The Grenada gazette., 1889-01-31
VARIABLE STARS.
Interesting Talk About These
Heavenly Bodies.
The Causes Which Produce Their varia-
bility in Light and Color Can Only
BE Conf Fut-
ure Developments.

Few persons unacQnaintod with as
tronomy fail to express surprise on
first learning that there are stars in
the heavens whose light is variable.
Stellar variability seems at first sight
incompatible with the stable and eter-
nal character of the heavens, and gives
one the idea of change and evanescence
among the celestial bodies. But that
such fact should be associated with
the waxing old of the armament is the
result OF ignorance and preconcelved
opinion. as the phenomena OF variable
ity have probably been recurring with
undisturbed regularity for thousands
and thousands of years.
Several scores of these variable
stars, as they are called, are visible to
the naked eye, and their changes may
be watched by any one sufficiently
well acquainted with the face Of the
heavens; while, when we call in the
aid of the telescope, the suurus rup!uly
increase to hundreds. Indeed, it is
not too much to say that could the
millions and millions OF stars at pres
ont irnown To astronomers IA" 1'''5"''f""
to rigorous scrutiny. probably many
thousands would prove to be variable.
These marvellous objects present little
uniformity of character; they differ
from one another in magnitude, period,
and range of variation. Some are
very bright: others, even at their
maximum brilliancy, invisible to
the naked eye One changes SO
little that it is very din =
cult to determine its variability; an
other runs through a scale of luctua-
ton extending to five or six magnl-
tudes. In period, again, or the time
from maximum to maximum, there Is
the utmost variety. Some complete
Lneir cycle OF ehauasa7 In n w days;
others occupy many mgnatIa several
have been steadi decreasing in light
within historic t.;@,. h!le with tenn
porary star" 1@f #naFance is Sc
rare, and ol n.a @. ahservation 50
limited, That Il - ,Hp, sible to say
whether their rnpr,grs occur period
ically, or whether the sudden Increase
OF splendor is to be regarded IL he
announcement of Il stellar catastrophe.
The space at our disposal is much
too limited to give an account even OF
the most important Of these objects,
but we may perhaps be allowed to dra"
attention briefly to two of the mos
rapidly variable in the northern heav
ems. The more conspicuous OF these
is situated in the constellation of Per
seus, and was known to the old astron
omers by the name of Algol, or The
Demon. For about two days and thir
teen hours this object remains quit
steady as an ordinary second-magni
tude star, and during this time pre-
sents no appearance OF popularity. A
the end of this period, however, i
suddenly begins to diminish in splen
dor, and goes on fading till, IN three
hours and half, it has decreased tt
the fourth magnitude. This brlllianc.
is retained for the remarkably shor
space of only eighteen minutes; an'
in another three hours and hal
the star has regained its orig
inal splendor. When one remem
bers that this object is not
mere light hung up in heaven, but al
immense luminary like our own sun
some idea will be gained of the mature
of the causes that are able to produce
such change. The other object, thougl
much fainter than Algol, being, in fact
scarcely visible to the unaided eye, i
even more rapid in its fuctuation. !
is situated in the constellation Cepheus
but being an inconspicuous object, ha
not the honor Of popular name. Thi
is the most rapid variable known. 1t
range, like that of Algol, is n littl
over two magnitudes; but its rate G
diminution is nearly twice as rapid, a
1t passes from the seventh to the mint
magnitude in two hours. The chang
Of light Is accompanied by remark
able change in color, the star bein
BLUSH at maximum and ruddy at min
mum, with intervening gradations.
What explanation have scientiti
men been able 70 give of these phe
nomenap At an early stage, 1t wa
suggested that diminution OF ligl
might be occasioned by the interver
ton Of a dark body, as u satellite, b
tween us and the primary; and In th