New Cluster of Stars Discovered By Camera of Harvard Observers

Harvard astronomers have discovered a gigantic cluster of stars in the southern sky, which apparently belongs to no known class of cosmic systems, and which may thus reveal the existence of an entirely new group of star systems in the universe, it was reported today in the Harvard Observatory Bulletin by Harlow Shapley, director of the observatory.

The star-island, shaped like a football, is located in the southern constellation, Sculptor. Its light is so faint that the individual star members can be detected only through very powerful telescopes.

Thousands of Stars

Despite its vast size, including thousands of individual stars, and stretching out 2 degrees in the sky, the group has never before been seen by astronomers because of its faintness, Shapley said.

Although they have been able to count the thousands of stars now visible in the group, the astronomers have been unable as yet to measure its distance and size, and these characteristics must be known before the object can be properly classified. Before accurate definition of the group is possible, the observers must find within it some variable stars, whose period and brightness can be used to determine the distance and dimensions of the body, it was explained.

Photographed in South Africa

Disclosure of the group was a matter of good fortune, depending on the fact that an abnormally sensitive photographic plate chanced to be focused on Sculptor on a very clear night. The photograph on which the system was found was taken at the Harvard astronomical observatory at Bloemfontein, South Africa.

From their star-counts, involving an extremely difficult enumeration of a mass of tiny specks on a photographic place, the Harvard astronomers estimate that there are about 10,000 objects in the cluster between the brightest stars, about 18th magnitude, and the dimmest that have yet been counted, about 19.5 magnitude. How many stars there are fainter than this has not yet been estimated.

250,000 Light Years Away

Of conjectures advanced as to the probable nature of the cluster, Shapley said the evidence so far favors the assumption that the stars may have an absolute magnitude of -1.5, comparable to that of the brightest stars in the globular star clusters. If that is the case, it can be definitely established only when variable stars have been found in the group, then the cluster would be about 250,000 light years from the earth, and would measure about 6,500 light years in diameter.

For any assumptions, however, the Sculptor cluster is sufficiently different from any other known star systems to warrant the belief that it represents a hitherto undisclosed classification, Dr. Shapley said.

Ignored on Previous Photographs

A check through the Harvard library of star photographs revealed that the group appeared also on long-exposure plates made in 1908, but only as a very faint patch of light, doubtlessly mistaken by the observers for general background unevenness or a faint blotch in the photographic emulsion.