CLUE TO GALAXIES IS IN CEPHEID VARIABLES

CEPHEID DISTRIBUTION MAY BE GRAVITATIONAL INDICATOR

The Cepheid variable stars, whose fluctuating light beams enable measurement of great interstellar distances, may prove also to hold important new clues to forces at work within the great island universes, or galaxies like our own Milky Way, Harlow Shapley, Director of the Observatory, recently told the National Academy of Sciences.

Star photographs made at the Harvard astronomy station in South Africa reveal an unusual distribution of Cepheid variable stars in the Small Magellanic Cloud, neighbor star system of the Milky Way. There is a "peculiar concentration" of the larger, longer-period Cepheid variable stars in regions where the star population is dense, Shapley said. Cepheids fluctuate in brightness in periods ranging from a few hours to about fifty days; their mass is four to five times that of the Sun.

Shapley said that the "newly found prenomenon" of Cepheid distribution may prove to be "an indicator of gravitational potential throughout a galaxy." However, there may be another, alternative explanation of the peculiar distribution, involving the distribution of various chemical substances in the Magellanic Cloud, Shapley said. There is a possibility that the chemical distribution of the cloud is such that the large stars were found in densely populated star areas.

Shapley's report to the Academy dealt principally with observations of southern galaxies and clusters, and was given in collaboration with Dr. John S. Paraskevopoulus, Superintendent of the South African station.

Among the newly discovered objects reported were two spiral nebulae, un-usual in that they possess no concentrated nuclei; and a Magellanic Cloud in the constellation Cetus, a new member of a class of irregularly shaped, conglomerate stellar systems.