A Check List for the Sound Beach Observatory 



The Sun, Our Star, Radiates Light and 

 Heat in Every Direction. 



The Diameter of the sun is 866,400 

 miles; that is, 109.4 times that of the 

 earth. 



The Surface is 12,000 times that of the 

 earth. 



The Mass is 333,000 times that of the 

 earth- 



The Density is about Y\ that of the 

 earth or 1.4 times that of water- 



The Rotation from the east to the west 

 averages 25-35 days. The rotation is 

 faster at the equator than on either side, 

 showing that it is not a solid mass. 



The Diameters of the Spots range from 

 about 500 to 60,000 miles- This may be 

 estimated by comparing the spot with the 

 diameter of the sun. 



The Planets, Our Family, All Recei 

 from the Sun. 



miles- The thickness of the rings about 

 100 miles. Composed of "a swarm of 

 separate particles, each an independent 

 moon." Four other moons, not visible 

 except in largest telescopes, are Themis, 

 Phoebe, Hyperion and Mimas. 



Uranus's Moons : Seen only in largest 

 telescopes- Ariel, Umbriel, Titania and 

 Oberon. 



Neptune's Moon : Seen only in moder- 

 ately large telescopes- One, not named. 



Densities of the Planets. The only 

 planet which is lighter than water is 

 Saturn, though Jupiter, Uranus, and 

 Neptune are each but little heavier than 

 water. The four inner (earth-like) plan- 

 ets are of course much heavier. The 

 larger ones have not yet had time to cool 

 off : it is their high temperature that 

 keeps them so expanded. 



ve Light and Heat in Varying Degrees 



Jupiter's Older Moons — Four in order 

 from Jupiter: I, Io ; II, Europa ; III, 

 Ganymede ; IV, Callisto. (Five others are 

 known but they are not seen except in 

 largest telescopes). 



Saturn's Moons : Iapetus, Titan, Rhea, 

 Dione, Tethys, Enceladus. This is in 

 order from most remote. Rings : A, ex- 

 terior diam. 173,000 miles, 12,000 miles 

 wide. The division between it and B is 

 1,800 miles in width. B, 17,000 miles 

 wide. C, "gauze" or "crape," 11,000 



The Stars are Distant Suns. 



Stars visible to naked eye ( estimated ) 



I st magnitude 12 4th magnitude 313 



2nd magnitude 48 5th magnitude 854 



3rd magnitude 152 6th magnitude 2,010 



Total— 3,389 



In whole celestial sphere on moonless 

 nights seen by naked eye only from 6,000 

 to 7,000. An opera glass shows 100,000- 

 In big telescope, 100,000,000- 



There are only twelve stars so bright 

 as to be unquestionably called "first mag- 



