Evening star. [volume] (Washington, D.C.) 1854-1972, 1899-09-02

SKIES N SEPTEMBER
Consultations That Are Now Above
the Horizon.
TIE NATURE OF DOUBLE STARS
Use Of Photography in Studying
the Milky Way.
PLANETS OF THE MONTH
PLANETS OF THE MONTH

Written for The Evening Star.
The principal consultations which are
now above the horizon at 9 pm. are the
Swan (Cygnus), or Northern Cross, direct
ly overhead; the Eagle, the Tyre Her.
cules, the Dragon (Draco), Pegasus and
the Dolphin Jobs Coffin). all grouped
about the Swan, as may be seen from the
planisphere; the Scorpion, Ophiuchus and
Sasittarius, in the southwest; Cassiopeia
Perseus and Andromeda, in the mort beast
and low in the northwest the Great Dpper
in the Ursa Major
The first-magnitude stars now visible at
the hour named are: Vega. in the Lyre
nearly overhead; Arcturus near the hor-
lion between west and northwest; Affair.
IN the Eagle, nearly south and at three
hfths of the distance from the horizon to
the zenith; Fomalhaut the eve of the
Southern Fish, low in the southeast; An
tares, the Scorpions heart" equally low
IN the southwest. and Deneb Cygni the
bright star which marks the head of the
Northern Cross. Within a half hour Ca
pella, the rival in brilliancy of Vega and
Arcturrs, will rise in the northeast
Inc bright yellow star seen in the south
west, some ten degrees above the ruddy
Antares. is the planet Saturn. Jupiter al
SO is now above the horizon in the early
evening, but sets before O'clock
The "Demon" star
From now on for several months the
famous veritahle star Algol-al-Ghul. the
'demon'-will be favorably situated for OBJ
serving. 1t is now at the hour of our OBJ
servation low in the northeast With the
aid of the planisphere it should be found
easily. Observe that it forms with Alpha
fersei, a second-masnitude star at the CEN
ter of Perseus. and Gamma Andromedae
Andromala ri
right-angled triangle
The popularity of this star is that after
SHINING for about two and a half days as
a star of the second magnitude it falls in
the space of about four hours to the fourth
magnitude, and in the course of the next
four hours it RECEIVERS its usual brilliancy
The cause of this remarkable behavior is
the fact that the star has a dark compan-
ION. or 5atellite. revolving round it in an
orbit set nearly edgewise toward us so
that periodically the dark body passes be-
tween the star and us and cuts off por-
ton of its light. That this is the case is
indicated by the perfect regularity of the
change which takes place in the stars bril-
llancy, and has lately been established be-
yond a doubt by the spectroscope. which
has shown that the star alternately APP
proaches US and recedes from u.s. just as it
should do upon the suppoSiton that it is
circlng in orbit the plane of which
passes very nearly through the earth.
A New Variable.
There are some ten or dozen variables
of the "Algol type'-that is stars which
shine for the greater part of the time with
an unvarying brightness. but at regular in
tervals pale to a greater. or less extent for
few hours while they are undergoing a
partial eclipse of their satellites. The lat
est addition to the list is a star in the
Swan of between the eighth and ninth mag
nitudes, and therefore beyond the reach of
the naked eye. The variability of this star
was discovered at Moscow during the past
year from an examination of Photographic
plates, on one Of which it was found to be
unusually faint. Its light change has since
been found to be recorded on a large num-
Der of the Harvard College plates. and
erins has deduced period of days i3
hours 10 minutes seconds with an I'M
certainty which probably does not exceed
one or two seconds" The variation in
brightness of this star amounts to about
three magnitudes, exceeding that of any
other star of the Algol type yet discov-
cred. The story of the discovery of its
variability is fair illustration of the serv-
ice which photography is now rendering as
tronomy in various ways.
A minimum of AlgoI will occur on the
18th of this month, at about 10 pm, and
another on the Nth, at about pm.
The Milky Way.
The Milky Way now passes at pm d.
rectly overhead, arching the heavens from