Evening star., 1901-07-27
THE SKIES IN AUGUST
Celestial Bodies That Will Be
Above the Horizon.
STARS THAT WE'LL REPAY STUDY
The First Whose Distance From
Us Was Estimated.
PLANETS OF THE MONTH
STARS THAT WE'LL REPAY STUD
PLANETS OF THE MONTH

Written for The Evening Star.
OF the six stars of the first magnitude
which were above the horizon at pm. on
the first of last month, one, Regulus, Is no
longer visible at that hour. The remaining
five may still be seen. but all have moved
thirty degrees, or two hours, farther west
Vega is nearly overhead; Arcturus is de-
clining toward the western horizon; Spica.
between west and southwest, Is too low to
be visible; Antares, in the Scorpion, be-
tween south and southwest is some twen-
ty-five degrees high. and Affair, in the
Eagle, is about twice as high in the south
east. Mars, between Regulus and Spica, is
too low to be visible; the brilliant Jupiter
is just about crossing the meridian, and
six degrees farther east is Saturn.
One Of the finest of the summer constel-
lations is the Swan (Cygnus), better known
to modern stargaZers as the Northern
Cross. Tonight it will be found, at the
hour named, in the east, beneath the star
Vega. 1t may be identified from the cross
like arrangement of its five brighter stars
which, with one exception, are of the third
| magnitude The exception is the star AL
pha-known also as Deneb Cygni-which
marks the head Of the Cross Uail Of the
Swan, and which stands on the photome-
trio scale about midway between the first
and second magnitudes. This star is not
able as one OF the bright stars in which
sensible parallax with the Yale heliometer,
| presumably because OF their enormous re-
moteness from us, whence this star Is
| probably to be classed among those celes-
| tial giants which so dwarf our own splen-
did luminary.
Two Interesting Stars.
Alpha Cygni, Vega and Affair form
frfan0io fha Sides M
which are Of about equal length. Nearly
at the center Of this triangle stands Beta
| Cygni. in the foot Of the Cross--beak of
the Swan. Beta Cygni Is one Of the very
finest Of the colored double stars, and Is
splendid object for q small telescope.
an ordinary spy-glass or even a good field
glass. The principal star Is yellow; the
smaller companion Is of deep marine
blue.
Beneath and at the right Of Alpha Cyg-
nj forming with 1t and the lower two stars
in the arm Of the Cross four-sided figure
| with nearly equal sides, stands the ia
| nous star 81 Cygni. interesting as the first
distance from US. to Bessel. some sixty
years ago. The star is of about the fifth
magnitude, of a decided orange color. It
Is the uppermost Of three stars-two q
tride brighter than itself-with which It
forms a quite noticeable little triangle
Even a small telescope shows 1t to be dou-
BILE. consisting OF two components Of the
same orange color and Of about equal mag
nitudes. The distance Of 61 Cygni as 1t has
| been determined independently by several
observers, who have reached substantially
the same results, Is In round numbers 40
| m1llion-million miles To traverse this dis
tance light requires about seven years
The combined mass Of the two bodies which
form the double star Is probably rather
less than one-half that Of the sun. Re-
moved to their distance. the sun would
oh fnA fCu cfny 1f Oh A. ls-
magnitude. The most striking fact in the
case, however, Is that. although to the
| naked eye and even through q field glass
| these two luminaries appear as a single
star, their actual distance apart is not
less than 5000 million miies-twice the dis
tance Of the planet Neptune from the sun
Only one other star, so far as Is known, is
nearer to us than 81 Cygni This star is
double star situated too far south to be
| visible to an observer in the mean latitude
| of the United States. The distance of this
star, according to Drs. Gill and Elkin is
about four and one-third light years." ST.
rtus. once assumed because of it's superior
brilliancy to be the nearest of the stars,
| Is distant from us about nine light years
Rich I'm Stars.
Lying in the thick Of the Milky Way
the Swan Is one OF the richest of the con-
stellations in stars visible or invisible to
the naked eye, It Is for this reason an es-
an opera glass. particularly the region in
the neighborhood Of the star Alpha. To
discover its full richness requires, OF
course. large telescope or. better, the
The most effective way OF observing this
region OF the heavens through telescope
Is to sweep" It slowly and watch the
golden shower of stars which falls conttn-
ually through the field Of the instrument,
stars OF all magnitudes down to those SO
tiny as to suggest an almost impalpahle
diamond dust sprinkled on the face OF the
sky. The question which naturally occurs
to the observer is Are these myriads OF
stars all suns. comparable in size with our
own grand luminary. and II they are suns,
at what distance must we conceive the
great mass Of them to be In order that
These are questions which astronomers
are still unable to answer, and upon which
views are held that are quite discordant
with one another.
The elder Herschel assumed that all the
stars of the Milky Way were suns, and
upon this assumption he based his disc
theory" OF the general shape Of the stellar
universe. On this theory the stars extend
much farther In the plane OF the Milky
Way than in the direction perpendicular to
this plane. The stars are faint, In some
cases at least. because of their unthinkable
distance from US. and their crowded OPP
pearance Is an optical effect due to the CIR
cumstance that from our point OF view
near the center OF the grand disc we look
we face the Milky Way than when we face
In direction at right-angies with Its
plane. There are many considerations
which render Harsehers view improbable.
and, indeed, he himself practically aban-
doned 1t In his later years.
shown by Photography.
Recently photography has brought its
powerful aid 70 bear upon this question.