Lesson Two : Interferometry
Radio astronomers use interferometry to get resolving power comparable to optical instruments without constructing radio telescopes the size of Africa. Interferometry is the technique of using combined signals from several radio telescopes acting as a single large telescope in order to attain high-resolution images.The Very Large Array (VLA) in New Mexico consists of 27 radio dishes that can be moved on tracks to form an interferometer that is 36 kilometers (22 miles) in diameter.
Very Large Array (VLA)
Courtesy of National Radio Astronomy Observatory / Associated Universities, Inc. / National Science Foundation
Courtesy of National Radio Astronomy Observatory / Associated Universities, Inc. / National Science Foundation
Very Long Baseline Array (VLBA)
Courtesy of National Radio Astronomy Observatory / Associated Universities, Inc. / National Science Foundation
Courtesy of National Radio Astronomy Observatory / Associated Universities, Inc. / National Science Foundation
The Very Long Baseline Array (VLBA) consists of ten large radio dishes in locations across the United States, from Hawaii to the Virgin Islands, forming the equivalent of a radio dish over 8000 kilometers in diameter. That’s about two-thirds the diameter of the Earth! The arrangement of the telescopes that make up the VLBA allows astronomers to achieve extremely high resolving power. From New York, you could read a newspaper in Los Angeles using this telescope (as long as the newspaper was emitting radio waves).