Clyde Tombaugh sighting, Las Cruces

In August 1949 Clyde W. Tombaugh was already famous. In 1930 he had discovered Pluto. Now he was working at the White Sands Proving Ground and living in Las Cruces, New Mexico, with his wife, Patricia. By his own count he had spent several thousand hours watching the night sky.

August 20, 1949. About eleven o'clock at night, by Tombaugh's own account. He was in the backyard with Patricia and his mother-in-law. He happened to be looking at the zenith, "admiring the beautiful transparent sky of stars."

Then he spied "a geometrical group of faint bluish-green rectangles of light." Six to eight of them. The whole array took up about 1 degree of sky. The rectangles held fixed positions relative to each other, as if they belonged to one solid object. Patricia saw "a faint connecting glow across the structure."

There was no sound. The group moved south-southeasterly, growing smaller and dimmer, and faded out about 35 degrees above the horizon. Tombaugh watched it for about 3 seconds.

His wife caught it for about 1.5. It was too fast for an aircraft and too slow for a meteor. So faint that "had there been a full moon in the sky, I am sure they would not have been visible." "I was so unprepared for such a strange sight that I was really petrified with astonishment," he wrote to Richard Hall of NICAP on 10 September 1957.

The story went public on 7 April 1952, in LIFE's "Have We Visitors From Space?" Its version was different. LIFE dated the sighting to the summer of 1948. It described a solid oval "ship" with about half a dozen glowing "windows," moving south to north and trailing off "into a shapeless luminescence." It compared the object to the Chiles-Whitted case of 1948.

That June, J. Allen Hynek quietly surveyed astronomers at a convention for Project Blue Book. Tombaugh was one of five who reported sightings. He described Las Cruces and a later object over White Sands, and offered his telescopes to photograph UFOs if properly alerted. In January 1957 the Associated Press quoted him: "I have seen three objects in the last seven years which defied any explanation of known phenomenon, such as Venus, atmospheric optic, meteors or planes."

Donald Menzel, writing with Lyle Boyd in The World of Flying Saucers (1963), proposed that lit windows on a house had been reflected off an elevated temperature inversion layer. Tombaugh himself doubted any terrestrial reflection, because nothing of the kind had appeared before or since.

In 1968 atmospheric physicist James E. McDonald answered Menzel in a paper given in Montreal. He noted that Tombaugh had stressed the unprecedented transparency of the air that night. By his estimate an air layer could reflect at most about one ten-millionth of the light. Window glass reflects about 4%. The record of Tombaugh's own view is inconsistent, and some accounts say he later favoured atmospheric optics.

No photograph, film, radar return or physical trace exists. Only three witnesses and a few seconds of sky. But the witness was the astronomer who found Pluto, and case lists from NICAP to the Black Vault still count this among the sightings by astronomers that were never explained.