SCENES FROM SCIENCE
Anyone can be wrong
A SUPERNOVA is a star that tempor- arily brightens exceedingly — on occa- sion as a preliminary to exploding. The region at its centre is characterised by very high forces of gravity, under whose influence the debris of the core may collapse into a compact stellar object a 'neutron star' or a 'black hole'.
A neutron star is a star which has undergone gravitational collapse to the extent of being compressed into neut- rons. In their early existence neutron stars, collapsed very small and having intense magnetic fields as well as in- tense gravity, spin. They spin very rapidly, and when doing so emit regular pulses of energy; such stars are known as pulsars. It is to be expected that the pulses of energy would be in the form of electromagnetic waves, radio waves being the obvious form.
However it was thought possible that the regular pulses of energy might take the form of bursts of light waves, Correct: but so far only two faint pulsars have been detected thus. Great excitement, then, in astronomical cir- cles, when Californian astronomers re- ported regular bursts of light from an amazing pulsar at the core of supernova 1987A. Excitement and puzzlement. To emit regular bursts of light with the observed frequency of 1,968 pulses per second, the pulsar had to be spinning at nearly 2,000 revs per second — too fast for the continued existence of a pulsar. Spinning at that speed, according to the astrophysicists, a pulsar would fly to pieces. If it didn't, there was something seriously wrong with theory.
First charge on the experimentalists: check that the observation was accu- rate and repeatable. Unfortunately the signal had been observed in the first instance for only seven hours; and then lost. It was more than a year before it was picked up again, by Californian astronomers in Chile. Now it was rep- eated — repeated when the astronom- ers detected it while aiming their tele- scopes at a different part of the sky! Consternation. It seems the likeliest explanation is that the signal was gener- ated electronically inside the astronom- ers' own television camera, not in space at all. Theory was saved — not so the faces of the astronomers. Any of us can be wrong, and that includes scientists. This incident, though, illustrates how in science, constant scrutiny, constant test- ing by experiment, brings error sooner or later to light. So much the better for science!
William Cooper
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