VOGEL OF POTSDAM.

New Zealand Times, Volume XXIX, Issue 6362, 9 November 1907, Page 12

VOGEL OF POTSDAM.

The death of Professor H. C. Vogel, who in 187*4 organised and has since directed th© Observatory at Potsdam, removes au important figure. _ Professor Vogel’s scientific life coincided with the development of th© spectroscope and its application, to tho problems of stellar research. H© was, in fact, on© of the chief makers of tho new astronomy, and Potsdam was the first purely astrophysical institution in the world. It is not much more than 60 years since Bessel declared that the old astronomy was tho only astronomy, and Comte regretted wo could never loam the composition of tho 'stars. Very early in its career the spectroscope changed oil that, and in tho hands of men like Vogel began to perform wonders no ou© had dreamed of promising. Vogel early seized tho fact that the spectrum was an index to stellar ©volution, ’and h© prepared a spectrum catalogue of 4051 stars. It is by such means it has proved possible—m the hands of a Sir Norman Lockycr—to trace the life history of. a star from the cradle to the grave. was next one of the first to detect and discuss tho peculiarities of planetary spectra. Shining by reflected light these would of coureo givo the solar spectrum were it not for absorption in their atmospheres; and conversely any changes in it must be due to this cause. In this way the atmosphere of Mare would appear to possess water vapour, and that of Jupiter and Saturn some absorbing vapour unknown to ours. The same dark absorption band and several others are shown by Venus and Neptune. Turned upon comets the spectroscope reveals the changes in their physical, condition as they near the eun; tlio linos of carbon, eodium, and iron, for instance, flashing out as their temperature rises. But Vogel soon began to apply the instrument in unheard of ways. The solar spectrum is full of dark lines, named after- their discoverer, Fraunhofer, due to absorption in the atmoinhere of the sun, for gases absorb the same kind of radiation as they give out. W© know, however, that th© sun is rotating on its axis, and by re-ason of that those lines should undergo displacement. This effect Vogel predicted and worked out, jvnd went on to his greatest achievement—the investigation of star motion in the line of sight. Such motion, of course, cannot bo delected in a telescope, but the spectroscope reveals it by a shift in the position of the lines, from which the actual amount of motion can be calculated. One immediate and drar matic result of this advance was th© resolution of variable stars of th© Algol type into double stars. They were too close to one another and too far away for the best telescopes to reveal their complexity; but the vagaries of their spectra did so* and gave th© astronomer th© previously unknown class of spectroscopic binaries. In this field Vogel turned possibilities into precision; and though Potsdam has now many rivals, especially in America, it is impossible , to over-estimate the splendid pioneering accomplished by Vogel.