X Rays in the Unknown

The Geiger counters had been carried aloft in the nose of an Aerobee rocket, and when their records were recovered, scientists could hardly believe the data. If the figures were correct, there was an object up there in the constellation Scorpio that has yet to be spotted by the most sensitive optical or radio telescopes. That object is spewing out more X rays than had been calculated to come from all the rest of the billions of stars in the galaxy put together. But because they are unable to penetrate the earth's atmosphere, the rays remain invisible to instruments on the ground.

Wheeling with Stars. Physicist Riccardo Giacconi, who had planned the experiment along with Herbert Gursky and Frank Paolini of American Science & Engineering, Inc. in Cambridge, Mass., waited impatiently for the next X-ray measuring rocket. When that rocket was fired aloft last October, though, its instruments viewed another part of the sky; they did not record what was going on in Scorpio. They did report on two weaker X-ray sources, and their findings suggested that the original, strong X-ray source was probably located far out in space, beyond the reaches of the solar system, wheeling around the earth with the seasonal movements of the stars.

Last June a third rocket carried improved instruments above the atmosphere. Again they showed the X-ray source glowing powerfully in Scorpio. This time the scientists' report was much less guarded. There could be no doubt that something was there, but no one yet knows what it is.

Even before last June's confirming flight, other astronomers searched for the X-ray source with every possible technique, but they could not identify their target. Theories, however, are plentiful. Some astronomers believe that the X rays come from a very large concentration of stars near the center of the Milky Way galaxy that are otherwise invisible because of obscuring dust. Professor Bruno Rossi, M.I.T.'s cosmic-ray expert, doubts this idea because those stars would have to be producing more than 1,000 times as many X rays as the sun.

High Argument. Professor Philip Morrison of Cornell thinks the X rays may be generated when starlight picks up energy from high-speed electrons far out in space. Professor Minoru Oda of M.I.T. figures that the X rays come from a magnetic field surrounding the edges of the galactic nucleus. British Cosmologist Fred Hoyle suspects that they may be connected with the creation of new matter in the vast emptiness between the galaxies.

The high-level argument cannot get much farther until more is known about the X-ray sky. American Science & Engineering is already planning to fire rockets to look for X rays of longer wave length, and it has a contract totaling more than $1,000,000 with the National Aeronautics and Space Administration to put improved X-ray instruments on satellites. Other X-ray sources will probably be found, and Professor Rossi for one thinks that X-ray astronomy may eventually prove as important as radio astronomy. It may be that charged particles blown out of the sun knock soft X rays out of the moon, and if this were proved it would give vital information about the lunar surface, where astronauts may some day land. "There are things going on in space," says Dr. Rossi, "that are still unknown. That is what so excites us. We hope that by means of X rays we can detect some of these phenomena."

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