400 



THE GUIDE TO NATURE 



as the star at C, and during the next 

 few days it grew even brighter, after 

 which it giew rapidly fainter, and 

 in the course of a week was lost to 

 the naked eye, though it was still easily 

 seen in a small telescope. It has since 

 been steadily fading away, and will 

 soon doubtless be only visible with 

 lenses of the largest size. 



What the cause of these remarkable 

 objects is, is still wholly unknown. 

 They always appear suddenly, rising 

 from invisibility to great brilliance 

 within a few clays, or even within a 

 few hours. They may remain shining 

 conspicuously in the sky for a few 

 days, weeks, or even months, but soon 

 they begin to grow rapidly fainter until 

 finally they appear to sink into very 

 faint, greenish nebulas. 



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Figure 3. Telescopic appearance of the planet Jupiter. 



An examination of photographs of 

 this region of the sky made on March 

 io and 1 1 showed that on the first date 

 no star was in the exact position of the 

 nova so bright as the 11.5 magnitude; 

 on the second date the nova had ap- 

 peared, and was of the fifth magnitude. 

 On still earlier plates, however, the 

 place of the new star was taken by a 

 star of the fourteenth magnitude. If 

 this faint object is the nova itself, its 

 brightness must have increased 15,000 

 fold in the course of a few days. 



It is possible that a sudden blazing 

 out of a star in the heavens is caused 

 by the meeting of an old and dark 

 star with a meteoric cloud. The col- 

 lision and friction of the meteors of 

 the cloud may heat the cold star to in- 



candescence, or may merely weaken its 

 crust and enable the imprisoned gasses 

 to rush out. Some astronomers think 

 it more probable that the outburst is 

 caused bv the near approach of two 

 dark suns, the enormous gravitational 

 pull which results tearing apart the 

 crust of one of the stars and thus en- 

 abling the hot, inner material to escape 

 as before. Still others believe that the 

 wonderful brilliance is due to an ex- 

 plosive outburst in the body of a 

 slowly-shrinking star, and that no out- 

 side influence need be imagined to ac- 

 count for it. What the cause of so 

 enormous an explosion can be we do 

 not know, and, indeed, the whole mat- 

 ter is one of the many problems in 

 astronomy still awaiting solution. 



THE PLANETS IN MAY. 



Mercury is a morning star, reaching 

 its greatest distance west of the sun 

 on the afternoon of May 13. For a 

 few days before and after this date 

 it may be found shining brightly in the 

 dawn, almost due east, rising about I 

 hour 30 minutes before sunrise. 



Venus is also a morning star, but is 

 too near the sun to be well observed. 

 On May 1 it rises 1 hour 5 minutes be- 

 fore sunrise, which time is lessened to 

 40 minutes by the end of the month. 

 It will not finally pass the sun and be- 

 come an evening star until July 5. 



Mars moves very rapidly eastward 

 during the month from Gemini to Can- 

 cer. It passes 2 degrees above the 

 bright star K, Figure 1, on May 5, 

 and just below the Praesepe and be- 

 tween the stars L and M on June 8. In 

 one day it moves over the sky an 

 amount equal to the apparent distance 

 across the moon. It is now very far 

 away from us and appears in the tele- 

 scope as only slightly more than one- 

 half full. 



Jupiter is now just entering the even- 

 ing sky. It rises a few minutes after 

 9 o'clock on May r, and at 7 o'clock on 

 May 31. It is in the southeast, in ex- 

 cellent position for observation. 



Saturn passes the sun and enters the 

 morning sky at noon on May 14. On 

 May 27, at 4 P. M., it passes Venus, 

 but both bodies are then too near tke 

 sun to be well observed. 



