Fred L. Whipple, Professor of Astronomy, last Sunday announced a new theory on the twilight glow that appears after subset. Whipple attributed the so called zodiacal light to particles of cosmic dust in space.
Reporting to the Observatory's Visiting Committee, Whipple said the glow occurs when icy surfaces of the particles are vaporized by the sun.
The dust is thrown from comets and circles the sun in their orbits. The pieces range from the size of marbles to that of pin-points. If one is heavy enough, the gravitational pull of Jupiter draws it from its path; otherwise it spirals slowly into the sun.
30 Tons a Second
Whipple estimates that 30 tons of dust are pulled from comets every second. One ton per second would be enough to maintain the zodiacal glow indefinitely.
He added that this same material, by scattering the light from the sun at the time of a total solar eclipse, contributes to the brightness of the corona--the ring or light remaining when the sun is completely blocked by the moon.
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