The Lake County Astronomical Society

Astronomy Bio...Anthony Hewish

Jay Bitterman

Anthony Hewish was born on May 11, 1924, in Fowey, Cornwall. He first attended King's College, Taunton and in 1948 he graduated from Gonville and Caius College at Cambridge

Prior to 1950, Hewish's experimental work was directed particularly to the study of the solar atmosphere using radio telescopes. He examined the Sun's outer corona using simple corner reflectors to discover the electron n density of its atmosphere, and to analyze the irregular hot gaseous clouds of plasma surrounding it.

While working at the Telecommunications Research Establishment in Malvern, he met Martin Ryle, who was later to become Astronomer Royal. They became members of a research team that was involved with a series of intensive solar and interstellar surveys, by radio, at the Cavendish Laboratory in Cambridge. The surveys were published as the First, Second, Third, and Fourth Cambridge Catalogues.

Through the efforts of Ryle, new instruments became available and radio observations were extended to sources other than the Sun. In particular, Hewish examined the fluctuation in such sources of the intensity of the radiation (the scintillation) resulting from disturbances in ionized gas in the Earth's atmosphere, within the solar system, and in interstellar space.

In the 1960s, Hewish instituted research into radio scintillation at the Mullard Observatory and discovered the first pulsar. In 1972 he became Professor of radio astronomy at Cambridge University.

While occupied in this research at Mullard Observatory, one day in 1967 Hewish's attention was drawn by a research student, Jocelyn Bell, to some curiously fluctuating signals being received at regular intervals during the sidereal day. On November 28, 1967, he installed more sensitive high-speed recording equipment that revealed the first indication of a pulsed emission whose fixed celestial direction ruled out the possibility of an artificial source. In early December he confirmed the November data and verified that he and Bell had discovered pulsating radio stars, or pulsars.

In February 1968 Hewish published a more detailed account of the results, by which time he identified three additional pulsars. His investigation revealed that pulsars are sources of radio emission in our galaxy, which emit radiation in brief pulses. Although a pulsar will emit radiation with nearly constant pulsation periods, the rate of emission differs between pulsars, as does the "shape" of the pulse. Pulses could be single, double, and even triple peaked. Shapes can differ within each pulsar, but the mean pulse shape generally changes only very slightly to decrease the interval over many months.

Comparative studies of successive shapes have shown that each pulse itself is made up of two pulsatory constituents: a regular one (class 1), and another (class 2) pulsating at irregular frequency within the first one.

It is now generally accepted as originally proposed by Thomas Gold and others that pulsars are rotating neutron stars (stars that are nearing the end of their stellar life, having practically exhausted their nuclear energy). It remains less clear how rotational energy is converted to emission of such shapes and such intensity as have been discovered, although many hypotheses have been put forward.

Hewish's initial discovery of four pulsars began a period of intensive research, in which more than 170 pulsars have been found since 1967. In the meanwhile, Hewish has patented a system of space navigation using three pulsars as reference points that would provide "fixes" in outer space accurate up to a few hundred kilometers. He continues to work in radio astronomy.

In 1947 Hewish and Martin Ryle were jointly awarded the Nobel Prize in Physics for their research into the radio scintillation that resulted in the discovery of pulsars.