Radio Waves from Space
by SpaceHike.comMore articles in Telescopes
Karl Jansky discovered radio static coming from the Milky Way in 1932, and this was the beginning of radio astronomy. The British scientist, Stanley Hey, heard strong radio outbursts from the Sun in 1942, and in 1949, the first radio sources outside our solar system were detected by radio astronomers in Australia.
With the assistance of radio astronomy, some of the most explosive and energetic objects in the universe have been discovered. This included radiation from the Big Bang, supernovae remains, and super-massive black holes. Radio telescopes have the ability to find molecules in space. These molecules are the raw materials for the beginnings of new life and new planets. Remains of a supernova create radio waves by high speed electrons that become trapped in magnetic fields. This type of radio wave is called synchrotron radiation. It is strongest at the longer wavelengths. It is forbidden for anyone to broadcast on the wavelengths used by scientists to study the universe. Radio telescopes have an enemy with increasing power-radio pollution, which comes from cell phones, to name only one source.
For scientists to study radio waves, the waves need to hit the inside of a large dish, which then reflects and focuses onto an antenna. The antenna will produce electrical signals that are sent out to a computer. The computer will store these signals and then convert the signals into electronic images. There is more to this process than simply listening to radio wave static.
Japan has a dish that is 45 meters in diameter and covers more than ten times the area of a tennis court. It is named Nobeyama Radio Observatory. The telescope has a smooth surface and it has been accurately formed to less than the width of a blade of grass. The precision of the surface allows the dish to focus radiation. It is so precise that it can focus radiation of millimeter wavelengths from gas molecules in space between the stars.
The drawback to radio telescopes is the fuzzy view compared to optical telescopes. This results from radio waves being so much longer than light waves. Scientists compensate for this by synchronizing several small telescopes. The Very Large Array has 27 dishes that can be moved along three railroad tracks. The maximum distance is approximately 36 km apart. The Very Long Baseline Array provides an even sharper image than the Hubble Space Telescope. The VLBA stretches across the United States.
The single line of telescopes will leave gaps that may cause the final radio picture to be distorted. A solution was suggested by Martin Ryle in the 1950s: rather than taking snapshots views that were full of holes, the telescopes would observe the same radio source for twelve hours. When the Earth rotates, each telescope would be carried around the others in a slow half-circle. This provided a synthesizing of the larger telescope parts.
Harvard scientists found a 21 cm signal sent out by hydrogen in the Milky Way in 1951, and the first quasar was discovered in 1963. The first interstellar molecule, hydroxyl, was discovered in 1963 by its radiation wavelength. The first pulsar was found in 1967 by Tony Hewish and Jocelyn Bell Burnell. The Cosmic Background Explorer measured the cosmic background radiation ripples in 1992.
1. Couper, Heather and Nigel Henbest. Space Encyclopedia DK Publishing, Inc.: NY 1999
2. Editors. Secrets of the Universe. International Master Publishing: US. 1999