Norwich bulletin., 1920-12-04

One of the most interesting problems Of astronomy is that concerning the nature of the spiral nebuiae. writes c. H. Currier in the Boston Transcript In brief, the question to be settled is this: Are the spiral nebulae merely distant star clusters or are they masses of glowing gas? Sir
 William Herschel was one of the first to
 argue for the stellar cluster or island universe theory He had noticed that star clusters. which appeared to be nebu- lous masses of gas in small telescopes,
 could, by the use of larger instruments
 and higher magnifying powers, be re-
 solved into their component stars. He
 argued that all nebluae could in the same
 way be resolved into star clusters by the use of a sufficiently powerful telescope. This island universe theory was accept
 ed as the correct one for many years. Then came the spectroscope. and about 1860 Sir William Huggins showed by the use of this wonderful instrument that some of the nebulae at least are clouds of gas, since they give a discontinuous spectrum containing only a few bright lines. The spectrcsco did not, however. settle the question as far as the spiral
 nebulae are concerned. for these nebulae give q continuous spectrum like that l which we get from the stars. Such a l spectrum might, however, be obtained 1 from a glowing mass of gas under high pressure
 1 Within the past few years careful study of the spiral nebulae has shown l some interesting facts about them. They
 are extremely numerous. probably 700,000 being within the range of our best tele- scopes. They are never found within the
 Milky Way itself, but occur in greatest numbers where the stars are fewest. They are moving through space at very high i velocity. averaging nearly 500 miles per second. more than 25 times the average stellar velocity. Some of them have been shown to be rotating. Comparison of ob- servations made n any years apart has l failed to show evidence of change in DO. sition. in spite of the very rapid motion indicating that the nebulae must be ex trenaely remote.
 These and other facts have led to re turn to the older island universe" theory We have come to look upon these spira i nebulae as star clusters outside of ou own stellar system. On account of tn.
 l spiral formation of these clusters it il
 probable that our own cluster is also Q Il spiral structure. In other words. tn Milky Way may be of spiral form ant
 represent our solar sub-universe.
 |, Additional evidence in favor of the sta
 cluster theory has been furnished within , the past two years by the discovery of l or 15 newt stars in spiral nebulae. Nov
 & new" star or nova is not a new crea
 tion but simply one that suddenly in creases in brightness on account, proba
 bly,, of collision or internal eyplos,or P Naturally novae anrears most frequentl where the stars are most numerous, as ! our Milky Way, and the fact that so man
 have been found in spiral nebulae wcul e seem to indicate that the latter are reall
 star clusters ei The sun begins the months over 21 dc v grees south of the equator and reaches ii 1 position farthest south on the 21st g VI 1017 D. m., at which time winter begin
 At this time, in our latitude, the day
 the shortest of the year. being over si hours shorter than the longest day = June. After the 21st the sun will moN northward again and the days will beg s to lengthen. Just at midnight on the Fl Il as the old year is ending and the new or ' beginning, the earth will be in perihelio 0 the position in it's orbit nearest the sun. The moon will be in last quarter on Il :, 2d at 11.29 a. m., new on the 10th at 5.t
 a. m. in first quarter on the 18th at g.. Il g. m, full on the 18th at 73S| .. m, al ? in last quarter again on the 21st at IL. :, D. m. It will be in apogee or the 18th al ,s in perigee or the 25th. It will run lo IT on the 10th and high on the 24th, eros n ing the equator on the Sd, 18th and 3ot s In it's journey around the zodiac it W . pass the planets in the following orde e Jupiter and Saturn on the 3d. Mercury ,5 the Sth. Venus on the 14th. Mars on t ;s 18th, Uranus on the 18th. Neptune on [ " 18th, and Jupiter and Saturn again on |
 30th.
 S. Mercury will be in greatest weste l. elongation on the Sd and hence will is visible in the morning sky for few da ID before and after that date. It will of found low in the southeast before sunri f. in the constellation Libra and will be | le brightest object in that part of the sl lg Venus is the most conspicuous object st the southwest ill the early evening setti lg at e.4S D. m. the 1st or 7.50 on the 31 le It will move during the month northwa IS and eastward from Sagittsrius into Cap le cornus. It is getting brighter as it . ts breaches nearer the earth, while at | us same time the illuminated surface nd creases during the month from IS to te per cent.
 e. Mars is still visible low in the southw
 at sunset. setting about S.15 throuhgt of the month. IL will move northward a lis eastward from Capricornus into Aquari as Jupiter is fast coming into favora or position for observation, rising at 115 'n' m. or the 1st or 10.14 on the 31st. It