THE HEAVENS IN JUNE 



•our own, revolving about them, we at 

 present have no means of knowing'. 

 The Planet Mercury. 



This most interesting" little work! 

 will be in so unusually favorable a po- 

 sition for observation during the pres- 

 ent month that the reader should not 

 fail to obtain a view of it. On the 

 evening of June 18, he will find it 

 shining in the twilight glow, far to 

 the northwest for an hour and a half 

 after sunset, but it also may readily be 

 detected on several successive even- 

 ings both before and after this date. 

 The path which this planet pursues 

 about the sun lies far within the orbit 

 of Venus, Mercury, in fact, being but 

 little more than one-third as far from 

 the sun as the earth is, and conse- 

 quently the planet is almost always 

 hidden in the sun's rays It can only 

 be seen with the eye just after sunset 

 or just before sunrise a short distance 

 from that part of the horizon below 

 which the sun is shining. 



When, however, the observer sees 

 the planet for the first time he will 

 probably be surprised by its brilliancy ; 

 toward the middle of this month it 

 will shine with nearly twice the 

 brightness of a first magnitude star, 

 a brilliancy due to the intense sunlight 

 which falls upon it, for upon any part 

 of this little world seven times as 

 much light and heat are being poured 

 down as upon a similar part of our 

 earth. 



The year on Mercury is only eighty- 

 eight days long, so that on this planet 

 each of the four seasons would be less 

 than a month in duration. But beside 

 this, its path about the sun is so far 

 from being perfectly circular that 

 when the planet is nearest the sun it 

 receives more than twice as much light 

 and heat as when farthest away. To 

 an observer on the planet the sun 

 would appear more than twice as large 

 as we see it, and if we add that one- 

 half of this world is always turned to- 

 ward the sun and one-half is turned 

 away from it, so that on one-half of 

 the planet there is perpetual day and 

 on the other half unending night, it 

 becomes evident that conditions on 

 this little world must be very different 

 from those on our own. 



The Planets in June. 



Venus continues to shine brilliantly 

 in the west throughout the month. On 

 June i it is near the center of the con- 



stellation Gemini, but by June 30 it will 

 have moved out of this constellation, 

 entirely across Cancer, and into the 

 western border of Leo. Having passed 

 Saturn on May 16, it is now drawing 

 continually nearer to Mars, but it will 

 not finally overtake this planet until 

 August 5. Venus in the telescope now 

 appears about as the moon when three 

 days past the full ; it will not become 

 one-half full and enter the crescent 

 phase until September 18, and from 

 now until more than a month after 

 this date it will continually grow 

 brighter. 



Mars is also moving rapidly east- 

 ward but its motion is somewhat 

 slower than that of Venus and hence 

 it is being steadily overtaken. During 

 the month it moves from the eastern 



//.2! 





Figure 3. The Star Cluster in Hercules (at B, 

 Figure 1), as drawn by Sir John Herchel. 



borders of Cancer to a position a little 

 left of and below the bright star Regu- 

 lus. The announcement recently made 

 that traces of water vapor have been 

 found in the atmosphere of Mars, will, 

 if confirmed, possess the highest in- 

 terest and importance. For the known 

 presence of this water vapor would 

 render it practically certain that the 

 polar caps of the planet are true snow 

 caps and would indicate that this 

 world is as warm or warmer than our 

 own. If the result is made certain, we 

 will therefore know that Mars is far 

 more suited to the existence of such 

 forms of life as exist on our own earth, 

 than we have hitherto had evidence of 

 its being. 



