The Hickman courier. [volume] (Hickman, Ky.) 1859-current, 1874-06-27
ARCTURUS.
What Astronomers Know About this
Typical Star.

sparkling mysteries of the northern
hemisphere. 1t is the fourth on the
list of the twenty frst-magnitude stars,
it's three more brilliant rivals, Sirius,
Campus, and pha-Centauri, being sit
uated 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 charac. eristic, and Arcturus,
besides being the leading brilliant of
the north, bears 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-
ey. Even the most powerful telescope
reveals nothing like a disk in these in
tensely luminous points. But, if the
same stars are subjected to the delicate
analysts 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 so thoroughly by Secchi and other
astronomers that 4 regular and partial
ly exhaustive classification has been ar
ranged, including all the stars that have
| been observed. It 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 q pre-
/ yious 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 more advanced stage of
condensation.
Arcturus is che typical star of the
second class, or yellow stars. This
class is specially interesting to terres-
! trial observers as tn, one to which our
| sun belongs. Its spectrum compares
/ perfectly with the solar spectrum. Not
only have the dark lines that cross 1t
| 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-
| ton, have incandescent.. PHILOSOPHERS,
and are surrounded by atmospheres of
! heated vapor that absorb the same rays
| of light which they would emit if they
vert, 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
/ a terrestrial substance, we may conclude
| that this element is present in the at
mosphere of tAe star. In this wav it
| has been found that sodium, iron, by-
/ drOgen, magnesium, calcium, bismuth,
| and several other substances, exist in
Arcturus and its kindred stars, Just as
| surely as they form a portion of the
material of the earth and the SUM-
/ Thus does the spectroscOpe give mar
velous proof of its power in revealing
some of the constituents of a star so
far away that, when viewed from oppo-
site points OF the earth's orbit, 1S3, 600
| 900 miles distant, its position is not
sensibly changed to common observa-
ton. For it is only when examined by
practised eye, and a delicate measure
ment, where a hair's-breadth means
millions of millions of miles, that the
slight displacement is detected which
| gives the data for measuring the almost
| boundless space between the star and
the earth The 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 be
made with mathematical precision, for
! Sirius, though classed as a white star,
| has a decided blue tint Arcturus,
classed as yellow star, has an equally
| decided red tint; and the sun, 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 l, 624, 900 times 81, 430, 900 miles, and
| it takes light about twenty-six years to
| traverse the intervening space. When
we realize that the estimated error In the
suns distance of about $500, 900 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 uncomfortable distances the
SUMS distance from the earth is adopted
II
one second of a degree means that a star
is BOG, 265 times 81, 400, 600 miles away,
| and yet not star in the heavens shines
within this range of space, not a star
CLOVIS in the armament whose parallax
is not less than this infnitesimal por-
tion 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, a line 81, 430, 600
miles in length, would be hidden by a
thread an inch in diameter at distance
of six hundred and fifty feet I And yet
astronomers conquer these almost insur-
mountable difficulties, and tell us the
distance of tie bright orbs, whose
waves of light are borne to our little
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
impossible task even to measure the
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 hopeless undertaking, for the
stars are placed at distances so enor-
nous that no conceivable rate of APP
proach or recession can affect their APP
parent brilliancy. DR.. Higgins, the
idefatigable worker, has, however, been
able to solve the difficult problem with
his powerful spectroscope, by the aE-
plication of a simple and delicate test.
It is well known that light travels in
waves, and that change in wave-crests,
produced by approach or recession, is
indicated by color. If one of the dark |
lines in the stars spectrum is shifted |
toward the red end, the star is reced- |
ing; if toward thNyiolet, it is approach
ing. The lines in Arcturus are shifting
toward the violet end of the spectrum, |
and the star is approaching at the rate