The Waterbury Democrat., 1939-01-27

telescope, be revealed as actually composed of two bodies. We have here 0 star system In which the visible components are about i,800,- GOO miles apart and revolve about each in orbits completed in c period of forty-nine years. The larger component star of the Sirius system Is twice as big and twenty thousand times as bright as the lesser cofn- ponent. However, the lesser member Is particularly noteworthy because 1t Is the first of the ultra dense stars to be discovered. The average den- sity of It's material is about fifty thousand times that of water. Com pare this with the average density Of the earth which Is only i've and one-half times that of water; and the heaviest element known on the earth today, is the rare metal osmlum which Is heavier than lead, mercury, or gold, and has Q density only twenty-two and one-half times that of water. Sirius was also the very first star to be observed to have c motion with respect to the other fixed" stars-a fact discov- cred by Haley in i7i8 and one which has contributed in no small measure to Q better understanding of the sidereal universe which sur- rounds us. About 1920 It's motions were SO well known that the as. tronomer Bessel concluded from cer- tain variations that Q companion must exist and this deduction was proven correct by the discovery in 1862 with . large telescope of the existence of the darker companion.
 Another dog constellation, that Canis Minor, the Lesser Dog, lies directly east of Orion and north- east of Sirius. To the naked eye 1t Is interesting only because of It's brightest star, the first magnitude star Procyon or proeion. The name itself means before the dog' or "forerunner of the dog" as Procyon always rises c little earlier than Sirius. Procyon, like Sirius, is . binary star and the two parts re-. volve about each other once in about thirty-nine years. Taken together their masses are about equal to one and one-third that of the sun and in brightness the sum of their radia. tionS equal about ten suns. Procyons distance from us Is about ten light. years and 1t takes c large telescope to distinguish it's double nature, North of Procyon lies the constel- lation of oemini, or Heavenly Twins, which contains the two bright stars Castor and Pollux. Though officially pollux alone is of the first magni- tude. Castor Is very nearly as bright and the pair seems to merit well the appellation of twins which has been theirs from the earliest times. They are easily recognized as they are only four and one-half degrees apart. Castor Is the one nearer the north celestial pole. Several hun- dred years ago, an astronomer who was making c catalogue of stars called Castor Alpha oeminoruin and Pollux Beta 0eminorum. This may be taken to indicate that at that time Castor was at least as bright as Pollux. As c matter of fact, Castor Is really the more inc teresting star of the two for 1t is easily seen even in small tele- scope to be . double star. Each of this visible pair is itself 6 binary as shown by the spectroscope and a small nearby star, itself Q binary also is 6 member of the Castor sys. tenn. We have in this star, there- fore, really Q system composed of six stars which revolve in pairs about their common centers of grav- ity and as whole about the center of gravity of the entire system. Since Castor is approaching us ct g rate of about eight miles per second and Poliux is retreating at a speed of two miles per second, their proxi- mity and relation Is only an appar- ent one and the Twins do not form a physically united system. This status is, of course, in general true of the great majority of stars which are seen close to another in the sky. Two stars are in the same con- stellation only because they are seen in the same general direction from the earth; they may be separ- ated from one another by truly great distances even in the astron- omic sense. However, there are cases where nearby stars belong to a phy- sically united star group. In parti- cular Is this true of star clusters like the Hyades and the Pleiades in the constellation of Taurus.
 The Planets
 The best opportunity of the year for observing Mercury as an evening star presents itself this month as the planet will be in greatest east ern elongation on the sh. At sun set it will be about 18 degrees above the horizon. Watch for 1t right after sunset and begin your observations about the 10th. They can be extend- ed for a week after the 18th but of course the days nearest the date of greatest eastern elongation are the most favorable. A good opera glass, field glass. or small telescope will be of great help in locatire this elusive planet. The background of the sky will not yet be entirely dark when Mercury disappears from view