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75, 50 & 25 years ago.

September 1937

The Real Corona "The first definite proof that the solar corona is not made up chiefly of flaming coronal streamers alone, as has been supposed, but is an even, globular blanket covering the sun more than a million miles deep, was revealed [August 12] by a conference of astronomers at Harvard Observatory.

"Photographs leading to this finding were taken from an airplane in the substratosphere off the coast of Peru during the eclipse of last June 8."

Astronomers had expected airborne equipment to reveal more delicate tracery in the corona than is seen from the ground. Instead, it made the general glow stand out.

September 1962

One Odd Comet "The general rule that comets far from the sun are faint, quiescent, and nearly structureless objects has been dramatically violated by Comet Humason (1961e). ...

"Sudden and striking changes in appearance, often in less than a day, have added to the great interest Comet Humason has aroused among professional astronomers. To record these alterations, the 40-inch reflector of the U.S. Naval Observatory is especially effective. Elizabeth Roemer writes ... 'I think the corkscrew feature in the tail on July 7th is real.'"

Then shining at 8th magnitude from well outside Mars's orbit, this peculiar comet remains in a class of its own.

September 1987

Still No Planet X "The twin Pioneer 10 and 11 spacecraft have found no evidence for a planet beyond the orbit of Pluto. ... [P]recise tracking data indicate that neither probe has felt the gravitational pull of an unseen body while racing through the outer solar system. ...

"[A]pparently reliable 19th-century observations of Uranus and Neptune show that their orbits were slightly erratic. ... Pluto and its moon aren't massive enough to have shifted Uranus and Neptune by the amounts seen. But if a larger planet [than Pluto] were responsible, why didn't it affect the Pioneers?

Those 19th-century observations weren't so reliable: subtle flaws mimicked a Planet X's effect.

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Author:Sinnott, Roger W.
Publication:Sky & Telescope
Geographic Code:1USA
Date:Sep 1, 2012
Words:322
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