Biggest Star

The sun, 864,000 miles in diameter, could contain a million bodies the size of the earth. Yet the sun, though of higher than average luminosity, is rather on the small side as stars go, being officially classed as a "yellow dwarf." For a really big star astronomers look to Antares, a red supergiant 400,000,000 miles in diameter. All stars are globes of hot gas. Antares is relatively cool, its gaseous density very low. Thirty-seven thousand cubic feet of its star-stuff, if concentrated and brought to earth, would weigh only one pound. Yet up to last week it held rank as the largest star known to astronomy.

Last week Antares dropped to second place as news came out of University of Chicago's Yerkes Observatory at Williams Bay, Wis. of a stellar monster four billion miles through the middle. If its centre were placed at the hub of the solar system it would engulf all the planets up to the last and most remote pair, Neptune and Pluto.

Discovered by Dr. Otto Struve, Rus-sian-born director of Yerkes, and two associates, the big star is an obscure companion of Epsilon Aurigae, a well-known star not far from Capella. Even more diffuse than Antares, it is believed to have a temperature of only 1,000DEG C., lowest of any star known. Around the main body of the star is a shell of gas electrified by light from Epsilon Aurigae, in the same way that the electrified shell or "radio mirror" around earth is maintained by radiation from the sun. This phenomenon has never before been observed in a stellar atmosphere. Actually, Epsilon Aurigae's monstrous, almost transparent companion has not yet been seen or photographed. It was deduced from spectrographic observations made on Epsilon Aurigae. Its size, constitution and temperature were determined after it passed in front of Epsilon Aurigae in 1929-30, like a cloud in front of the moon. It took nine years for the Yerkes people to evolve a conclusion about this unique star which would fit the observed facts.

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