What makes the MWA, the MWA.

Radio Astronomy

When you think of astronomy, you might picture someone peering through the eyepiece of a small optical telescope. This is the way that astronomy has been done for centuries, but as our understanding of the Universe has evolved, and new technologies have emerged, we’ve discovered more ways to look at the sky. This is because the light that we see with our eyes, optical light, is just one small part of the greater electromagnetic spectrum. There are many different kinds of light, including x-rays, gamma rays, infrared, and radio. Many stars and objects in the Universe give off radio light, which we can see with our radio telescope, the MWA.

Explore the electromagnetic spectrum with GLEAMoscope below, and at this interactive page:

A bit of background...

Radio astronomy was pioneered in the 1930s, with engineers and physicists such as Karl Jansky and Grote Reber who measured the first radio signals from space.

Since then, many breakthroughs have been made in the field by astronomers seeing the Universe in a whole new light, such as the study of the Sun’s radio emissions by Ruby Payne-Scott in 1945, and the discovery of pulsars in 1967 by Jocelyn Bell Burnell.

Joseph Pawsey introduced interferometry to radio astronomy, and is attributed with the growth of the field in Australia, where it has since become one of the country’s scientific strengths. The Pawsey Supercomputing Research Centre, which houses the MWA data archive, was named after him.

Two of Grote Reber’s radio maps (1938).
Why do we do radio astronomy?

You might wonder why we bother with radio astronomy at all! It is very useful because it often tells us new information. For example, the images below are of the same galaxy, Centaurus A, but the first picture was taken by an optical telescope, and the picture below was taken by a radio telescope – the MWA!

Centaurus A, also known as NGC 5128, at optical wavelengths. Credit: ESO
Centaurus A, imaged at radio wavelengths with the MWA telescope. Credit: Ben McKinley, ICRAR/Curtin and Connor Matherne, Louisiana State University

Instead of all the dust in the disk of the galaxy, the radio image reveals huge jets of material that are being ejected from the supermassive black hole in the galaxy’s centre. We would never have known these jets existed if we continued to look at Centaurus A with only our eyes. For this reason, astronomers who are researching the nature of objects will often use multiple telescopes that see in different parts of the electromagnetic spectrum.

Radio light has a longer wavelength and can travel further without being hindered by dust and gas, meaning we can peer further into the history of the Universe than ever before with instruments like the MWA.

Why do we use antennas instead of a dish?

The MWA radio telescope is made up of thousands of antennas, all sitting out in the Murchison, like one big ear listening to the sky. Once we process the data from all the antennas, we can make images to view the sky at radio frequencies.

Traditionally, radio telescopes look like a big version of a satellite dish, which provide excellent sky coverage (such as the Parkes observatory!). If you’d like to increase your instrument’s performance even more, there are some physical limitations to how large you can make your dish.

Our work-around to this problem is using a technique called interferometry. Having many small antennas spread over the outback and working together brings us close to the equivalent of one massive antenna that is kilometres wide, which would otherwise be logistically impossible!

Many of the antenna tiles in the MWA’s “southern hexagon”. Credit: ICRAR/Curtin
Why are the antennas spread out in patterns?

It’s not just the number of antennas that affects what you can see with your radio telescope, but also the way you arrange your antennas. This is why the MWA has different patterns, or configurations, of its antennas.

In short: having antennas close together, such as in our compact configuration, makes it easier for astronomers to view large-scale or diffuse structures, such as the EoR. Conversely, having antennas far apart from each other in our extended configuration increases the telescope’s ability to resolve small scale structures with more detail, such as galaxies.

The MWA can operate in either ‘compact’ or ‘extended’ configuration, offering the best of both worlds (deep surveys and detailed imaging).

MWA antenna tiles in compact configuration (blue) or extended configuration (orange), by distance from the centre of the array. Credit: Wayth

More technical information can be found on the wiki, here:

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Findings worth tuning into

MWA astronomers are leading the way at low frequencies – read up on the latest news.