Part 3 (1/2)

Sk.--streak-leaving meteors.

T.--train-leaving meteors.

THE CONSTELLATIONS OF SUMMER.

[Ill.u.s.tration: Maps showing the princ.i.p.al stars visible from Lat. 40 N. at 9 o'clock, July first.]

DRACO (dra-ko)--THE DRAGON. (Face North.)

LOCATION.--About 10 from a Urs Majoris--from a to d is 10--slightly south of, that is above, the line from a to Polaris, is Giansar, ? in the tip of the Dragon's tail. Above ?, and almost in line with it, are two more stars in Draco, which form with two stars in Ursa Major a quadrilateral. (See diagram.) Draco now curves sharply eastward, coiling about the Little Bear as shown, then turns abruptly southerly, ending in a characteristic and clearly defined group of four stars, forming an irregular square, representing the Dragon's head. This group is almost overhead in the early evening in summer. The star in the heel of Hercules lies just south of the Dragon's head. The brilliant Vega will be seen about overhead, 12 southwest of the Dragon's head. Eltanin, one of the Dragon's eyes, is noted for its connection with the discovery of the law of aberration of light. It is of an orange hue, while the star , near it, is white. Note Thuban, once the Pole Star, at one corner of a quadrilateral that Draco forms with Ursa Major.

Thuban could be seen by day or night from the bottom of the central pa.s.sage of several of the Pyramids in Egypt.

The rising of Eltanin was visible about thirty-five hundred years B.C.

through the central pa.s.sages of the temples of Hathor at Denderah. The Egyptians called Draco ”The Hippopotamus.”

Vega and the four stars in the Dragon's head offer an opportunity to compare the first five stellar magnitudes with which all should be familiar.

[Ill.u.s.tration: DRACO]

LYRA (li-ra)--THE LYRE.

LOCATION.--Lyra may be easily distinguished because of the brilliant Vega, its brightest star, which is situated about 12 southwest of the Dragon's head. It is unmistakable, as it is the brightest star in this region of the heavens, and the third brightest in this lat.i.tude. In July and August Vega is close to the zenith in the early evening.

The six bright stars in Lyra form an equilateral triangle on one corner of a rhomboid. A very characteristic figure.

e is a pretty double for an opera-gla.s.s, and a 3” gla.s.s reveals the duplicity of each star of this pair. e is therefore a double double.

? is a double for a good gla.s.s.

is a variable, changing from magnitude 3.4 to 4.4 in twelve days. At its brightest it is about equal to its near neighbor ? Lyr.

The noted ring nebula lies between and ?. A 3” gla.s.s reveals it but a powerful telescope is required to render its details visible.

If the distance from the earth to the sun equalled one inch, the distance from the earth to Vega would be 158 miles.

Vega was the first star to be photographed, in 1850. It is visible at some hour every clear night, and has been called the arc-light of the sky. Its light has the bluish-white hue that suggests ”a diamond in the sky.”

The spectroscope reveals that Vega is a star probably only in its infancy, as hydrogen is its predominating element.

[Ill.u.s.tration: LYRA]