CENSUS OF STARS

Evening Post, Volume CXXV, Issue 146, 23 June 1938, Page 17

CENSUS OF STARS

YAST TASK COMPLETE

;AID FOR ASTRONOMERS All the stars the eye can count ore Indexed, writes E. S. Grew in the "Observer." They are fewer than 10,000. The stars a small, telescope b:*ngs into the field of vision are classified in the same way, and the total is thus brought up to 33,000. This is one way of recording the completion of one of the most comprehensive tasks of astronomical observation of our time, the New General Catalogue of Stats, which was begun by Lewis Boss, of Albany, 35 years ago, and has been carried on by Benjamin, his son. There are many star catalogues, 238 individual ones, since Bradley published the first great survey in 1755, followed by those of such masters as Piazzi, Bessel, Lalande, and Struve. , They are indispensable for any knowledge of the movement of a star, because the current catalogue will show by comparison with a predecessor, how the star has moved in the interval between the publications. But because some of the catalogues were out of date before they were published, and few noted the positions of the stars on the same system, consultation of them imposes a weary task of comparison on the astronomer. COMPLETED CATALOGUE. The Boss completed catalogue collects all the observations of its predecessors, better or. worse, reviews them, corrects them, and considerably augments them, while reducing the star positions to"a common system. Lewis Boss lived to publish in 1910 the description of 6188 of the brighter stars. His son worked at the same laborious, task, to offer, rather more than a quarter of a century later, the positions and characteristics of 33,342 stars brighter than the seventh magnitude, to the service of astronomy. Their plaees, types, and proper motions are all specified in the .1300 pages of four crowded quartos. The quality of the slave labour needed to produce the catalogue only an astronomer can gauge. Every star as it passes the micrometer wire of the big transit telescope has to be timed and retimed over and over again to the thousandth of a second. The most experienced observers must be employed, their observational idiosyncrasies corrected by a theory of errors. Even their meals may be regulated on a night of observation, to prevent the disturbance of their personal equation. The result is 33 t 342 stars defined as accurately as human observation can compass. This corps of picked stars is only a fragment of the army of many millions undescribed, perhaps never to be ■> described, but by the known the astronomer may arrive at the disposition of the unknown. They form what Einstein would call a frame of reference, though, according to his standards, It is' far from being a fixed one, by which the movements of other celestial objects can be measured. THE SUN "DETHRONED." If not fixed stars, they are as near to being fixed as we can get. They enable usi for example, to state the position of such a star as our sun in the Milky Way; to determine its path and its speed along it; or to guess at the movement of the Milky Way itself. To some of Euch.celestial conundrums answers have already been suggested. For example,-the sun, once authoritatively placed at or near the centre of the Milky Way, has been dethroned from, that .Olympian; altitude to become a mere suburban star. According to tne latest computation, it is some 32,000,000 light-years away from the centre. ■ But in the last twenty-five years the stated distance has fluctuated between 50,000,000 and 20,000,000 lightyears. These and other discrepancies of calculation why this new Court of Appeal 6f the Boss catalogue stars is wanted.,,. The same Court may give more authoritative decisions on the part of the sun, which seems to be travelling, with other companions, towards the constellation of Sagittarius, the Archer,; whose bow is bent low down in our northern skies. It may tell us more decisively that the Milky Way is rotating, carrying the sun round with it on a journey of 200,000,000 years. All Such assertions can be verified or corrected only by such an instrument as this New Catalogue. It furnishes, by its stars, reference points known to this generation, and because their movements are also certified will be surely found in known positions a generation hence. There are many problems for them to clear up. , The Star Clusters are one of them. MIGRATING STARS. When Lewis Boss began his work he was greatly, interested in Migrating Stars, to which order it seemed our sun might belong. They fly like birds, in flocks, seeming to ignore the general movement of other stars about them. What might be distinguished as a flight of birds overhead would become, with increasing distance, a cloud, a wisp, a smudge in the sky, and at last a point. So it might be with the migrating stars; and if the process were reversed a dimpled, fuzzy ball in the sky might, as it drew nearer in many millions of years, resolve itself into star migrants, There are-such fuzzy balls in the heavens. They are among the most distant objects of the Milky Way and are the Globular Clusters. About the time Boss began his catalogue a discovery at Harvard put the astronomers on the track of the typical Hercules Cluster, which was found not-to be a fuzzy star but a collection of 35,000 suns, many a thousand times as bright as our own. It is not the largest cluster—there are ninety-four others; but no more have ever been found. , Spiral nebulae may be discovered by the thousand, but the globular clusters are;'a family as exclusive as singular. They? are confined to one half of the sky, and a quarter of their number are in a star cloud of that same constellation'of Sagittarius, to which our own sun'spath is directed. They form 'one of the problems awaiting further elucidation. Women sent to prison in Britain during a recent period of 12 months numbered 3869; of this total more than half were penalised because they could not pay debts or fines.