MEASUREMENT OF HEAT,

Waikato Times, Volume 108, Issue 18164, 31 October 1930, Page 3

MEASUREMENT OF HEAT,

FROM UNNAMED STAR. AN IMPRESSIVE EXPLOIT. WASHINGTON, September 20. Measurement of the heat from an unnamed star 631 times fainter than the faintest star visible to the unaided eye was announced by the Carnegie Inst’tution. ! The tiny heat ray, one of unnumbered thousands whose existence has been ■ suspected but not hitherto so definitely established, was caught by an instrument weighing one-thousandth as much as a drop, of water, named a ; thermocouple. ■ The unnamed star is of the thirj teenth magnitude. The temperature 1 of its ray Is described in the' an- ; nouncement only indirectly by a com- , parison, which states: — I “This exploit. becomes even more impressive when it is realised that a ! star of the sixth' magnitude, that is, j one which can barely be seen with the unaided eye, radiates upon the whole United States no more heat than the sun radiates upon one square yard |of surface. Yet, in the case of such 1 a star, the thermocouple will show ! that the increase in heat on account of : It is one-half of one milHonth of a , degree Fahrenheit and' that the elec- ] trie current generated thereby is about one twenty-billionth of an ampere. “This value becomes Intelligible in consideration of the fact that, the light In an ordinary Incandescent house light is produced by a current of from one- ' fourth to one ampere. i i Extreme Sensitiveness. ! i "The extreme sensitiveness of the i thermocouple is again illustrated in the case of stars as they rise above ; the horizon. The higher they ascend : the brighter they appear, because the ! higher they rise the less of earth’s at- | mosphere their rays are obiged * to | penetrate and consequenty the less their rays are absorbed, j “The sensitivity of the thermocouple is so great that with bright stars near the horizon the change- in brightness : which takes place in one minute of • time can be detected.” ! The thermocouple is only two hair- ; like wires welded together at their "ends, one of bismuth and the other of .bismuth and tin. This union of un- ; like elements changes almost infinitesimal amounts of heat into electrical ■ current 1 which can be measured. An eye-piece permits of focusing the thermocouple so that ony the rays of the star to be measured fall on the wires. This instrument was perfected by Dr. Edison Rettit and Dr. Seth B. Nicholson of the staff on Mount Wilson Observatory of Carnegie Institution. ~ With it the surface'temperature of the hottest stars is found to be il,ooo degrees Farenheit and 2,800 for the coolest. The hottest stars are blue and the coolest red. Among the planI ets Mercury’s temperature is found to be 800 degrees, that of the cloudtops hiding the face of Venus 9 below zero, Mars much like that of the earth’s and Jupiter’s face 216 degrees below zero.