The Portland daily press. [volume] (Portland, Me.) 1862-1921, 1899-09-30

II two stars ore 50 Close together that
they appear In the telescope a. a iIipgIs
object, the speetrn IL superimposed. SO
long as these two stars move away from
Us, or t0wHri Us at the Same rate, the
lines In this compound spectrum will con-
tlBue to maintain the same relative posi-
lions. But II the two eemponents Of a
double star move In opposite directions
10 such WAY that one - approaching
while the other IL Fsceding from the
earth. then the lines of the two supsrim-
posed spectra will be displaced in oppo-
sips direotiona. Sometimes only one of
the cOInp0uents OF q binary star IL bright
enough 60 he seen. As this star reuolves
around the ce1trs Of gravity between 10
aDdsits dark companion ft Is sometimes
9pproacbfug and sometimes recsdtng from
the earth. The lines Of it's spectrum are
therefore displaced first toward the violet
and then toward the red end Of the spec
trum. Hence when star Is found whose
motion In ths line of sight II variable, 10
IL 1usuiiabls to conclude thns there is
closs 10 10 n fainter companion. The
period OF revolution tf such bodies about
tnelr centre OF gravity is, CT course,
obtained directly from the Observations
In 1887 photograph taken &C the Har-
ward College Observatory OF the spectrum
OF lsta UrfR Majoris 1.-THE middle star In
the handle OF the Dipper) was found to
contain several double lines. An exami-
nation OF the photographs showed that
tne lines are sometimes double and some
times single. Evidently we have here a
double star whose componsDts are so cIo9e
together that no telescope can show them
as double stars. They are revolving
around a common centre of gravity in
such plane that W hen one Is approach
ing the other is receding from the earth.
Twice during every revolution they are
nearly in II line with the earth. They are
then neither approaching nor rsceding,
the lines OF their spectra are In juxtaposi.
tion and appear single.
Beta Persei, name A1gol, furnishes an
example of q binary star where only one
OF the components Is visible. Vjgei, at
Potsdam In 1888, found from the displaee-
msnt Of the lines in the SPECTRUM that
Algol Is moving In small srblt at the
rats OF twenty-six miles psr second. To
account for this 1t Is necessary to assume
that there Is dark cody, and that AIgol
and It's companion are moving around
common centre of gravity In this in
stance the existence OF the dark compan-
ion is stiIl further demonstrated by the
variation In AlgoPs light Goodbrlcke
In 1852 discovered that AIgol as varia-
bic star. IL Is usually constant IN bright
ness, but at times 1t will decrease in
light for few hours and then in a few
hours more regain its normal brightness.
These minfma in Hight occur with great
regularity. the period being little less
than seventy hours. Such phenomenon
naturally suggests a partial eclipse
caused by some dark body periodically
passing between US and the star.
BY means of the enormous Iight-gather-
ing power Of this Lick telescope (thirty-
six inches aperturel Prof Keller has
cen able TO measure the velocity In the
line Of sight Of the Great Orion Nebula.
He finds that it Is receding from the earth
Mt the rate OF about elaven miles per sec
ond. While at the ALE lhany Observatory
Prof. Kesler used this same spectroscopio
method TO 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
promising tields OF Investigation In as
tronomy. Many pro blems have been
solved that for centuries have seemed
hopelessly beyond our reach.