A Field Book of the Stars Part 13

This completes the list of wonders visible at this precise time, but the stars apparently are never still, and doubtless, while the student has been pa.s.sing from one constellation to another in the western and southern skies, others have been rising in the east and northeast.

At ten P.M. the Lyre is well up, and Ophiuchus and Libra can be discerned. At midnight Scorpius and Cygnus are ready to claim the attention. By two o'clock A.M., Aquila, Delphinus, and Sagittarius have risen, and at break of day Andromeda, Pegasus, and Capricornus can be seen if the student has had the courage to remain awake this length of time.

In no way can the seeming movement of the stars be better understood than by actual observation. The observer must bear in mind that the movement is an apparent one: that it is the earth that is moving and not the stars. He has only to think of the a.n.a.logy of the moving train beside the one that is standing still, and the true state of affairs will at once be evident.

To further appreciate this apparent change in the situation of the constellations, the student should refer to the large plates successively. In each successive one he will note the advancement westward of the constellations mentioned above, rising in the east late at night.

The student can best get an idea of this westward apparent movement of the stars by noting the position of some bright first-magnitude star from night to night. He will soon be able to calculate the position of this star a month or more ahead, and this calculation applies to all the constellations and stars.

It is not within the scope of this work to go into this matter in detail. The author merely desires to mention this fact of apparent change of position in the stars, a fact that will be noticeable to the observer in a short time, and a fact that it is hoped he will be able to explain to his own satisfaction with the aid of the foregoing remarks.

It will be noticed that the stars on the diagrams are all numbered and lettered. The numbers refer to the magnitude of the star,--that is, the brightness of it, the first-magnitude stars being the brightest, the second-magnitude stars two-and-a-half times less bright, etc.

The letters are those of the Greek alphabet, and the student if not familiar with it is advised to consult a Greek grammar.

In the text, in referring to certain stars in the constellations, the genitive case of the Latin name of the constellation is given; for example, Vega is known as a Lyrae, meaning alpha of Lyra, Aldebaran as a Tauri, alpha of Taurus, etc.

The twilight hour affords an excellent opportunity of fixing the relative positions of the first-magnitude stars in the mind, for at that time they alone, save the planets, are visible.

METEORS, OR SHOOTING-STARS.

As this work is designed primarily to cover what is observable in the starlit heavens with the naked eye, the subject of meteors, or shooting-stars, comes properly within its scope.

There are few persons, if any, who have not witnessed the sight of a splendid meteor speeding across the sky, and such a sight always calls forth exclamations of wonder and delight.

Apparently these evanescent wanderers in s.p.a.ce are without distinctive features, and baffle cla.s.sification; but, like all that nature reveals to us, they have been found, for the most part, to conform to certain laws, and to bear certain marks of resemblance that permit of their identification and cla.s.sification.

By careful observation for over fifty years the meteors, generally speaking, have been so arranged that they come under the head of one of the nearly three hundred distinct showers which are now recognized by astronomers.

Many of these showers are too feeble and faint to be worthy of the attention of one not especially interested in the subject, but certain ones are well worth observing. There is always a pleasure in being able to recognize at a glance a certain definite manifestation of nature, be it a rare flower or a flas.h.i.+ng meteor.

The generally accepted theory respecting the meteors is that they were all originally parts of comets now disintegrated, and the four well-known showers of April 20th, August 10th and 14th, and November 27th, bear testimony to this theory.

The apparent velocity of the meteors is between ten and forty-five miles a second, and their average height is about seventy-six miles at first appearance, and fifty-one miles at disappearance. Occasionally a meteor is so large and compact as to escape total destruction, and falls to the earth. Specimens of these meteorites are to be found in our best museums.

I have seen fit to divide the princ.i.p.al meteor showers into four groups, according to the seasons in which they appear, and have placed them respectively at the conclusion of each season's work on the constellations.

By radiant point is meant the point from which the meteors start on their flight. This point is an apparent one, however, due to an illusion of perspective, for the meteors really approach the earth in parallel paths.

The dates given for these showers are those of the maxima, and the meteors should be looked for several nights before and after the dates specified.

The showers that are to be seen after midnight are, unless of special note, omitted.

There are, besides the meteors that have been cla.s.sified, certain shooting-stars that apparently have no determined radiant point. These are called sporadic meteors.

In these lists of meteors, the radiant point is only approximately given; for scientific purposes a far more exact position is required in terms of right ascension and declination. There are several good lists of meteoric showers to be obtained, which afford this information for those who care to pursue the matter more in detail.

See the Rev. T.W. Webb's book, ent.i.tled _Celestial Objects for Common Telescopes_. For purposes of identification, the radiant points here given will be found for the most part sufficient.

NOTE.

Many readers of this book may be the fortunate possessors of small telescopes. It may be that they have observed the heavens from time to time in a desultory way and have no notion that valuable and practical scientific research work can be accomplished with a small gla.s.s. If those who are willing to aid in the great work of astrophysical research will communicate with the author he will be pleased to outline for them a most practical and fascinating line of observational work that will enable them to share in the advance of our knowledge respecting the stars. It is work that involves no mathematics, and its details are easily mastered.

THE NAMES OF THE STARS AND THEIR MEANINGS.

ACUBENS, a _Cancri_, "the claws."

Situated in one of the Crab's claws. It is white in color and culminates[1] March 18th.

A-DAR-A, e _Canis Majoris_, "the virgins," a name for four stars, of which Adara is brightest.

Situated in the Dog's right thigh. It is pale orange in color, and culminates Feb. 11th.

ADHIL, e _Andromed_, "the train of a garment."

Situated in the left shoulder of the chained lady.

ALADFAR (al-ad-fr), _Lyr_, "the talons" (of the falling eagle)

AL BALI, e _Aquarii_, "the good fortune of the swallower."

AL-BI-REO, or AL-BIR-O _Cygni_, origin doubtful. Means the beak of the hen.

Situated in the beak of the Swan and the base of the Cross.

Its color is topaz yellow, and it culminates Aug. 28th.

ALCAID, ? _Urs Majoris_. _See_ Benetnasch.

ALCHIBA (al-ke-b), a _Corvi_, "the tent," the desert t.i.tle for the constellation.

Situated in the eye of the Crow. Orange in color.

ALCOR (al-kr), g _Urs Majoris_, "the cavalier" or "the rider."

Situated close to Mizar in the handle of the "Dipper."

Silver white in color. The Arabs called this star "Saidak,"

meaning "the proof," because they used it to test a good eye.

AL-CY-O-NE, ? _Tauri_.

Greenish yellow in color. The brightest of the Pleiades.