The Pulaski citizen. [volume] (Pulaski, Tenn.) 1866-current, 1874-07-02
ARCTURUS.
What Astronomers Know About thi
Typical Star.


hemisphere. 1t is the fourth on the
list OF the twenty irst-magnitude stars.
lts three more brilliant rivals, Sirius.
Campus, and Alpha Centauri, being sit
mated IN the southern hemisphere al
though Sirius is so near the equinoctial
that very many observers both north
and south can enjoy its peerless lustre.
Every prominent star has its distin-
gushing characteristics, and Arcturus.
besides being the leading brilliant of
the north, bears G marked resemblance
to our own great central luminary. its
spectrum being identical with the ordi-
nary spectrum of the sun. An observ-
er, Watching the stars, sees only twink
ling points OF light of varying brillian-
cy. Even the most powerful telescope
reveals nothing like a disk ia these IN
tensely luminous points. But, if the
same stars are subjected to the delicate
analysis of the telescope, a wide differ
ence is made manifest. They as natu-
rally fall into classes as plants fall into
genera and species, or rocks into peri
DDS and formations. The spectroscopic
analysis OF the stars has been carried
out 80 thoroughly by Secchi and other
astronomers that regular and partial
~ exhaustive classification has been ar
ranged, including all the stars that have
been observed. 1t is called "Secchi's
Star Types, and consists of four class
es the white stars including about one
half OF the observed stars the yellow
stars comprising one-third of the num-
Der: the variable stars numbering about
thirty and the red stars also number
ing thirty. We have already, in a pre-
vious paper, traced the chief character
istics of Sirius, the typical star of the
first class. All the members of this
class present an identical spectrum.
marked with broad and dark absorbent
lines. They take the highest rank
among the sidereal fraternity, and give
evidence of deeper philosophers, larger
masses, and a more advanced stage of
condemnation.
Arcturus is the typical star of the
second class, or yellow stars. This
class is specially interesting to terres-
trial observers as the one to which our
sun Belongs. Its spectrum compares
perfectly with the solar spectrum. Not
only have the dark lines that cross il
been compared with the solar lines but
Mr.. Higgins and Mr.. Miller. with in
finite labor, have compared the dark
lines IN the spectra of the principal
yellow stars with the bright lines of
terrestrial substances volatilized in the
electric spark. We know that the stars.
whatever may be their interior condi-
tion, have incandescent., PHILOSOPHERS.
and are surrounded by atmospheres of
heated vapor that absorb the same rsvs
of light which they would emit if thew
were self-luminous, and therefore we
may discover from the position of the
dark lines in the spectrum the sub
stances contained in the star. When
we find a complete coincidence between
these dark lines and the bright lines of
terrestrial substance, we may conclude
that this element is present in the at
mosphere of the star. In this wav il
has been found that sodium, iron, Nv
drogen, magnesium, calcium, bismuth-
and several other substances. exist in
Arcturus and its kindred stars, lust as
surely as they form a portion of the
material OF the earth and the sun.
Thus does the spectroscope give mar
velous proof of its power in revealing
some of the constituents of a star 40
far away that, when viewed from oppo-
site points of the earth's orbit. I83 -OOO-
600 miles distant, its position is not
sensibly changed to common observa-
ton. For it is only when examined bv
practised eye, and delicate MEASURE
ment, where hair's-breadth means
millions of millions of miles, that the
RANOCLACAAb 10 uGJGCL6U which
gives the data for measuring the almost
boundless space between the star and
the earth TheS yellow color of this
class of stars Is due to the fact that the
dark lines are less abundant in the
yellow portion of the spectrum. The
classification of the stars cannot he
made with mathematical precision. for
Sirius, though classed as a white star
has decided blue tint Arcturus.
classed as yellow star, has an eouallv
decided red tint /; and the sun, q yellow
star, is also variable star.
Arcturus is one of the nine or ten
stars whose distance has been approx
imately determined. It is estimated to
be J, 1924, 000 times 81, 430, 900 miles, and
1t takes light about twenty-six years to
traverse the intervening space. When
we realize that the estimated error in tbe
suns distance of about 8, 800. 600 miles
Is only equal in celestial measurement
to the apparent breadth of a human
hair at the distance of one hundred and
twenty-five feet, we can form some idea
OF the delicacy of measurement required
to obtain the distance of the stars
For these incCnceivable distances fine
suns distance from the earth is adopted
as the unit of measure. A psrallax of
one second of a degree means that a star
is 2O6, 265 times 81, 430, 900 miles awav-
and yet not a star in the heavens shines
within this range of space, not a star
glows in the armament whose parsllax
Is not less than this infinitesimal por-
ton OF degree It has been calcula-
ted that, to a spectator at Alpha Cen
tauri, the nearest star, the entire radius
OF the earth's orbit, line 81, 43O. 900
miles in length, would be hidden by a
thread an inch in diameter at a distance
OF SIX hundred and fifty feet And vet
astronomers conquer these almost insur-
mountable difficulties, and tell us tba
distance of the bright orbs. vbose
waves of light are borne to our IitAIe |
planet as the waves of a common ocean |
are borne to European shores.
But, if Arcturus is the fourth in |
brightness and theseventh in distance. It |
ranks first among the stars which have |
been examined in the velocity with which |
It is approaching the earth. It seems an 1
impossible task even to measure the 1
distance of the stars but, to determine
If they are moving toward us or from
us, is attended with still greater diff
Guilty. It was considered for a LONG
time as a hopeleBs undertaking, for the
stars are placed at distances so enor-
nous that no conceivable rate of an
proaoh or recession can affect their an
parent brilliancy. DR.. Higgins, the
Idefatigsble worker, has, however, been
able to solve the difficult problem with
his powerful spectroscope, by the ap-
Dlication of a simple and delicate test.
It is we'll known that light travels in
waves, aud that change In wave-erests,
by approach or recession, is
Indicated by color. If one of the dark
Ines IN the stars spectrum is shifted /
oward the red end. the star is reced- !
ng II toward the violet, it is approach {
oward the violet end of the spectrum. | !
nd the star is approaching at the rate !
( over fifty miles q second, or three :