STELLAR GALAXIES

Taranaki Daily News, 26 November 1934, Page 6

STELLAR GALAXIES

EVIDENCE OF SUPER SYSTEM.

STATUS OF SPIRAL NEBULAE.

The remarkable extension in • human knowledge of what lies beyond the earth’s galaxy was discussed recently by the astronomical correspondent of the Manchester Guardian. Twenty years ago astronomers were uncertain whether the galaxy was the only galaxy or merely one. among others, he stated. The question hinged on the status of the so-called spiral nebulae. Were they true nebulae, component parts or dependants of the galaxy, or were they systems of stars, external . galaxies, situated at vast, almost inconceivable distances? The great lOOin. reflector at Mount Wilson, in the skilful hands of Dr. Hubble, settled the question once and for all about 10 years ago. It is now known that the so-called spiral nebulae are not nebulae but galaxies, and this is the name by which they are now coming to be known. Within the last 10 years much has been learned concerning, the external galaxies, their distances from the earth’s galaxy and from one another, and their distribution in space. Dr. Hubble, from a survey of 44,000 of these systems,, recently concluded that they are distributed throughout space more or less at random. Dr. Shapley, of Harvard,, however, has arrived at a different conclusion, and in a recent bulletin from Harvard College Observatory he announces that the distribution of the galaxies is markedly irregular' and that there is evidence of clustering in the region of the sky which he calls the northern galactic hemisphere. Dr. Shapley’s conclusion is definitely confirmed by an independent investigation by Mr. Bart J. Bok, a Dutch astronomer employed at Harvard, who concludes, after a careful study of the distribution of a large number of galaxies, that “different lines of evidence all indicate that the available. material points to the existence of a widespread non-uniformity in the distribution of external galaxies, and that this tendency toward clustering is probably one of the chief characteristics of the part of the universe within the reach of modem telescopes.” What does all this mean? It means that even as all the stars are irregularly distributed within the earth’s stellar system or galaxy, so the galaxies are themselves irregularly distributed within the universe. The sun is one of about 30,000,000,000 stars composing the known galaxy. Within the galaxy there is a well-marked region of condensation —the star clouds of Sagittarius, where the stars are much more numerous than _ in other parts of the system. This region of high stellar density is apparently the dynamical centre of the galaxy. If Dr. Shapley and Mr. Bok are correct in their recent conclusions the same law of distribution holds good .in the system of the galaxies, of which the earth’s galaxy is merely one component; and the region of higher density, which these recent investigations have revealed may well be a dynamical centre of the super-system round which the millions of galaxies, including our own, possibly revolve. This concept of a super-system whose members are separated, from one another by millions of light-years is a staggering one.