REALM OF THE GALAXIES

[Music] [Music] From the earliest times, men have looked into the heavens and wondered about the immense, mysterious universe into which we are born. Astronomy is a wonderful example of man's ingenuity and skill. The heavens cannot be studied at first hand, but the information rides in on beams of light or radio waves from outer space. Using modern telescopes and other techniques, astronomers have explored vast regions of the universe. Our story today, the realm of the galaxies, is about these explorations and about what has been revealed and is yet to be revealed by light from the heavens to reach us at 186,000 m per second. Farther out in the Milky Way, there are billions of stars ranging from the brightest super giant stars to stars of medium brightness like our own sun to small dim dwarfs. There are also stars that change in brightness, some of them pulsating regularly. There are also patches of gas and dust called nebula. These gas and dust clouds and these billions of stars make up a single system, the galactic system or Milky Way. For a long time, it was thought that this system comprised the entire universe. Certain mysterious luminous patches, however, could not be resolved as either stars or clouds of gas and dust. And for many years, astronomers puzzled over them. Astronomers do not usually live on mountain tops. They live near research centers where most of their time is spent studying results of their work on the mountain. Dr. Alan R. Sandage is one of the astronomers on the staff of the Mount Wilson and Palomar Observatories. Ever since moderately sized telescopes have been pointed toward the sky, astronomers have seen in addition to the stars and the planets of faint patches of light between the stars and these patches have been called nebula. The nature of these objects uh remained obscure until the late 1920s. There were two schools of thought on the subject. One school uh maintained that the nebula were um objects in our own stellar system nearby and of small size. The other school believed that some of these objects were of enormous size and at great distances from us. In the 1920s, the late Dr. Edwin Hubble turned the newly completed 100-in telescope at Mount Wilson toward one of the brightest of these hazy patches in the constellation of Andromeda. Photographs taken with the 100-in telescope revealed greater detail in the center. In the arms, pinpoints of light could be resolved as individual stars. Several series of photographs revealed types of familiar stars which had been observed and studied in the Milky Way. The stars that band of light was a great distance away. A huge separate system of stars called the great galaxy in Andromeda. For the most part, the universe was empty. But here and there, separated by vast intervals, were other great stellar systems. each composed of billions of stars, islands in a sea of space, the major structures of the universe, nature's largest building blocks called galaxies. Within range of the large telescopes, there are over a 100 million more. Nearly all the galaxies fall into very few main groups of ellipses and spirals. The ellipses ranged from this disc-like satellite galaxy of the great galaxy in Andromeda to this shape, a nearly perfect sphere. The spiral galaxies which rotate about a massive center have closed arms such as this one in the constellation of Virgo or partially opened arms as this galaxy in Ursa Major or open arms from the ends of a bar as this galaxy in Arerodonis or normal open arms as this almost perfect pinwheel of light in the region of Pisces. The galaxies seemed to be related members of a single family constructed on a fundamental pattern which varied through a limited range. Our own galaxy could be fitted into the pattern. This might be the Milky Way. All the stars seen here would be a thousand times brighter than our sun, which would be a small invisible star on the outer rim of this galaxy. Astronomers had opened up a universe a thousand million times larger than had been wildly imagined before. But the galaxy still stretched out beyond the reach of the 100-in telescope. The new 200-in telescope plus more sensitive photographic plates and photoelectric cells has greatly enlarged our view of the universe. This universe is composed of units of matter called galaxies. And astronomers hope by studying the galaxies in the observable region to infer the nature of the entire universe. A part of this program is to redetermine the distance scale by a search for new sephiid variable stars. This is a galaxy called M33 in the constellation of triangulum. It is one of the galaxies in our local group. We see it here in a negative print. In this 200in view, we begin to see fainter images of stars in this galaxy. Some of these stars might be giant sephiid variables. It takes as many as 50 to 100 new photographic plates of a particular region of M33 to discover and to measure the light variations of new sephiate variable stars. This region will be photographed and measured during the next few nights at the 200-in telescope on Paly Mountain. The observatory car leaves the research center in Pasadena at 8:00 in the morning. The drive south, which takes about 2 and 1/2 hours, takes us far away from the lights of the big city. Lights which would ruin the sensitive photographic plates. The dome of the