Monday, Mar. 30, 1936

Super-Nova

If a giant star, sailing through the sea of space, were a battleship a million miles from stem to stern, and some spark set off its powder magazine, the result would be something like what happens when a star explodes as a supernova. Supernovae are the mightiest celestial cataclysms known to man. Last week astronomers at Mt. Wilson Observatory in California reported discovery and observation of a super-nova in the distant island universe NGC 4273. Although about a dozen supernovae have been found by chance on photographic plates, the one announced last week was the first since 1901 to be watched during its performance and the second since the invention of the telescope.

The lesser star explosions called novae are fairly common. About 40 have been detected since 1900. Nova Herculis, which blazed up in 1934, attracted much attention because it was only about 1,500 light-years from Earth (TIME, Dec. 31, 1934). At its peak one of the twelve brightest stars in the sky, it offered superb opportunities for spectroscopic examination. Such novae throw off tremendously hot shells of gas, then subside irregularly and gradually to something like their former faintness. On the other hand some astronomers believe that supernovae, which fade rapidly, become "neutron stars"--small, dead, dense lumps of matter, forlorn wraiths of the cosmos.

Astronomers do not know why stars blow up. For some reason the interior seems to start releasing energy faster than the surface can radiate it. Something of the sort happened to a star in NGC 4273 long before the first men appeared on Earth. Light from the blow-up started toward Earth at 186,000 miles per second, sped on for 7,000,000 years. Thirty thousand years ago it reached the fringe of the Milky Way. Four years ago it was inside Proxima Centauri, Earth's nearest star. Going fast enough to circle Earth seven times in a second, the light took only 5 hr. 30 min. to cross the outer solar system.

Last January it struck a photographic plate under Mt. Wilson's 100-inch telescope, where its record was observed by famed Edwin Powell Hubble. Because of its great distance the star never approached naked-eye visibility, faded rapidly in late February. But Dr. Hubble's coworker, Dr. Milton LaSalle Humason, took spectroscopic and photometric observations which indicated that at the peak of its long-ago death agony the super-nova was 50 times as hot and 10,000,000 times as bright as the sun.

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