In The Milky Way, A Monster Fountain Of Antimatter?

Gamma Ray Observatory Reports From Space


WILLIAMSBURG, Va. -- Astrophysicists announced yesterday that they have discovered what appears to be a monster fountain of antimatter erupting outward from the core of the Milky Way.

They said the discovery would compel them to alter their image of the disk-shaped galaxy. In the revised image, it is as if a burst of steam were spurting upward from the yolk of a fried egg.

The discovery, reported at a meeting in Williamsburg, was made using the Compton Gamma Ray Observatory, a satellite launched by the National Aeronautics and Space Administration six years ago. The four instruments aboard the observatory detect, measure and record gamma rays: invisible rays that have higher energies than all other forms of radiation, including X-rays.

The antimatter was discovered as a result of a series of observations made by the satellite since last November.

Antimatter -- particles of which are exactly like their ordinary matter counterparts, except that they carry opposite electrical charges -- cannot be directly detected in space. But when antimatter comes into contact with ordinary matter, the two kinds of matter instantly annihilate each other, producing gamma rays, which can be detected by instruments outside Earth's shielding atmosphere.

The newly discovered plume of antimatter rises some 3,500 light-years above the disk of Earth's galaxy, which is about 100,000 light-years across. But even if this cloud of antimatter were to reach Earth, the scientists reassured their audience, it would cause no harm, because the concentration of antimatter particles in the cloud are extremely diffuse.

Moreover, only positrons -- positive electrons -- are believed to be present, not antiprotons or entire antimatter atoms. Although forms of antimatter other than positrons have been created by laboratories on Earth, they have never been unequivocally identified elsewhere.

A prevailing theory is that the Big Bang of creation produced approximately equal amounts of matter and antimatter, which promptly annihilated each other, but that a small excess of ordinary matter was enough to create the universe as we know it, with very little surviving antimatter.

Astrophysicists representing the Naval Research Laboratory, Northwestern University and the University of California at Berkeley, who collaborated in the discovery announced yesterday, said the cause and the nature of the antimatter fountain were puzzling. It might be a more or less continuous shaft of antimatter streaking northward from the galactic center, or it might be a cloud, separated from the main part of the galaxy.

Dr. Charles Dermer of the Naval Research Laboratory surmised that the fountain might be a mixture of gas, boiling away from violently dying stars near the center of the galaxy, and a stream of positrons.

It has long been known that Earth's galaxy looks something like a fried egg with pinwheel spirals. Earth lies in one of these spirals, and as we look up at the Milky Way on clear nights, we look inward toward the galactic center. But dust and gas obstruct any light from the galactic center, and so astronomers depend on other types of radiation to deduce the galaxy's innermost structure.

Pub Date: 4/29/97

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