observatory can be seen from a great distance. If the visibility is good and the sky is clear, I can count on going ahead with my original plans for direct photography and photoelectric measurements. But if clouds threaten the visibility, the program might have to be changed to direct photography only. If the weather and visibility are very bad, we are out of luck. Telescopes are built above the lower layers of the Earth's atmosphere. This one is 5600 ft above sea level. In a place called the monastery, food, beds, books, and the company of other astronomers are available for the few free moments on the mountain. In the cold night air, an electric flying suit is a great comfort. [Music] When the huge shutters open, the twilight sky reveals the largest and most delicate optical and photographic instrument in the world. A night assistant is on duty. From his control panel, the night assistant controls the movement of the millionpound instrument. It rotates east to west on a large horseshoe bearing supported on a film of oil only 3,000 of an inch thick. There is so little friction that a 1/12th horsepower motor can drive it easily. This motor and a clock mechanism compensate for the Earth's rotation by constantly and automatically moving the telescope west as the Earth spins eastward during the night. On another set of watchmakers bearings, the instrument moves in a south to north direction. The telescope consists primarily of a long metal tube with a concaved mirror bolted to its base and a cage for an observer at the top where the image reflected by this mirror comes into focus. An elevator on a curved track takes the astronomer to the observer's cage. As the diaphragm opens, the giant mirror 200 in in diameter, equal to a million human eyes, reflects the still light sky above. When preliminary preparations are complete, the coordinates of the area to be photographed are given to the night assistant. Right ascension 1 hour 30 minutes 38 seconds. Declination plus 30° 20 minutes 14 seconds. What the astronomer himself sees is limited. A great telescope is used as a photographic or a photoelectric measuring instrument. He sees enough to make final adjustments with a second set of controls. The photographic plate, which is exposed, sometimes for hours, is inserted. With his secondary controls, the astronomer keeps a guide star centered in the crosshairs of a viewer. The Earth's atmosphere, with its changing temperature and pressure, plays tricks on the narrow beams of light. Most of a night like this is spent checking the crosshairs, guiding the telescope, changing the plates in complete darkness while listening to music, or thinking about this strange laboratory 55 ft above a huge mirror, gathering light that left a distant galaxy many ages ago. [Music] The largest and most valuable piece of glass in the world began as a flat thick Pyrex disc which was made into a perfect parabolic mirror. After more than 11 years of careful grinding, polishing, and testing, using a small light source and checking the reflections, it was finally corrected to 2 millionth of an inch, so that light from distant objects entering the telescope is accurately reflected and forms a nearly perfect image at a point of prime focus where photographs can be made or intensity of light measured. Showing through the thin face of the mirror is the ribbed honeycomb structure of the back which gives the glass rigidity and strength. The center hole allows light waves to be reflected back through the mirror itself for greater magnification of the image. The back has 36 supports, each with counterbalances, so that a proportionate amount of weight is carried by each support for any position of the mirror. On the first morning at the mountain, after a period of 24 hours without sleep, at a time when the rest of the world comes to work, an astronomer goes to sleep. The results of four nights work on the mountain takes many weeks to study and to measure. A research associate sometimes assists. The new photographic plates taken at the mountain are compared to earlier plates in a blink comparison machine. As two light sources are alternated from the early plate to the recent plate, stars that have changed in brightness appear to change in size. They appear to wink at you through the blink machine as the lights are alternated. The position of these variable stars are noted. Some of these variable stars are the rare giant sephiid variable stars. On a photographic photometer, apparent brightnesses are measured and compared with brightnesses measured directly at the telescope. For measurements made of the plates, an iris is placed around the star. With these measurements and a graph of sephiid variables of known absolute brightness in our own galaxy, we can find the distances of the new sephiid variables in M33. And finally, the distance of the galaxy itself. At the moment, the distance to the galaxy M33 is estimated to be 2 million light years. This distance is a factor of three uh greater than Hubble had estimated in 1936. The more remote, extremely distant galaxies, the true inhabitants of outer space, are now believed to be some five to eight times more distant than Hubble had believed. The change in Hubble's distance scale is one of numerical detail only, not of fundamental philosophy or direction of attack. There are two Okay. [Music] [Music]