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Skywatching

A way to 'see' into space

For the last few years, a group of nations, including Canada, has been working on what will be the largest radio telescope in the world. The project involves the development of new technologies and techniques, and the reward will be an unprecedented scientific research tool.

Radio astronomy was born in the 1930s. However, the dramatic advances in radio, radar and electronics in the Second World War set the stage for the explosive growth of radio astronomy over the following 20-30 years. Now we are reaching a limit. Since WWII the sensitivity of the receiving systems used on radio telescopes has increased by a factor of a thousand or more. However, we are now at a point where pushing radio technology further might double the sensitivity, but not much more than that.

When an astronomical object radiates light, radio waves or any other electromagnetic wave, the energy spreads out as it travels into space. This effect, known as the inverse square law, says that if we increase the distance by, say, a factor of ten, the strength of the waves decreases by a factor of 10-squared, 10 x10, 100. To probe out further into space, back towards the beginning of the universe, we need a radio telescope about 100 times the sensitivity of anything available now. We know there is no way we can achieve this by making more sensitive radio receivers. Fortunately, there is another, practicable solution.

The amount of signal power we receive depends on the size of the antenna. The bigger it is, the more signal power we collect. We can therefore achieve a hundred-fold increase in sensitivity with current receiver technology by building an antenna system with 100 times more signal collecting area than any radio telescope antenna currently in use. We need an antenna with a collecting area of a square kilometre, a million square metres. There is no way we can build an antenna that big.

However, we can make lots of little antennas in a great enough number for their combined collecting area to be a square kilometre. Because smaller dishes "see" a bigger patch of sky than big dishes, the vision we have for the Square Kilometre Array consists of thousands of little dishes. This could be hugely expensive, so we are doing an advanced engineering project at our observatory to develop accurate, small dishes using the relatively cheap carbon-fibre composite material used to make boats.

This work was highly successful and has led to enquiries from around the world regarding the application of this technology to other antenna projects. Collecting and combining the signals from thousands of antennas acting together as one huge antenna requires a huge number cruncher. NRC engineers are working on this.

The ability to map detail increases as the array of antennas gets bigger. If we are using thousands of little dishes, we don't have to cram them together in a single, compact group. We can spread them out The plan is to put part of the instrument in South Africa and the other part in Western Australia. It would be nice to build the array in Canada, but we are too far north.

The most interesting parts of our galaxy, the Milky Way, are visible at locations in the Southern Hemisphere, not too far south of the Equator. Considering the size of this project it is a good idea to put the instrument in the best place.

Projects like this have additional value in that they drive the development of exciting new technologies in an open and public manner. This makes them a powerful incentive for students in the participating countries to choose science and engineering as careers. The expertise needed to develop major scientific instruments is applicable to many other aspects of our lives.

  • Jupiter and Saturn rise before midnight. Jupiter is the bright one.
  • Mercury lies low in the dawn glow.
  • The moon will reach first quarter on the 17th.


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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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