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$ SR % S o m oo m n on t i t 11 on n t n Un UR 0NE 1 OR UU U e WAE ETeE ANNIANINU e A few years later the University of Chicago was| about to start a great new observatory, with the world's largest telescope. using funds provided by Charle T. Yerkes. Dr. Hale was selected to organize and serve as first director of this ngw world-- famous Yerkes Observatory. As a result of his success there, when the Carnegie Institution, in 1904, decided to found a great observatory chiefly ftor the study of the sun, Dr., Hale was again selected as the organizer and first director. From this has arisen the great Mt. Wilson observatory, perhaps the best--known in the world, and with the largest telescope. When the World War came, Dr. Hale's organizing abilities again served in good stead, in the formation of the Council for l\}ational Defense, now the National Research Countil, which is the central body for the organization of scientific research throughout the country. -- Largely due to his unceasing labors during the| war, his health broke down after the conflict was over, and jfinally he had to retire as director of the Mt. Wilson observatory. He was made it\s'honoury director. UT even retirement could not stop such an active brain, B and in recent years he has continued to assist astronomical work in many ways. * The announcement was recently made in the papers that a new astronomical telescope, with a mirror 200 inches in diameter. four times the area of the present champion at Mt.. Wilson, was to be made for the Caliz)mia Institute 'of Technology, close peighbor of the Mr. Wilson observatory at Pasadena. 't was announced that the International Educattn Board would provide the funds, running well into the millions. But the name of the man who has successfully brought this project to culmination was almest overlooked. That name was &orge Ellery Hale. Now active design of the new telescope has be-- ANLH NOANHECHEITTH aking Movies of the HININHIH {[VIH "HLRILNItN gun. and still his is the guiding spirit behind it. Dr. Hale's private laboratory and observatory in Pasadena is the scene of the invention of the * spectrohelioscope, with which it is possible' to see "movies" of the sun Dr Hale Everyone knows how a prism breaks up a beam 2o2 . wou of white light into its component colors and forms sct an arn a spectrum.. Not quite so many people know that astronom the same thing is done by a pieee of polished metal on which are ruled fine lwes, thousands to the inch. The astronomer calls this a diffraction grating, or simply a grating. When the light from the spun is passed through a nartow slit, then through the proper lenses to a grating or prism, and the re-- sultant beam of colored light is examined by other lenses, the colored spectrum is seen, crossed by numerous dark lines. If this same combination of prisms and lenses--which is called a spectroscope--is used to examine the light from white hot metal, such as the fhlament of an electric light, the colored spec-- trum appears, but the dark lines are absent, This is called a continuous spectrum. _ _ &® Still a third kind can be obtained from the bright yellow light that appears when a pinch of salt is dropped into the blue flame of a gas range. The speclrox{opc shows this yellow light from salt to consist only of yellow. ' Its spectrum is merely a pair of bright yellow lines, very close together, against a black back-- ground. It is called a bright line spectrum, and is due to the glowing vapor of sodium, one of the two elements that make up ordinary table salt . Potassium, present in caustic potash, gives a bright vidlet line, and the different elements have their own character-- istic bright line spectrum. UPPOSE. now that you have a spectroscope and are look: q ing at the spectrum of the sun and the sodium light at the ~*_ same time. and have it arranged so that the two spectra are side by side. Then it will be found that in the yellaw part of the solar spectrum there are two dark lines, and that these exactly coincide w;itl} lh'e two brig_ht ye"o_yv-lim:g of the sodium spectrum. If the light from an electric light filament is passed through a flame of burning sodium, the same 'two dark lines appear. This shows that glowing sodium vapor not only gives off yellow light of its own, but that when brilliant white Tight. consisting of all the colors, is passed through it, the same pa}T;-f' tl;;;:li;; light is removed. . (Copyright, 1929 a 4 iicucd t t mt td «TLA e=UL EO CTET TTA UITTTIUUTC TY 11-- light, consisting _ This was the principle first used to reyeal the prominences art of the yellow _ 'without an eclipse. By passing the light from the edge of the sun, where the prominences are best seen, through a spectroscope NEA Magazine and Science Service--Printed in U. 8. A.) . _. would UX ' C T t an army of ustronomers to matching the sun With the sodium light the case is different. The two lines are seen through a small instrument at just about the same brilliance as with a large one, though farther apart. _ The reason for this is that the sodium light is entirely of a single color--yellow. The spectroscope breaks light composed of several colors into bands of each; light already consisting of a single color cannot be broken farther. RINNWIINTHINIO® HOUGH prominences of the sun are frequently occurring, T they are invisible to the unaided eye, or even when one looks through a telescope equipped with