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Frequently-Asked Questions About Radio Astronomyand NRAO

What is radio astronomy?

You can read this screen because your eyes detect light. Light consists ofelectromagnetic waves. The different colors of light areelectromagnetic waves of different lengths.

Visible light, however, covers only a small part of the range of wavelengths in whichelectromagnetic waves can be produced. Radio waves are electromagnetic waves of muchgreater wavelength than those of light.

For centuries, astronomers learned about the sky by studying the light coming fromastronomical objects, first by simply looking at the objects, and later by makingphotographs. Many astronomical objects emit radio waves, but that fact wasn't discovereduntil 1932. Since then, astronomers have developed sophisticated systems that allow themto make pictures from the radio waves emitted by astronomical objects.

A number of celestial objects emit more strongly at radio wavelengths than at those of light,so radio astronomy has produced many surprises in the last half-century. By studying thesky with both radio and optical telescopes, astronomers can gain much more completeunderstanding of the processes at work in the universe.

What is the National Radio Astronomy Observatory?

The National Radio Astronomy Observatory (NRAO) is a facility of the National Science Foundation, operated byAssociated Universities,Inc., a nonprofit research organization. The NRAO provides state-of-the-art radio telescope facilities for use by the scientific community. Weconceive, design, build, operate and maintain radio telescopes used by scientists from around the world. Scientists use our facilities to studyvirtually all types of astronomical objects known, from planets and comets in our own Solar System to galaxies and quasars at the edge of theobservable universe.

The headquarters of NRAO is in Charlottesville, Virginia, and the Observatory operates major radio telescope facilities in Green Bank, WestVirginia; Socorro, New Mexico; and Tucson, Arizona.

What are you listening to?

Actually, nothing! While everyday experience and Hollywood movies make people think of sounds when they see the words "radio telescope,"radio astronomers do not actually listen to noises.

First, sound and radio waves are different phenomena. Sound consists of pressure variations in matter,such as air or water. Sound will not travel through a vacuum. Radio waves, like visible light, infrared,

ultraviolet, X-rays and gamma rays, are electromagnetic waves that do travel through a vacuum. When youturn on a radio you hear sounds because the transmitter at the radio station has changed thecharacteristics of the radio waves to make them carry information about the sound of voices and music.

Your radio receives the radio waves, decodes this information and changes it back into audible sounds.

The VLA and the VLBA are designed to produce images of celestial bodies. Just as photographic filmrecords the different amount of light coming from different parts of the scene viewed by a camera's lens,our radio telescope systems record the different amounts of radio emission coming from the area of thesky we observe. After computer processing of this information, astronomers can make a picture.

No scientific knowledge would be gained by converting the radio waves received by our radio telescopesinto audible sound. If one were to do this, the sound would be "white noise," random hiss such as that you hear when you tune your FM radiobetween stations.

What have you discovered lately?

A lot! For some of the highlights, look at NRAO's press releases about recent research results. Every year, hundreds of scientists useNRAO's radio telescopes, and they report their results in numerous papers in scientific journals. Almost any introductory astronomy textbookwill contain images and tell of research results from NRAO's various radio telescopes.

VLA? VLBA? How did you come up with these names?

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The VLA got its name because it is an array of radio telescopes and it is very large. In its very early conceptual and planning stages, "VeryLarge Array" was a working title, probably not intended to be the final name for the facility. However, after a few years, the name stuck.

At the VLA, all of its 27 dish antennas work together as a single instrument. The signals from all antennas are brought together in real timethrough a microwave communication system that uses buried waveguide. As radio astronomers sought to increase their resolving power, orability to see fine detail, by separating their antennas by even greater distances, it became impractical to bring the signals together in realtime. Instead, tape recorders and precise atomic clocks were installed at each antenna, and the signals are combined after the observation

is completed. This technique is called Very Long Baseline Interferometry(VLBI). When astronomers wanted to build a continent-wide radiotelescope system to implement this technique, the name Very Long Baseline Array (VLBA) was the natural working title. Again, it stuck.

Is NRAO doing SETI work?Radio observations as part of a Search for Extraterrestrial Intelligence (SETI) have been done by different groups of researchers for anumber of years, but this type of work is not a part of NRAO observational programs. For the most part, our radio telescopes have beendesigned and built for other astronomical purposes. For example, the VLA and the VLBA are specifically designed for high-resolutionimaging. At the moment, the SETI Institute, a privately-funded organization, is purchasing observing time on the 140-foot radio telescope inGreen Bank, which NRAO is retiring from other research in anticipation of the new Green Bank Telescope coming on-line.

Can I build a radio telescope at home?

Many electronic experimenters have built their own radio telescopes. In fact, the world's second radio telescope was built by an amateur radiooperator, Grote Reber, in 1937. Amateurs use a variety of equipment, sometimes modified satellite receivers and dishes, to build their radiotelescopes. For more detailed information about amateur radio telescopes, contact the Society of Amateur Radio Astronomers.

Amateur radio operators pursue a number of activities that are somewhat related to radio astronomy, including communicating by bouncingradio signals off the Moon and the ionized trails of meteors in the Earth's atmosphere. There also are a number ofamateur radio satellites inorbit. Both the Space Shuttle and the Mir space station carry amateur radio equipment that frequently is used by the astronauts tocommunicate to "ham" operators and classrooms around the world. For general information about amateur radio, including how to obtainyour own license, contact theAmerican Radio Relay League.

I think I'd like to become an astronomer. What training do I need?

The typical training for a research astronomer includes earning a Bachelor's degree in Physics, Astronomy or Mathematics, followed bygraduate school and a Ph.D. in Astronomy or Astrophysics. TheAmerican Astronomical Society, the professional association forastronomers in North America, offers a free brochure on careers in astronomy. High school students interested in astronomy should take asmany courses in science and mathematics as possible in preparation for college.

Can I visit NRAO's Observatory Sites?

Yes. At Green Bank, West Virginia, and at the VLA, near Socorro, New Mexico, we have Visitor Centers open to the public.

Can I get images or data from NRAO's radio telescopes?

Yes, there are some images on the NRAO Web site that you can browse. In addition, images and data from two surveys of the sky made bythe VLA are available on the Internet. You also may download software for viewing these image files. Check out the NRAO VLA Sky Surveyand the FIRST Survey Web pages.

I saw Contact. Was it filmed at the VLA? Where is the canyon I saw in that movie?

Many scenes in Contactwere filmed at the VLA in September of 1996. About 200 filmmakers, including stars Jodie Foster, Tom Skerritt andJames Woods, came to the VLA for the filming. The beautiful canyon seen near the VLA in the movie, however, actually is Canyon de Chellyin Arizona, "moved" to New Mexico by the magic of Hollywood special effects!

Where can I find more information about astronomy?

The World Wide Web is a gold mine of information on astronomy and space science. This includes everything from on-line astronomycourses to archives of thousands of astronomical images. An excellent starting point is theAstroWeb site.

Other sources of astronomical information include your public or school library and monthly magazines such as Sky & Telescope andAstronomy. There may be an amateur astronomy club in your community, and if there is, it is a good place to meet others who are interestedin astronomy and to join activities such as observing with telescopes and hearing lectures on astronomical topics. Your community also may

have a planetarium, public observatory or science museum that can provide information. The Web sites of the two magazines listed abovehave listings of clubs, observatories, planetaria and astronomical events for communities throughout the United States.

Back to the NRAO Home Page

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