapping is an astronomer with the National Research Council's Dominion Radio Astrophysical Observatory near Penticton.

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



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About the Author

Ken Tapping is an astronomer born in the U.K. He has been with the National Research Council since 1975 and moved to the Okanagan in 1990.  

He plays guitar with a couple of local jazz bands and has written weekly astronomy articles since 1992. 

Tapping has a doctorate from the University of Utrecht in The Netherlands.

[email protected]



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The views expressed are strictly those of the author and not necessarily those of Castanet. Castanet does not warrant the contents.

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