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In much the same way that you tune your radio to listen to your favourite music, radio astronomers can tune their telescopes to pick up the radio waves that come from quasars, other distant galaxies
and the cosmic microwave background that are millions of light years from
the Earth.
Telescope at the Hartebeesthoek Radio Astronomy Observatory. Credit: Thomas Abbott |
Very Large Array (VLA) of telescopes, New Mexico, USA.
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Sharmila Goedhart, an astronomer at HartRAO. |
Christina Langa, a MSc student, who is doing her research
at HartRAO.
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They can unravel signals from pulsars, quasars, masers, distant galaxies and other mysterious objects in the universe. They use the information to study the birth and death of stars, the violent lives of galaxies and sometimes even to hunt for extraterrestrial life.
Pulsar - a collapsed star producing beams of
radio waves. |
Quasar - radio-emitting hot gas jetting out from a
supermassive black hole in the centre of a galaxy. |
Masers from
hydroxyl molecules in the gas ejected from a dying star. |
Distant galaxies
An image of how a radio telescope array sees a distant galaxy
in which there is a black hole producing jets. Credit: NRAO.
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Radio waves are the same sort of waves as light. The difference is the
length of the waves is much longer than it is for light. For example, the
radio waves your FM radio receives have a wavelength of 3 metres, and your
microwave oven produces radio waves with a wavelength of about 10
centimetres.
Radio emission along the plane of the Milky Way. |
A radio telescope is a very sensitive receiver of radio waves. It has two basic components to help us to decipher the meaning of the radio waves that it detects:
- A dish-shaped antenna is pointed to the sky to collect the radio waves. Because the strength of the radio waves that reaches the earth is very weak - they have come from a long way away! - the collecting area should be large. The curved surface of the antenna then reflects the radiation to the focus point of the dish, where it is received by a metal horn and fed to a sensitive radio receiver.
- The receiver then amplifies the radio signal and digitises it - turns it into numbers - so that it can be stored in a computer.
Radio telescope dish. |
Microwave feed horns (on the right) collect the radio waves arriving at
the focus and feed them into pipes (waveguides) that carry them to the
amplifiers.
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This information is then processed with the help of computers. To help make sense of the strings of numbers, astronomers turn the numbers into pictures. Each of these numbers represents information from a specific point in space. Astronomers often assign specific colours to these numbers according to the amount of information they represent. They then combine the colours to make a picture so that they information can then be "seen". These pictures tell us about many characteristics of the objects in the universe.
The sky seen at optical wavelengths is dominated by stars and the Milky Way - itself
composed of billions of stars. Source: Lund Observatory |
The sky seen at radio wavelengths is dominated by radio emissions from clouds of hot
gas in the Milky Way and from distant galaxies containing supermassive black holes spitting out jets of hot gas.
Courtesy Justin Jonas, Rhodes University / SA SKA
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Radio telescopes usually study what is invisible to optical telescopes,
and optical telescopes usually study what is invisible to radio telescopes.
There are many exciting things you can do if you are interested to work with radio astronomers, or perhaps be involved in designing one of the telescopes of the future.
- Astronomers and astrophysicists study physics for several years and then go on to advanced training in astrophysics. They are the people who decipher the meaning of the signals. It's a bit like rocket science, but just think of having the universe as the lab where you work! They write the computer programs to run the telescopes and to get information from the data coming from the telescopes.
- Engineers help to design and build components for existing and new telescopes. They also develop the sophisticated software and computer systems needed to operate the telescope.
- Technicians are important members of a telescope team. They help to make new components and make sure everything on the telescope is working well.
People cause a lot of radio wave interference with their cell phones, radio and television broadcasts, air traffic, and many other radio devices. Therefore, radio telescopes must be built as far away as possible from big cities.
South Africa has a 26-m diameter radio telescope (that's a huge dish!) at the Hartebeesthoek Radio Astronomy Observatory in a valley west of Krugersdorp. Hills around this site help to shield the radio telescope from radio signals from Tshwane and Johannesburg, for example from microwave ovens and cellphones.
The surface of the 26-m radio telescope with onlookers seen from above. |
The 26-m radio telescope at the Hartebeesthoek Radio Astronomy Observatory.
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Over the next three years the country is also building an exciting new radio telescope, called the Karoo Array Telescope, near Carnavon in the Northern Cape. This new telescope will have 20 dishes, each of them 19 m high and 15 m in diameter.
Artists impression of the Karoo Array Telescope. |
But, most exciting of all, we are in the race to host the world's largest ever radio telescope, the Square Kilometre Array, or SKA. This mega telescope will have thousands of dishes, spread over thousands of kilometres. South Africa is competing against Australia in this project. If we win the SKA bid, it will be like winning the SCIENCE WORLD CUP!
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| An artist's impressions of part of the core of the SKA. Tile-shaped antennas making up the central focal plane array is surrounded by dish-shaped antennas. The SKA will consist of thousands of antennas, spread over 3 000 kilometres. About half of the antennas will be in a central region about 5 kilometres across. Photographs: Xilostudios |
You can't do it without mathematics and physical sciences! With a matric exemption in both of these subjects at higher grade, you'll be off to a good start. Computer science will also help! At university you will study astronomy and physics, before going on to more specialised postgraduate studies.
Sources
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