What is radio astronomy?

radio astronomy
noun
  1. the branch of astronomy concerned with radio emissions from celestial objects.

I have joined the radio astronomy branch of Mansfield and Sutton Astronomical Society.  24 hours ago I had never even heard of radio astronomy. My first task is to learn what it is and what it involves.

A little history

In August 1931 American physicist Karl Jansky detected radio waves from space, and so began the age of radio astronomy. A wide range of sources emit radio waves from our nearest star the sun, to radio sources billions of light years away. In fact the sun is a powerful radio source due to its close proximity to earth. It was radio astronomy that lead to the discovery of pulsars in 1967 by Cambridge University student Dame Jocelyn Bell Burnell.

How do radio telescopes work?

Light is a relatively short wavelength where as radio is a much longer wavelength. This means that radio dishes do not have to be constructed to such high production specifications, they do however have to be bigger than light detecting scopes. The largest radio telescope in the world is the Arecibo telescope in Puerto Rico.

In terms of the actual function of a radio telescope, the Australia Telescope National Facility gives this explanation;

A radio telescope is simply a telescope that is designed to receive radio waves from space. In its simplest form it has three components:

  1. One or more antennas to collect the incoming radio waves. Most antennas are parabolic dishes that reflect the radio waves to a receiver, in the same way as a curved mirror can focus visible light to a point.
  2. A receiver and amplifier to boost the very weak radio signal to a measurable level. These days the amplifiers are extremely sensitive and are normally cooled to very low temperatures to minimise interference due to the noise generated by the movement of the atoms in the metal (called thermal noise).
  3. A recorder to keep a record of the signal. Most radio telescopes nowadays record directly to some form of computer memory disk as astronomers use sophisticated software to process and analyse the data.

Advantages of radio over optical telescopes

Radio astronomy can measure signals in bad weather or when the sky is cloudy, a major benefit in cloudy England. They can also measure signals from objects obscured by space dust, and detect clouds of invisible gas. In terms of setting up a home system they are one of the most affordable ways in to astronomy with home made antennas starting at about £30, though you will need a computer to process the signals received.

What can a radio telescope discover?

Radio telescope output that has been translated to an audio signal sounds just like the static you hear when your television is tuned to a channel where no station is present. It is this broad noise signal that is of interest to radio astronomers who measure it in many ways, but only listen in perhaps to hear what kind of man-made interference is messing up their measurements.

Some things that are detected are

 

  • Study Jupiter’s noise storms.
  • Record flares and predict geomagnetic activity.
  • Detect a pulsar using DSP (digital signal processing).
  • Detect stronger radio sources.
  • Look for HEPs (high energy pulses} from the galactic center.
  • Search for radio correlations to gamma ray bursts.
  • Study ionospheric scintillation and refraction.
  • Detect meteors invisible to the eye.
  • Develop a long base line interferometer

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