Evening star. [volume] (Washington, D.C.) 1854-1972, 1895-03-30

in taking survey of these stars In the
light of recent investigation.
Sidereal astronomy is at work upon two
principal problems; first, what are the
stars and in what respects do they differ
one from another? problem attacked by
means of the spectroscope, and, second,
what are their distances from us? Sirius,
as the brightest of the stars, has naturally
figured prominently in these Investigations.
This star will be found tomorrow night
low in the southwest, and will be readily
identified from its superior brilliancy, esti-
mated at about five times that of an
average first-magnitude star. In the class
itication of the stars according to the char
acter Of their light, Sirius is a typical star
of the first class-a class which embraces
about oae-half of all the stars. The
'Sirian' stars shine with a bluish-white
light, and are held to be the hottest of the
celestial bodies. Their "spectra" indicate
the presence in their atmosphere of hydro
gen in great quantity. with only slight
traces of the vapors of the metals. They
are probably in an earlier stage of world
life than the yellow stars, which form the
second class, and which are nearly equally
numerous. The spectra of the stars of this
class, OF which our sun Is the most con-
spicuous member, are crossed by hundreds
of dark lines-in the case of the sun these
lines are reckoned by the thousand-which
indicate that their atmospheres are
charged with the comparatively cool vapors
CT the metals and the metalloids, while
the hydrogen lines are not especially
prominent.
1t is probable that the Sirian stars are
far less massive bodies in proportion to
their splendor than are those of the re-
manning classes. The discovery that Sirius
made by Mr.. Alvan Clark, in 1862, afforded
the means of determining the stars mass
that is, the amount of matter which it
contains-and it appears that while Sirius
Surpasses the sun seventy times in brill
fancy, 1t has no more than three times
the suns weight.
Capella, in the northwest at about two
hfths of the distance from the horizon to
order of brilliancy. Capella is a yellow
star, belonging to the second or solar,
class. Professor Vogel has recently stated
incidentally that a photograph of a small
section OF the spectrum of this star, taken
by him in his work of determining the
motions of stars '.in the line of sight"
showed no less than $50 lines-a fact which
should give the reader some idea, both of
the number of the lines of the spectrum of
bright star and of the nicely to which
stellar photography has been brought.
Arcturus, in the east at about the same
altitude as Capelia, stands on the scale of
strvatory IN this city one-tenth of a mag
nitude lower than Capella, although the
more common estimate makes it The
brightest star Of the northern hemisphere
This is also solar star.
Vega, or Alpha Lyrae, now just rising in
the northeast, is ranked on this scale as
the equal of Arcturus. Vega and Rigel, the
more southerly of the bright stars in Orion,
are both Sirian stars.
Procyon, the Little Dog. stands sixth on
our list. 1t will be found directly above
Sirius, with which and Betelgeuse, in the
right shoulder of Orion. it forms a large
equilateral triangle. Procyon is especially
Interesting from the fact that certain