Science: Waves from Space

One of astronomy’s deepest mysteries is the “radio star,” an object in space that “shines” with radio waves instead of with .visible light. The first radio stars were discovered only about two years ago, but already more than 100 have been plotted on the sky maps. They occupy positions which do not correspond to any visible stars. Astronomers do not know what they are or how they send out their waves.

In last week’s Nature magazine, R. Hanbury Brown and C. Hazard of Britain’s University of Manchester announced that they had detected radio stars in M. 31, the great spiral nebula in Andromeda, 750,000 light-years from the earth. They did the job with the largest radio telescope (a trellis-like “dish” of wires) at Jodrell Bank Experimental Station south of Manchester. Normally this telescope points upward, receiving radio waves from a narrow “beam” directly overhead. If the mast at the center is swung 14° to one side, the telescope points, in effect, toward the Andromeda nebula.

Extra-sensitive equipment was necessary, and the radio astronomers had to wait for still, rainless nights, though radio reception from the stars is not ordinarily affected by the weather. Six times they allowed the rotation of the earth to sweep the telescope past the nebula. Each time they moved the mast slightly to cover a different strip of sky. In the four middle sweeps they found what they were looking for: low peaks in the curves representing radio energy reaching the telescope. Careful analysis of the curves showed that the waves must have come from an oval object like the Andromeda nebula seen with visible light.

To check their results, the astronomers calculated how much radio energy is sent out by the Milky Way galaxy, another vast swirl of billions of stars, of which the sun is a part. Then they calculated what this radio source would look like to their radio telescope if it were as far away as the Andromeda nebula. The calculations showed that it would look much the same. This went far to prove what astronomers had long suspected: the Milky Way galaxy is a “twin” of M. 31.

The radio waves from Andromeda proved also that radio stars are not peculiar to the “local” galaxy, i.e., the Milky Way. They are probably common in all , the galaxies scattered through the depths of space. Dr. A. C. B. Lovell, head of Jodrell Bank, suspects that they are just as numerous as the visible stars. They may be stars being formed, he speculates, out of interstellar gas. They may be dying stars (black dwarfs) too cool to shed visible light. Or they may be something new and still undreamed of by astronomers.