Radio Astronomy
Scientists Use Radio Wavelengths to Study Celestial Phenomena
Instead of optical telescopes, astronomers use antennas and computers to study the Universe at wavelengths invisible to the human eye. So, how does that work?
When astronomers use optical telescopes to look at objects in the sky, they see the visible light those objects are emitting, (or reflecting, as in the case of the moon or terrestrial planets). When astronomers use radio telescopes to look at those objects, they see the radio waves those sources emit, and the objects take on a different look.
Visible light and radio waves are both examples of electromagnetic radiation: energy that travels and spreads out as it goes.
Electromagnetic Spectrum
Scientists have assigned names to various wavelengths of this radiation and put them on a continuum, much like a number line, to make them easier to talk about. This continuum is called the Electromagnetic Spectrum. Radio wavelengths are at the long end of the Spectrum. As wavelengths shorten, the energy increases, through infrared, optical (also called visible), ultra-violet, x-rays, with gamma rays being the most energetic of all.
The only portion of the Electromagnetic Spectrum we can see with our eyes is that part comprised of the visible light wavelengths. We see each wavelength as a different color. The longest wavelengths we can see are red, about 700 nanometers (billionths of a meter) in length. It would take about 33,000 of them to cover an inch of space. At the other end of the visible spectrum is violet: 400 nm long. 66,000 of them would cover an inch of space.
Radio Waves are not Sound Waves
Radio waves are much longer, but they are still a form of energy that we “look” at through a conversion by computers or other instruments. It is easy to confuse radio waves with sound because when you turn on a radio, you hear sound! But if you stand outside a radio broadcasting station, next to the transmitter, you do not hear the DJ’s voice being transmitted. Instead, the transmitter is generating radio waves at a frequency specific to that radio station (such as 99.5 FM). The sound waves of the DJ’s voice are encoded on those electromagnetic waves, to be stripped off and decoded by the electronics in your radio.
Radio Astronomy Requires Specialized Equipment
Astronomers use equipment to measure the strength of radio waves at specific frequencies that are emitted by celestial objects. The waves are collected by antennas which vary from simple wires to complicated dishes and receivers. To gain a clear understanding of objects in space, scientists need to “see” those objects at as many wavelengths as possible. These instruments enable astronomers to “see the invisible,” to study celestial objects at radio wavelengths: to “do” radio astronomy.
To learn more about radio astronomy, check out the information on the website for the National Radio Astronomy Observatory.
