The sun. [volume] (New York [N.Y.]) 1833-1916, 1896-03-29

The changes in the light of the star seem to
have been first noticed more than two hundred
years ago: but it was the deaf mute, amateur
astronomer. Goodricke OF York in England.
who first thoroughly studied the peculiar be.
havior of the star. and In 1888 suggested the
explanation that has lately proved true.
The star Is now and then partly hidden or
eclipsed by n dark object which revolves around
it, and comes between 1t and the earth. 1t has
a dusky partner. aud the pair waltz swiftly
around each other once in sixty-nine hours.
Moreover. from the way in which the light
wanes and revives again, and the amount by
which it is reduced when the star is ~faintest, we
can learn many things about the size of the OBJ
scuring body. and the dimensions of its orbit.
Prof. Pickering Of Harvard College, who ex-
amincd the matter very carefully in 1880, con.
cluded that everything might be explained by
supposing that the dark star which produces the
'eclipses" has a diameter not quite four
as great rs that of Algol itself. and that in their
motion the two stars keep NJ an almost unchang-
ing distance, which is n little moro than three
times the diameter of Algol. Both stars move,
of course, the centre OF their motion being the
point between them where their weights would
balance their common centre or gravity" to
use the technical term; and the circle on which
the larger star moves is just about half as large
as that travelled over by the smaller, because
the bright star weighs u little more than twice
rs much as the other.
But this is not all. As Prof. Pickering left the
subject there was nothing To determine the real
size OF the stars. or the diameter o: the race
way. however, by which they might be found
! out If one could only make observations sum
| spcctroscopc, that wonderful instrument which
has almost reconstructed astronomy within the
last forty wears.
When we look at a star with the spectro-
scopc. wc see, instead OF astar. a marrow stripe OF
across it; and IL II star is coming toward US,
these lines are all pushed out of their natural
position "A little toward the blue end OF the spec:
trlfn, while II II Ia reCeuInR they ARE displaced
in the opposite direction. by careful measure.
whether IA star is moving toward or from us.
and how fast. Now for the application:
Dr. Nogel OF potsdam, in Germany first sue
| cecded in making the necessary observations in
1889. lie arranged an instrument with which
he photographed the spectrum OF the star in all
photographs under n powerful microscope ho
shnWeu th a., hr : s 1Hrn u rncea 'ng from os sntt
the tremendous rnte OF twenty,stx and a half
miles a second. while seyentscn hours after the
speed. We know, then, the circumference OF
the circle on which This star moves by simply
hours by its velocity ~ twenty-six and ~one-half
miles II second and all the Other dimensions OF
the figure follow easily from this.
Here are Vogel's results. which, however. are
not To be considered absolutely exact, but only
Probably Very nearly right. tho bright star being
designated as a and tho dark body as Is;
Distance between centres OF a and r., 2 '0S S3' 600 600 m mil:
h,am"t@r 81 4 .,'.''.. .,'.. ,,,'''''' ' ~" Zoo, 900 niIss
Velocity ~ u, So mites per second.
According to this, A is considerably larger
than the sun. AMI Il is n trite smaller; but from
the motion OF the bodies IL can 10 shown that
their united mass is only about twO-thirds that
of the sun, MD their density only One-f fourth as
great: 50 that they are much lighter than water
and cannot he solid bodies. but only heavy
clouds \ being much more brilliant than the
Gun, while Is. for some reason not yet deter
mined, is dark,
whose size "" know; AS for all the rest we can
only guess at their real magnitude. hut this Is not
all the strange story OF our star, observation
has made IT plain that the interval between It's
mlnima has been slowly changing for the past
hundred NrNrS. first lengtheuing. hut later short
euing. - that NJ present II il about six seconds
shorter than il was IN GOpdrlCka's time.
MIR Chandler ~ Cambridge hh- shown that
this effect runs through its changes In about $50
wears. and Cuu bn explained 10y surprising that
AlrOl md ~ Communion are hOth moving to-
gcthor an "A grrn; orbit, as large rs that OF
the planet Uranus, under tho attraction OF some
invisible body that controls TIA" movement.
There may be-, however, some uouht rs To TINS
/ explanations, since TlsserRnd, one uf the ablest
uf the French astronomers, shows that a very
different one IS possible, and perhaps more
'Aignl viIalways be memorable In the history
Of ns,rp .omy ~ tie first variable star whose
chaufr- prrr thoroughly studlcd and satisfRc-
turi,y rXlil ned, as being tn" Irst star whose
size ia, been measured, ana ms having nrsJ
muhr rrrttHp the eNi~tCUv' ~ Stars dark, and to
VS. invisible. but intimately connected with
brightly luminous p~Artner,.
There are about "A dozen other variable stara
which undergo changes Of the same sort ne
be long before we shall he able todeal with then
In an equally satisfactory manner