STARS DISTANCES

Bay of Plenty Beacon, Volume 5, Issue 20, 23 February 1942, Page 2

STARS DISTANCES

METHODS OF MEASURING GREAT PROGRESS IN CENTURY "A. hundred years have passed since Bessel and Henderson announced that the gulf separating the solar system from the stars had at last been spanned," writes the astronomical correspondent of the Manchester Guardian. , "To. have measured distances up to sixty billion miles was regarded as an awe-inspiring achievement. "To-day, a century later. stars placed at such distances are regarded as near at hand. Thousands- oT parallaxes have-since been measured by the trigonometrical method, generally by photography:, but the system of Alpha Centauri at twentyfive billion miles, or four lightyears. remains the nearest system. "For Prexima, the tiny star with slightly greater parallak and therefore smaller distance, is physically connected with the stars of Alpha Centauri. "In recent years other methods of measuring stellar parallaxes have he-en devised, and in consequence the distances of distant stars, starclusters, and external galaxies have been determined. "There is a spectroscopic method, a method based on the 'period-lum-inosity law' of the variable stars known as Cephcids, and a method based on the apparent magnitudes of distant objects. "A hundred years ago astronomers were congratulating themselves on having sent their sounding line out into inter-stellar space to a distance of ten light-years; to-day the sounding line has been sent out not only into inter-stellar space but into <nter-galactic spacc: the ' greatest measured distance in the cosmos is that of a faint external glaxy five hundred millions light-years away."