Born in Cornwall, Hewish attended King's College, Taunton, and Cambridge University. Upon graduating in 1948, he went to work for the Telecommunications Research Establishment before returning to Cambridge to become part of a team undertaking solar and interstellar research by radio. At first, Hewish used radio telescopes to study the atmosphere of the Sun. He determined the electron density of the Sun's corona and studied the hot plasma that comprises this part of the Sun's atmopsheres.
After 1950, new instruments became available that allowed for studies beyond the Sun. Hewish examined how radio sources were received on the Earth; often these sources were disturbed by ionized gas in the Earth's atmosphere or by interstellar disturbances. The study of these disturbances led to the discovery of pulsars. In 1965 Hewish designed a new kind of radio telescope to detect quasars and assigned Jocelyn Bell, one of his graduate students, the task of bringing the telescope on line. As her work progressed, Bell began receiving unwanted radio noise that Hewish thought stemmed from local ham operators or other electrical interference. After eliminating that possibility, Hewish tried to locate the signal's position in the sky. He found that the source was located outside the solar system and that the signals arrived at regular intervals of 1.337 seconds. In jest, he and Bell named the source LGM 1 (Little Green Men 1). Bell continued searching the sky and found other independent sources.
Of course, the debate over the origin of these radio signals was immediate when Hewish and Bell announced their discovery in 1968. Hewish thought they might come from white dwarf stars. Later in the year, however, others suggested the signals were due to a rapidly rotating neutron star rather than a pulsating white dwarf. This theory is the one generally accepted today: a large star near the end of its life explodes, leaving a small, extremely dense star behind. This remnant has a strong magnetic field that captures radiation and channels it into space along narrow beams that may sweep past the Earth if the neutron star's axis rotation is inclined at the proper angle with respect to our planet. The beams of radiation are detected as they sweep around, much like the beam of a lighthouse. The pulses correspond to the speed of the star's rotation and can range from 0.033 seconds to 4 seconds.
The discovery of pulsars and neutron stars gives astronomers an opportunity to examine matter under extreme conditions of pressure and temperature. Work on pulsars has led to research on other aspects of stellar evolution: white dwarfs, collapsars, frozen stars, and black holes.
Hewish has patented a system of space navigation as a result of his work on pulsars. He uses three pulsars as a reference point to provide "fixes" in outer space accurate to within a few hundred miles. For his work in the field, Hewish shared with Martin Ryle the 1974 Nobel Prize for Physics.
Hewish has remained active in his field, and in 1998 was elected a fellow of the Institute of Physics. He is currently on emeritus status at the Cavendish Laboratory's Astrophysics Department.
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