the darkening equipment that makes looking at the gun a safe pastime. The reason for this is that prominences are so much fainter than the bright back-- ground. During a total eclipse, the moon just covers the bright area of the sun, and then, if there are any prominences they will be easily seen. . -- I _ But there is another way of seeing them, and one does not need an eclipse to do it. If the light from an incandescent lamp, that gives a continuous spectrum, is passed through a powerful spectroscope, the spectrum is spread out much more than with a smaller instrument. As the same amount of light must cover a much larger area., the spectrum through a large spectroscope is much fainter than through a smaller one, if the light source is the same in each case. Sometimes the radiation of light from one part of the inner layer may increase, and the glowing gases of the chromosphere may be thrown outwards for great distances--even to half a million miles or more. _ When this takes place, you have what is called a prominence. to matching the sun. This outer layer is called the chromosphere. Ordinarily it is in a | rather quiescent state. Gravity, of the great solar mass, tries to pull it inwards, but there is so much light leaving the sun, that it exerts a pressure outwards, the two practically compensating for each other. es dammil [ 10 14» e EB U NUE TAE NU CCE CE mt EUn N TN TR C i®®s o o e it t «t tE U ELN EN NR LE e um un o un L ie aiun : @@ee So much has the spectrohelioscope--with the sun telescope to go with it--been simplified, that it is now being manufactured for a cost no greater than that of a small automobile. Anyone with a little mechanical skill can make one at a cost comparable with that of a good radio set. Now Dr. Hale is interested in getting a great body of amateur astronomers at work with such instruments so that someone will be sure to be watching the sun at every moment. However, it has. one disadvantage. An exposure may take several minutes. The astronomer cannot watch the sun while he is taking it, and so he has to shoot more or less blindly. There may be something interesting happening on the sun at the time, or again there may not be. What was needed was a method of actually watching the sun in the light of a single wavelength. To do this, Dr. Hale invented the spectrohelioscope, the name of which simply means that it is an instrument to see the sun with the aid of its spectrum. In this device, the two slits oscillate back and forth so rapidly that when the astronomer looks at the second slit through an eyepiece, he sees a large area of the sun. It can be arranged to show the entire sun at once, but in its usual form, it only shows a piece of it, on a larger scale than could be seen with the whole solar disc. An explanatory photograph of the specirohelioscope . . . and --below the photograph--a diagram showing how the imven-- tion enables observers to analyze the sun's flaming surface. HIS is the spectroheliograph, first great invention of Dr. T Hale. It has been used constantly at a great number of observatories in the last 30 years, and a large amount of our present knowledge of the sun has come from it. -- Instead of looking at it with the eye. you place a photo-- graphic plate right in back of the second slit, and so you get a prcture of the sun, made entirely in the red light of hydrogen, made up of a vast number of tiny slices. Suppose that you want to examine the sun in the light of the red glow of hydrogen. The first slit is set in the middle of the sun, and you look, through an eyepiece, at the dark red line of hydrogen in the spectrum. Now suppose that you have a sec-- ond slit, just the width of this Jine, and you adjust it so that all cf the spectrum, except the line itself, is cut of. Then you will see that the line is not dark, but has a faint red light of its own. Now move the slit under the solar image. This will move the red line, so you move the second slit, and make it follow the line. To save trouble, you attach a motor, and the proper gearing to the two slits, so that they both move across the sun at exactly the right speed. eeul UE NA ETAE ELEA PE CT ETE Eo e enA cE Ee o Ee oi t o ie c ty One moving slit is not sufficient, for when it moves, the spec-- trum, on the other side of the prisms or grating, also moves, and all that the observer sees is a spectrum, with its various lines, passing across the fhield of view. In order to get a good spectrum, the light must first be passed through the narrow slit. The image of the sun, as formed by a large telescope. may be several inches in diameter, and so the slit cannot take in more than a very small slice of the sun at a time. _ But if the slit is as long as the diameter of the solar image, and is moved in the direction at right angles to its length, then the entire sun may be covered. cf high power, the light from the inner part of the sun is spread cut into « very faint spectrum, but the light of the prominence itself goes through undisturbed. The glare of the background is no longer so great that it drowns out the fainter glow of the prominence. T TNHIS sort of spectroscope shows oniy a tiny bit of the sun F at a time. In order to reveal the entire sun in the light from a single element in the chromosphere, Dr. Hale invented, in 1895, a spectroheliograph. Elames A Epepiece throug which image of " solar spectrum is observed. ie IN Tob 3 Aid) is / a %An )00 l First murrotr «L J L JV L t ) ) )