Radio Waves

• How Large are Radio Waves? Of all types of light, radio waves have the longest wavelengths. Radio waves are longer than 1 mm and can be very long.
• In fact, the most common radio emission in the galaxy is at 21 cm, (about the length of the average forearm). This radiation is produced by hydrogen atoms.
• Astronomers use the 21 cm radio radiation to probe the gas and dust located between stars.
• Good Sources of Radio Waves: Hydrogen atoms, like we mentioned, are good sources of radio waves. Other sources of radio emission are from stars like our Sun. Distant galaxies or quasars (luminous objects at the center of some galaxies) can also be bright radio sources.
• Radio telescopes have to be large in order to capture these long waves. Scientists and engineers sometimes build several dishes that they hook up together to capture or record radio waves with more detail than single dishes can provide. These are called "arrays."

• The Very Large Array located in Socorro, New Mexico is one of the world's premiere astronomical radio observatories. The VLA consists of 27 antennas arranged in a huge Y pattern up to 36km (22 miles) across -- roughly one and a half times the size of Washington, D.C.