Nebular Knowledge

On a long-exposure plate Mt. Wilson Observatory's Edwin Powell Hubble lately found a streak of light which was subsequently identified by other telescope men as an asteroid, one of some 1,400 small planets between Mars and Jupiter. It was a remarkable asteroid in that its orbit was more steeply inclined (39DEG) to the general plane of planetary revolution than any other except one (43DEG). But it seemed odd for Dr. Hubble, of all astronomers, to be making such a discovery, for the realm in which he usually works is so distant that the asteroids by comparison are practically underfoot. He just happened to catch the little planet, in fact, while he was photographing an island universe of stars hundreds of millions of light years from Earth.*

In New Haven, Conn. last week Edwin Hubble delivered the first three of eight endowed lectures on the present state of nebular knowledge, free to Yale students and townsfolk. He wasted no time whizzing his hearers past the solar system, past the local star cluster, past the local star galaxy (the Milky Way) to the limits of the known universe. Dr. Hubble's longest looks into space have disclosed star-swarms 500,000,000 light-years away, and this appears to be the limit of Mt. Wilson's giant telescope. Thus the observable universe is a sphere about a billion light-years across. What Dr. Hubble calls a "preliminary reconnaissance" shows that the sphere probably contains 100,000,000 nebulae composed of stars, the average nebula being about 20,000,000,000 times as heavy as the Sun and shedding 85,000,000 times as much light.

Few years ago Harvard's chaos-hating Harlow Shapley was mildly disturbed by what appeared to be a lopsided condition of the universe. The star galaxies seemed to be unevenly distributed in space, more in the northern sky than in the southern. This, however, turned out to be only a small-scale irregularity, tended to disappear when larger sky areas were polled, deeper penetrations into space made, the obscuring effect of dark matter allowed for. Now the galactic distribution in the observable sphere approaches uniformity. Dr. Hubble last week compared the population density to tennis balls 50 ft. apart. This he believes represents a dependable sample of the universe beyond the visible limits. The actual limits may never be reached except in the unlikely event that an instrument is built to see all around the curved space of Relativity.

* One light-year = approximately six trillion miles.

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