Learn about the different types of telescopes that astronomers use: X-ray, radio, gamma ray, reflecting and refracting. Learn what the differences are between them and what different things they show us about the universe.

Why Are There Different Types of Telescopes?

Our solar system is an exciting and vibrant space filled with planets, asteroids, comets, black holes, quasars and other wonderful things. Scientists have studied the stars for centuries, discovering new objects and refining their thinking about old ones.

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Astronomers use a variety of telescopes to look at the universe. They need many different types of telescopes to look at space because each telescope shows them different things.

Light comes in wavelengths from short to long. Visible light, the light humans see, is in the middle of the range. Short wavelengths include gamma rays and X-rays. Longer wavelengths include microwaves and radio waves. Most amateur astronomers use optical telescopes, either reflectors or refractors that use light in the visible wave range to show objects.

However, most astronomical research is done on telescopes that look at other wavelengths of light because each wavelength shows something different about the universe.

Radio

It is a bit surprising, but it turns out that objects in space give off radio noise, which just means they emit waves in the radio range of the light spectrum. Radio telescopes look at very long wavelengths of light and convert these waves into pictures.

Radio telescopes collect long-wavelength light to investigate diverse things. Radio telescopes are usually large, dish-type antennas. Scientists build them far away from populous areas to avoid interference from radio and TV. Radio telescopes look at very long wavelength light. You can see many diverse things with radio telescopes. For example, you can investigate how hydrogen gas is distributed in our galaxy and other galaxies, and you can time the rotation period of pulsars.

Radio telescopes convert long wavelengths into pictures.
Radio Telescope Picture

X-Ray and Gamma Ray

X-Ray and gamma ray telescopes collect light in the shorter wavelengths. X-ray telescopes help astronomers study the sun, supernova and other stars, while the gamma ray telescopes study supernovas, pulsars and black holes.

X-ray and gamma ray telescopes don’t work well on Earth’s surface because the short wavelengths get disrupted and weaken in the atmosphere, so scientists like to put these types of telescopes in space where atmosphere is not a problem. X-ray and gamma ray telescopes collect very short wavelength light to see the sun, stars and supernovas.

Reflector

A type of telescope used in most astronomy research is a reflecting telescope. Reflector telescopes use one mirror, or a combination of mirrors, to reflect light and form an image to the viewer. The design of this telescope allows astronomers to see things way out in space that don’t emit much light. Almost all of the major telescopes used in astronomy research are reflectors.

The Hubble Space Telescope (HST) is a reflecting telescope and is currently the largest space telescope there is. It is 43.5 feet long (13.2 meters) and weighs 24,500 pounds (11,110 kg). It was launched into space by the space shuttle in 1990. A few weeks later it became a public relations disaster for NASA when it was discovered that due to an error in manufacturing, the mirror the telescope used had a rather large flaw in it. Eventually the error was fixed when the telescope was serviced in space and given what amounted to a pair of glasses, or contacts, that corrected the problem in 1993.

Reflector telescopes use mirrors to reflect light into images.
Reflector Telescope Design

Refractor

Another type of telescope is the refractor. The refracting telescope uses concave lenses to refract light and make objects appear big and bright. This helps astronomers see the stars, planets and moons. The problem with this type of telescope is that it needs a lot of light to detect objects. In order to collect a lot of light, the lens of the telescope would have to be very large, which would make it very heavy. The lens can only be supported around its edge, and gravity would force the lens to distort under its own weight as it was moved to look at different things in the sky. Refracting telescopes collect visible light to see things out in space, but not as far as reflecting telescopes.

Lesson Summary

Astronomers use many telescopes to see different things in the universe.

Radio telescopes detect long wavelength light and investigate diverse things.

X-ray and gamma ray telescopes detect very short wavelength of light and look at the sun, stars and supernovas.

Reflecting telescopes see visible light and they see things way out in space.

Refracting telescopes detect visible light; they see things out in space but not as far as reflecting telescopes.

Learning Outcome

Once you have finished this lesson, you should be able to describe radio, X-ray, gamma ray, reflecting and refracting telescopes and explain what astronomers use them for.