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Introduction to radio astronomy
Introduction to radio astronomy
Radio astronomy is the study of celestial objects at radio frequencies. The first radio waves from astronomical objects were detected by Karl Jansky in 1933. He was assigned a project for Bell Telephone Laboratories to study the effects of static (noise) with radio voice transmission.
Using the rotating directional antenna seen in the image, he studied signals from different directions for several months. The static signals he detected were characterised into three different types of static: nearby thunderstorms, distant thunderstorms, and a faint static hiss of unknown origin. After more than a year of trying to figure out where the static hiss was coming from, he pinpointed it as being the centre of our galaxy in the direction of the constellation Sagittarius. Sparking the beginning of radio astronomy as we know it.
Karl Jansky and his rotating directional antenna used to detect radio emissions from the Milky Way (early 1930s). Image courtesy of NRAO/AUI
Karoo Array Telescop-7 (KAT-7)
What are Radio Telescopes?
Radio Telescopes are very sensitive wideband radio frequency (RF) receivers
They are used to detect and image faint signals from galactic sources such as galaxies, gas, pulsars, stars, etc
Radio Telescopes detect very small signals, measured in Jansky (Jy = 10−26 W⋅m−2⋅Hz−1 )
Basic operation of a radio telescope
How does it work?
Radio Telescope use a large DISH to receive radio signals from distant celestial radio sources
These very small signals are then converted to electronic (digital) signals and sent to the electronic systems where it is eventually displayed and stored
Scientists use the stored data to do investigations into various cosmic structures and events.
Radio telescopes are used because they can detect invisible gas, and can reveal areas of space that may be obscured with cosmic dust.
Being able to see more than just the visible spectrum allows for a wider range of possibilities, as depicted in the image below.
MPI Dish
Atmospheric opacity as a function of wavelength- It can be seen that between approximately 5 cm (6 GHz) and 10 m (30 MHz), the atmospheric opacity is the least. Image by NASA.
SKA-Mid locations:
SKA-Mid locations:
The current 64 SKA-mid telescopes are situated near the town of Carnarvon in the Karoo.
The site is not open to the public, however, using Google Maps, much of the region can be explored.
This area was selected due to the low level of man made radio frequency interference (RFI).
SARAO Website (www.sarao.ac.za) showing the extent of activities related to Radio Telescopes in the Karoo including:
Science discoveries
International co-operation
Academic opportunities
Detrimental Effects of Rfi
Detrimental Effects of Rfi
Radio frequency interference is a one of radio telescope's biggest enemies. To learn more about this, click the button below!
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