Radio Telescope: Definition, Parts & Facts

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  • 0:00 What is a Radio Telescope?
  • 1:41 How Does a Radio…
  • 2:51 Interferometry
  • 4:04 Lesson Summary
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Lesson Transcript
Instructor: David Wood

David has taught Honors Physics, AP Physics, IB Physics and general science courses. He has a Masters in Education, and a Bachelors in Physics.

This lesson will explain what a radio telescope is, how radio telescopes work, the parts that make them up, what each of those parts does, and why radio telescopes are important.

What Is a Radio Telescope?

When astronomers first looked at the stars and began to ask questions about what their observations meant, they only really had one tool in their arsenal: the optical telescope. These kinds of telescopes use lenses or mirrors to gather visible light from above and create a magnified image. But the electromagnetic spectrum contains a lot more than visible light.

Once we realized that there was more than our eyes could see, that there were radio waves, microwaves, infrared, ultraviolet, x-rays, and gamma rays, we started to look for ways to view the night sky in these parts of the electromagnetic spectrum. Radio telescopes were one of the first successes in that area.

A radio telescope is similar to the radio in your car, but is much bigger, more sensitive, and able to create a visual picture of the signals it receives. Radio telescopes create a picture of the sky, not in visible light, but in radio waves. This is extremely useful, because there are objects that can't be seen through visible light, objects that we wouldn't even know were there without radio telescopes.

Radio telescopes look very much like gigantic satellite dishes. Because radio waves have such long wavelengths, their surfaces don't even need to be fully solid -- a wire mesh will suffice, because the waves are too big to fit through the gaps. Radio telescopes also have to avoid interference, and so tend to be placed away from cities, hidden away in valleys to block radio signals from Earth.

But how exactly do radio telescopes create a picture from nothing more than radio waves?

How Does a Radio Telescope Work?

A radio telescope has several main parts: a dish and antenna, a receiver, a detector, and an analyzer.

The dish collects the radio signals from space and focuses them on the antenna. A larger dish will collect more radio waves and lead to a stronger signal at the antenna, so radio telescopes can be huge. The largest individual radio telescope dish in the world is the Arecibo radio telescope located in Puerto Rico, which has a diameter of 305 meters!

The receiver takes the radio waves received by the antenna and converts them to electrical signals (voltages). The receiver has to be extremely sensitive, and modern receivers are often kept at below-freezing temperatures, as low as -270 degrees Celsius, to reduce noise from the motion of atoms in the metal.

The detector measures the power density of the electrical signal, which is the necessary to turn the signal into a photo. A higher power density translates into a brighter part of the image.

The analyzer, usually a computer or a device attached to a computer, takes the data and creates an image from it.

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