The Birmingham age-herald., 1921-01-02
The Starry Skies m January
By PROFESSOR BARTON, fl the University of PennsyIvanfa


 The great difference which exists in the brightness of the stars in different parts of the sky is well illustrated in the January sky. In the portion of the sky represented on our map there are o2 stars which are brighter than the sec ond magnitude. Suppose we divide this map into two equal parts by drawing a line from north to south. This line is called the meridian. We shall then find tEat 20 of these bright stars lie in the eastern half and only two, the eighth and sixteenth in order of brightness, lie in the western half. One of these is Deneb in Cygnus and the other is Alpha Persei, which is just west of the dividing line. It is common notion that the stars are brighter in winter than in sum n.er because of the temperature or at m ospheric conditions. This is not the reason. There are actually present stars whose intrinsic brightness is greater than that of the summer sky.
 THE PLANETS
 None of the brighter planets are in good positions. Venus can be seen low in the west just after sunset At the first of the month its position is outside the limits of our map. Its position at the end of the month is shown on the map. Jupiter and Saturn lie in Leo just beyond the eastern limit of the maII. They rise soon after o'clock. Mars passes Uranus January g. A few hours later the same day Venus passes Cranus. A few hour later still Venus passes Mars. At this time these three planets will De closely grouped but low in the sky. Mars is now near the sun IL will be passed by the sun on June ze. It will not be in good position at any time during the year. Jupiter and saturn will be visible in the early evening from February until August
 In Figure ? we show the motions or the earth and Venus. Lines are drawn joining the position of the earth on each of eight dates with the corresponding po- sition of Venus and with the sun. The angle whose vertex is at the earth De- tween the lines joining the earth with the sun and with Venus is called the elongation of Venus. This angle reaches it's greatest value on February 9, the angle then being little under Al de- grees. Venus is then at it's greatest east ern elongatiol. After this time the elon- gation decreases until it becomes zero cn April 23, at which time Venus passes from the eastern to the western side or the sun. It changes from an evening to a morning star Venus is then at in- ferior conjunction. Venus is then closest to the earth at a distance of about 2C. 100000 miles Venus reaches it's great est western elongation on July l. It IS then visible in the morning before sun rise The distance of Venus from the earth changes. 1t is not brightest when closest, for Venus shines only by ref'ec- ing the sunlight which falls upon it, and when closest the illuminated side is turned away from the earth. Venus IS brightest March 1T in the evening ana May in the morning.
 Since the angle of elongation is in creasing, it is evident. that Venus will be farther east of the sun each night and set later until Februarye9, and then earlier each evening until it sets with the sun of April 22. Starting with Feb ruary g, the line joining the earth with Venus will be seen to be moving farther from a horizontal direction until March s1 the planet is said to be stationary. It then ceases it's eastward motion among the stars and begins it's west ward motion. This is illustrated in Figure 3. in which we draw lines from the earth in the direction and of the length shown in Figure 2 for each posi- tion of the earth On May II the west ward motion ceases and the eastward motion begins again.
 WHAT IS A YEAR?
 At the beginning of new year 1t may be well to ask what a year is? Nearly, if not everyone, thinks he knows what year is, yet their defini- tions would probably differ widely, There are several kinds of years. We ordinarily think of year as the inter val designated on the calendar as a year-namely, the civil year. Civil years are either common years of S65 days or leap years of 366 days. It be- gins at midnight of December 31 and ends at midnight of the following De- cember 91 The year did not always begin at this time. Using each fourth wear as a leap year. the ayerage length