From the archive, 24 May 1955: Discovery of a new supernova

There are so many stars in the sky that the discovery of yet another may not seem of very great importance. Yet the one whose discovery Professor Hans Haffner, of Hamburg University, announced yesterday is no ordinary star. In our own galaxy only three stars of this kind have been seen in the last thousand years. The star is a supernova. Observationally a supernova is the sudden appearance of a brilliant star-like object in a part of the sky where no star was previously visible. The new star increases rapidly in brightness for a period of weeks or months, and then starts to lose its brightness until it becomes invisible to the naked eye or in the less powerful optical instruments.

Yet appearances are misleading. For the supernova is nothing other than the explosion of a whole star of about the same size as our sun.

The new supernova is said to lie in the constellation of the Serpent, and to be at such a distance that it has taken the light from the explosion three million years to reach us. Nevertheless this distance is not great in comparison with other astronomical distances, and it seems probable that the new supernova must lie in one of the galaxies that are close neighbours of our own. So far the star is invisible to the naked eye and will probably remain so even when it has attained its maximum brightness. But it will undoubtedly present astronomers with a valuable opportunity of studying a very rare phenomenon. These events are so rare that it has not yet been possible for astronomers to study one at what might be called close hand. The first recorded observation of a supernova was made by the Chinese astronomers in 1054. They observed the sudden appearance of a bright star in the sky. For more than a year it increased in brightness and all sorts of astrological interpretations were made. But after two years could no longer be seen and the Chinese reasonably concluded that it had ceased to exist.

Fortunately they had kept good records of their observations and these proved of great value when it was discovered in the last century that that particular part of the sky was occupied by a strange nebula, a glowing mass of what appeared to be gas. This nebula, called the Crab Nebula, was so different from other astronomical objects that it could not be fitted into the accepted system of astronomy. But as observation continued it was realised that the gas was expanding at a very great speed – more than a thousand kilometres a second.

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