History
Karl Jansky first discovered radio waves in 1931. In the late 1930’s an
American engineer named Grote Reber built the first-bowl shaped radio telescope
and operated it in his backyard. His radio telescope collected and measured
radio waves given off by objects in space.
Discoveries
Scientists discovered that the Sun and the center of the Milky Way galaxy
were strong sources of radio waves. Radio Telescopes also detected strong radio
waves coming from black or dark places in space. These were discovered to be
exploded stars and a rare type of distant galaxy.
How Radio Telescopes Work
Radio telescopes can produce images of objects in space that would have been
missed by an optical telescope. Optical telescopes need to have some kind of
light to see an object, but radio telescopes don’t need light to
"see." Radio telescopes helped discover pulsars (collapsed stars that
send out regular pulses of radio waves) and quasars (extremely distant star-like
objects that produce an enormous amount of radiation).
Many radio telescopes use a bowl-shaped reflector called a dish to collect
radio waves from space. The reflector focuses the waves onto an antenna that
changes them into electric signals. A radio receiver amplifies these signals and
records their strength at different frequencies and from different directions.
The information is analyzed by a computer to draw a picture of the source of the
radio waves or to analyze the chemicals found in the source.
Large radio telescopes are also used as giant radar systems to map the
surfaces of the Moon and planets. Scientists send radio waves into space to
bounce them off of moons, planets, or other objects. Receivers record the radio
echoes that bounce back to Earth. Astronomers call this technique "radar
mapping."
Radar mapping works the same way as an ultrasound with a baby. The machine
will bounce sound waves off the baby inside the mother, and when it bounces
back, it will form a picture. The sound is a vibration and when the machine
picks up the vibration bouncing back, it is catching the echo. It is also like a
fish detector. The fish detector sends out a sound wave. The fish detector
collects the sound wave when it comes back. The computer in the fish detector
can tell you how far the fish are, depending on how long it took the sound wave
to travel back to the boat.
