The Birmingham age-herald., 1922-07-02


 We have frequently referred to the fact that the name of the star Antares, means the rival of Mars" " This star Is at A, Figure 1. As Mas is now close to Antares. it Is good time to compare these bodies, To the naked eyes they look very sim | lar. Mars is now the brighter of the two. but this Is not always true The brightness of Antares does not change. It is of 1.2 magnitude. The magnitude of Mars changes greatly chiefly because of It's varying dis tances from us, The magnitude changes from minus 2.7 when nearest to plus 20 when farthest, a change of 47 maKnitudes. This means that 1ts greatest brightness is 76 times its least At present July 1, its magni- tude is minus 20. 1t is now 10.7 times as bright as Antares to us. Both bodies have a reddish color. It Is probably this fact which suggested the name for Antares.
 h most respects the bodies differ greatly. One may notice differ enee ia their appearance. Antaros wrinkles. Mars does not, or at least much loss than Antares. The light coming to us from these bodies must pass through the earth's atmosphere. This atmosphere is undergoing change all of the time. The light thus comes to us under everchanging conditions of the air and these changes cause irregularities in the refraction, causing the light to ap- pear to be coming from a moving point. That Is. the point seems to move about. In the case of stars the light comes practically from a single .pelnt. as the stars are so far away that even though they are of immense size we cannot distinguish them from roints. We are usually unable to say more about the size of the stars than that they are too small to he measured. The method developed by Professor Nicholson for measuring the diameter of stars has made 1t possible to determine the dlameters of a few Antares was ouc of these. It's diameter was found to be four -hundredths of a second, a diameter so small that We are very accurate when we say that this star is merely point of light No star appears to be more than a point of light in any telescope. The telescope incr eases the brightness. but does not have power enough to enable us to see the star as more than point.
 With Mars the case is different In n telescope we sec not point, but a sharply defined disc whose diameter is now 20 seconds. Each point of thls disc Is dancing about as the star, Lut as some points move ono way and other points in different direc- tons, the position of the whole disc is practically unchanged and hence the planet does not twinkle like the stars.
 Mars and Antares are essentially different. Mars is planet revolv- ing about the sun and shining be- cause it reflects the sunlight which falls upon it. The planet itself Is no more luminous than the earth. An tares is a body which, like the sun, shines because 1t Is self-luminous IL may have planets like the earth and Mars revolving about tive cannot tell.
 Distances nnd Sizes
 As both the earth and Mars are moving about the sun the diftance between them Is an eyer-changing quantity varying from about 35 to 247 million miles. Az present its dis tance is 43.00O.000 miles. The dis tances of Antares is somewhat un- certain because so great. It Is thought to belong to moving cius- ter of stars in Scorpio and Centau- rus. If it does then it's distance can be considered well known. Determi- nation of the distance by other less accurate methods gives somewhat different result. We accept Russeil's