Astronomy: The Twinkle Belt

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No phenomenon of nature is too small to escape the curiosity of modern science, not even the twinkle of distant little stars. Astronomers call it scintillation. But putting a name to the faint flicker has hardly served to explain it.

For many years astronomers assumed that scintillation was due to variations in the refraction of starlight as it passed through turbulent regions of the earth's atmosphere. But they were never able to establish the existence of a particular region or the exact meteorological conditions involved in the effect. An experiment by the Sandia Corp. of Albuquerque, N. Mex., reports Physicist Craig C. Hudson in Nature, has finally confirmed the occurrence of the twinkle layer in the outer atmosphere.

The Sandia scientists twice lofted beacon lights up to 65,000 ft. and allowed them to drift down by parachute through the part of the atmosphere that was suspected of causing twinkling. Each descent was continuously observed with a 16-in. tracking telescope equipped to record the scintillations. The scientists concluded that 80% of the high-frequency scintillation occurs in a layer of atmosphere about 5,000 ft. deep, at altitudes of between 30,000 ft. and 45,000 ft.

But why there? The question still has scientists stumped. The variations in the wind speed on the twinkling layer were no greater than in nearby regions. In a follow-up experiment now in progress, the scientists plan to make their next check on temperature and pressure fluctuations as possible causes of twinkling starlight.