Radio Telescope | Universe Today

Written by Tammy Plotner

Do you think a radio telescope is used for getting closer look at your favorite rock and roll station? If you're curious about what a real radio telescope does, what type of signals it picks up, what it's used for and more, then you've come to the right place! Follow along as we take a brief look at the history of the radio telescope and all its different types…

The First Radio Telescope

The first radio telescope was accidentally built by Karl Jansky while working at Bell Telephone Laboratories. His job was to try and identify different types of static which might be interfering with radio telephone service. Jansky first antenna pointed in all different directions and after months of study he categorized the strange static into three sources: near electrical storms, far electrical storms and a steady, predictable hiss he couldn't quite identify that repeated every 23 hours and 56 minutes. By comparing his notes to astronomical maps, Jansky soon learned he was receiving radio "noise" from the Milky Way!

Types of Radio Telescopes

Because the range of radio frequencies in the electromagnetic spectrum is very broad, the size and types of radio telescopes varies greatly. Most radio telescopes are directional – pointing the receiving end or focal point towards the signal source. If the radio telescope is meant to receive a long wavelength, the material can be very coarse – such as wide wire mesh or even an arrangement of wires. Shorter wavelengths need more collection surface, such as a solid "dish". Like an optical telescope, the larger the dish is, the more resolution of signal is received. Resolution – or a clearer, better signal – is the reason that ever larger dish arrays are built, such as the radio telescope at Green Bank or Aricebo.

Another type of radio telescope is called an interferometer. Instead of a single, large dish, an array – or alignment – of many parabolic radio telescopes are joined together. Not only does this increase the amount of signal that is collected, but the technique works by superposing (interfering) the signal waves from the different telescopes on the principle that waves that coincide with the same phase will add to each other while two waves that have opposite phases will cancel each other out.

What Does A Radio Telescope Listen To?

Almost all astronomical objects that can be seen visible light also emit radiation at radio wavelengths and many objects that can't be seen can visibly be seen in radio. Radio telescopes not only listen to objects such as pulsars and quasars but they are able to "image" galaxies and nebulae. Even planets have radio emissions!

Radio telescopes pick up synchrotron emission from galaxies and are able to paint portraits in false color light of these energetic cosmological wonders. Quasars are some of the most distant things in our Universe while pulsars give off such perfect sets of radio signals that they can even be used for time keeping! Scientist use the information they gather with radio telescopes to discover more about how our Universe formed, how it is expanding and what else might be out there.

Planets give off radio signals, too! A favorite radio telescope of many amateurs is called the Radio JOVE project. It is a simple dipole antenna and a receiver that also picks up radio signals from the Milky Way and from our Sun as well.

Filed under: Astronomy

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