A Glimpse Into Limbo

It was only a blurred dot on a photographic plate. But as displayed last week by Astronomer Rudolph Minkowski of California's Mount Wilson and Palomar observatories, it was a scientific milestone: the dot, probably the collision of two galaxies 6 billion light years away from earth, represented the most distant phenomenon ever identified by man.

The picture, taken by Minkowski with Palomar's giant 200-in. Hale telescope, was a dramatic symbol of a surge in astronomical science made possible by a far-sighted alliance between optical and radio telescopy. When Palomar's 200-incher was completed in 1948, no one expected it to photograph galaxies more than i billion light years away. A major reason: in such telescopes the field of view is very small, and to reach full range they must take long-exposure pictures of each tiny spot before moving on to the next. Thus, Palomar cannot range the heavens at random, looking for extra-big galaxies that can be photographed at incredible distances. It must be told where to look.

"Radio Stars." The new radio telescopes furnish just such vital guidance. They can sweep the sky, detecting waves coming from "radio stars"--often galaxies which are in collision and generating enormous amounts of radio energy.

Ten years ago radio astronomers at the University of Cambridge reported waves from a dim radio star in the Bootes constellation. Radio astronomy was then too crude to give accurate directions--and when Minkowski tried to photograph the phenomenon with Palomar's telescope, he found nothing. But new radio telescopes at Cambridge and in Owens Valley, Calif, recently drew an accurate bead on the radio star in Bootes. Minkowski pointed the Palomar telescope at the spot indicated. And after exposing a photographic plate for two hours, he got his picture of two big galaxies in collision.

Tale of a Spectrum. Minkowski still did not know the distance from earth of the colliding galaxies. Further exposures, up to nine hours long, gave photographs of their spectrum. The familiar spectral lines had shifted far into the red. According to the theory of the expanding universe, a red shift means that the photographed object is moving away from the observer with a speed proportionate to the shift. In this case the galaxies appeared to be receding at the extraordinary speed of 90,000 miles per second--about 46% of the speed of light which, according to Einstein, is the ultimate velocity.

Since the distance, in turn, is proportionate to the speed, what Rudolph Minkowski got was a photographic glimpse of something 6 billion light years away--and 6 billion years ago--probably before the earth or its sun were formed. During the past 6 billion years, the galaxies may have accelerated to almost the speed of light. If so, they have passed over the brink of the theoretically visible universe and entered a sort of limbo which cosmologists visualize only vaguely.

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