Evening star. [volume] (Washington, D.C.) 1854-1972, 1899-11-04
THREE NORTH STARS
Some of the Wonderful Results of Spectre
scopio Observation.
Explanation of the Use of the Instru-
ment in Revealing the Presence of
Invisible Heavenly Bodies.
From the Boston Evening Transcript.

Northsstar. So close and faint is this COM
panior1 that owners of small telescopes have
often used 1t to test the power of their
eyes and Instruments News has lately
come from the Lick observatory at Mt.
Hamilton. California, of the discovery that
Polarls consists of three stars, two of
winch reVoiVe around common center of
gravity in about four days. At the same
time these two revolve around a third star
III much the same way as the earth and
moon revolve around the sun. In this case
the test is so severe that no telescope can
see the individual stars. We can only in
fer their existence by noticing a peculiar
phenomenon in the spectrum of Polaris
The stars, and in fact all luminous bodies,
emit a series of waves which are trans
mitted by the ether to US. Those waves
that fall upon the retina of our eyes pro-
duce sensation that we call light In the
case of many millions of stars the effect of
these waves upon our eyes is inappreciable
Without the aid of some instrument such
stars are invisible. The lens of a telescope
condcnSeS a large area of waves into a
small compass, and this increases the eff
1ect upon the eyes of tho observers Con-
seGuefitiy telescopes with large lenses can
gather III so much light as to make exceed
lI%lE liant stars visible to the observer
but uSht fas another characteristic be-
sues lntensity-that is, color. When a GER
tain number of waves enter the eve each
second we call the resulting sensation red
w men larger number enter each second
we call the sensation violet etc If the
light gathered by some large telescope pass
e. through a prism, or better, several
prlSms, the different colors are arranged
Ill the order Of their wave length Such an
arrangement of colors has been named the
spectrum.
The spectrum of the sun and of most of
U
dark lines. These lines are really gaps
caused by the absence of rays Of light
OF certain wave lengths. The light before
it can reach our telescope. has 70 mass
through extensive solar atnosnbere
WElCh absorbs certain parts The eans in
the spectrum caused by atmospheric all
Scrptlon of the sun and stars are called
lines. ~ et''-e"
When a luminous body is at rest the
waves OF light are emitted in all directions
ankle But when it is moving RAPIDLY the
waves IN front are crowded, while those in
the rear are correspondence heightened
OF course, al the sides the waves contin,In
70 De emitted at their normal wave length
Inc same phenomenon is exhibited in
sunni. II an express train whistles as it
passes the pitch of the whistle is DerceDti
bly, lower when the train is recedine than
Mileh II Is approaching. Therefore, when
tle star Is approaching the earth with n
SulIclentiy large velocity all the lines are
Glspiaced trifie toward the violet thar
belng the color with the shortest u,aZre
4tilSth. conversely, when the star is re-
cedlHg from the earth the lines are dis
!l1acSo toward the red end of the spectrum.
Inns displacement is so exceedingly cIigbt
ihat measurements of its amount have rad
4itHe EaIue until recently. The first sue
ISL investigation on the motion in the
..ne 81 5!sht was upon the rotation Of the
sun by NoBef in 1871. Since then the snnc
ira nave been photographed and maasIIred
IN THIS way displacements corresnondino
~ d Selocily considerably less than a mile
per second can be detected.
III two stars are SO close toretbar .ho4
they appear in the Telescope as single Oh
Ject, the Spectra will be superimposed So
long as these two stars move away from
u.s. VI toward US at the same rate. the lines
III inns compound spectrum will cOntiuue tn
MAINTAIN the same relative positions Rnt
IL the Two compOnents of a double star
move IN opposite directions in such a wav
Iii'l one Is approaching while the other is
fecedlnS from the EARTH then the lines Of
the two supcrimpOSed spactra will he A.
placed In opposite directions Sometimes
only one Of the components of ninary
star IS bright enough to be seen. AS this
star feFolVeS around the center OF gravity
between 1t and its dark companion II IL
sometimes approaching and sometimes re-
cedlhg from the earth. The lines of ite
ward the violet and then toward the rcd
emu Oh the spectrum. Hence when a star
IS FOUND whose motion in the line OF SIGHT
- variable, 1t Is Justiffable TO conclude that
S-t"t - |LtSS " II d FAINTER Communion Tho
PERIOD OF revolution Of such bodies about
tleIr center OF gravity Is, of course Obtain
ed directly from the observations
IN 1881 photograph taken at the Har-
EdIu coliege observatory of the spectrum
OF Zeta Crsae Majoris (the middle star In
the handle OF the DippeD was found TO
contain several double lines An e.amina
Ion, lioh OF the photographs showed that the
iihe9 are sometimes double and sometimes
single. Evidently we have here q double
star whose comDOnents are so close "a
gether that no telescope can show them as
double stars. They are revolving around q
common center of gravity in such n nIane
that when one is appro aching the orhrr is
recehng from the earta. Twice durinp,
every revolution they are nearly in a line
with the earth. They are then ncitber m
preaching nor receding, the lines Of thair
gle. ''i 84'i-
Beta Persei, named Algol, furnishes an
example of q binary star where only one
of the compOnents is visible Vogel, at
Potsdam in 1883. found from the displace-
Hitht or the lines in the spectrum that AL
Sol IS moving IN a small orbit at the rate
OF tWenty-SlX miles per second. To ac-
count for this it is necessary to assume
that there is a dark body, and that A .gol
and It's companion are moving around a
common center of gravity. In this instance
the existence of the dark companion is
still further demonstrated by the yaria-
ton in AlgolS light. GOodrcke in 1872 dis
covered that Algol was variable star 1t
- HSuhliS toilStdul IN brightness, but at
times it VIII decrease in light for few
hours and then in d few hours more regain
ats normal brightness. These minima in
Hght occur with great regularity, the pc
Ilod being little less than seventy hours
Sucn phenomenon naturally suggests
partial eclipse caused by some dark body
periodically passing between us and the
star.
10y means of the enormous Hght-gather-
ing power of the Lick telescope thirty-six
iilcheS aperture) PROF. keeler has been able
10 measure the velocity in the line of
s!ght OF the Great Orion nebua. He finds
that 1t Is receding from the earth at the
rate OF about eleven miles per second
y, nile at the Allegheny observatory Prof.
keeter used this same spectroseopic method
10 prove that Saturn's rings are neither
solid nor liquid. They consist of small
bodies That revolVe around Saturn
SpectroScopic determinations of motion
In the line Of sight is one of the most prom
lslng fields Of investigation in astronomy
Many problems have been solved that for
centuries have seemed hopelessly beyond
our reach.
A Graveyard of Prehistoric Dwarfs