The Coconino sun., 1921-10-21
MEASURE THE HEAT
 FROM THE STARS AT
 LOWELL OBSERVATORY

LUWELL UDDENVAlUN Dr. w. w. Coblentz, physicist in the
 United States bureau of standards of
 Washington, D. C., spent the past
 month at Lowell observatory measur-
 ing the radiation of heat from the
 stars. Exteremely delicate and sens
 itive instruments consisting of so- called "thermo-couples" and special ly constructed galvanometer were used in connection with the great 40- inch Lowell reflecting telescope. Dr.
 CoblentZ gave an informal lecture at the observatory in which he described the instruments and methods of obser- vation, and gave historical account of the development in the improve ment and refinement of these import ant methods of scientific research. By his own great skill and patient labors extending over many years he has succeeded in bring his apparatus to such a high degree of perfection that he obtained results far beyond any thing previously obtained.
 A thermo-couple consists of a june ton of two dissimilar metals, as for example, bismuth and antimony, which has the property that when a small amount of heat falls upon the place where the two metals are joined to- gether a feeble current of electricity will be momentarily generated and which can be detected by a suitable galvanometer, an instrument general ly used for measuring weak electric currents. The galvanometer used in the present work is so sensitive that it will indicate the flow of current of electricity of 1-10,000, 000,000 of an ampere. The tiny and delicate thermo- couple, parts of which are built up out of hairlike filaments of about 1-1000 of an inch in diameter, was held in small glass receptacle from which the air had been exhausted in order to increase the sensitiveness. In practice the thermo-couple is placed in the focus of the great mirror of the telescope so that the image of the star to be studied falls upon the thermo-couple and then the amount of heat is measured by the reading of the sensitive galvanometer. The sensitive nesss of the apparatus is such that when used in connection with the pow erful mirror of the Lowell refecting telescope the heat from candle placed at a distance of 55 miles could be detected.
 The lecturer described his method of analyzing the total radiation of a star into it's component parts. He has tabulated the results of his ob- servations here of several of the brighter and well-known stars and the marked difference in the amo,int and character of the total radiation from the various objects was very cvi- dent. For example, there isia strik- ing difference in ihe amount of heat sent out by, say, bluish-white and orange colored stars such as Vega and Arcturus, two of the bright stars now visible in the evening sky. These stars are of nearly the same apparent brightness to the eye but the one of the ruddy tint gives out more than two times as much heat. For still redder stars the quantity of heat ra- diated is approximately increased as shown by the observations.
 The heat from the stars received at the earth is almost inconceivably small when measured in terms of our cus- tomary standards of everyday experi- ence. The following example given by Dr. Coblentz will illustrate how excessively small are the quantities of heat that come from the distant lum- inaries about us. The heat from the north pole star is readily measured with his instruments when used with a powerful telescope. If the heat of this star fell continuously upon a square centimeter Slightly over 1-17 of square inch) of surface it would require one million years to raise one gram (about 1-2000 of a pound, or a small cube of water measuring about 4-10 of an inch along each edge) one degree centigrade, assuming that, in the meantinme, no heat is lost but that all is effective in warming the water. In contrast with this value the radiation of the sun which falls upon the same area is sufficient to raise the temperature of the gram of water one degree in about one minute. Thus it can hardly be expected that the heat energy radiated by the mil lions of stars can be looked to as our source of supply for mans needs. Yet one star---our sun--is capable of SUD- plying the earth with such abundant radiation because of its nearness. From the short period of time that reliable data have been gathered of the radiation of our sun it is quite inn possible to predict what the future store of the suns energy may be, but we may learn what the future holds in store for us by careful study of the planets of our system and of the stars in their various stages of de- velopment.
 Dr. Coblentz left for Washington the day following the lecture.