Dodgeville chronicle. [volume] (Dodgeville, Wis.) 1862-current, 1874-10-09
Distances. of the Stars.


our idea of the universe has undergone
complete metamorphos1s, though but few
persons appear to recognize TINS TACT.
Less than century ago the s00GntS who
admitted the earths motion (some still
rejected it) pictured to themselves the
system of the universe as being bounded
by the frontier of Saturn's orbit, at dis
lance from the central sun equal to 109,-
600 the diameter of the earth, or about
960,000,000 miles. The stars were fred,
specifically distributed at distance but
little greater thansthat of Saturn. Be-
You'd this limit vacant space was sup
posed to surround the universe. The
discovery of Uranus, in 1886, did away at
once with this belt, consisting of Sat
urn's orbit, and the frontier of solar dom
nation was pushed out to distance of
100000 900 miles from the center of the
system, that is to say, beyond the space
which was vaguely supposed to be occu-
pied by the stars. The discovery of
Neptune, in 1916, again removed these
limits to distance that would have APP
palled our fathers; the orbit described
by this planet being 2,862,000, 900 miles
frOmlthe sun.
But the attractive force of the sun ex-
tends further still. Beyond the orbit of
Uranus, beyond the dark route slowly
traversed by Neptune, the frigid wastes
of space are travelled over by the comets
in their cratic courses. Of these, some,
being controlled by the sun, do not leap
from system to system, but move in
closed curves, though at distances far
greater than those of Uranus and Nep-
tune. Thus Halley's comet recedes to a
distance Of over 1920, 100000 miles from
No ~ 000 mn 000
and that of 1850 75,000,000,000. The
period of the last-named comet is $500
years.
Still these figures can scarcely be COM
pared to those which represent the dis
tances of the stars. What means have
we of measuring these distances? Here
the diameter of the earth will not serve
as the base of the triangle, as when we
measure the moons distance; nor can
we, as in the case of the sun, get any as
sistance from another planet. However,
fortunately for us, the arrangement of
our system affords us q means of meas
uring these distant perspectives; and
this, while demonstrating over again the
earths motion round the sun, turns that
motion to account for the solution of the
greatest of astronomical problems.
In revolving round the sun at the dis
lance of 100000 900 miles, the earth an
nually describes an ellipse of about $780,
100000 miles. The diameter of this orbit
is 1874, 100000 miles. AS the earth's rev.
OlutiOn round the sun is performed in a
year, the earth at any given instant will
be opposite to the point where it stood
six months before, as also to the point
where it will stand six months later
Here is line Of sufficient length to serve
as base of a triangle the apex of which
shall be star.
The process, then, for measuring the
distance of star from the earth consists
in Infinitely observing this star at an in
terval of six months, or better for whole
year, noting whether it remains fixed or
whether it undergoes some little appre-
cable displacement of perspective, owing
to the annual displacement of the earth
around the sun. If it remains fixed, this
is BECAUSE it is an infinite distance from
us-at the horizon of the heavens, so to
speak-and our base-line of $4,000, 900
miles is as nothing in comparison with
this remoteness. But if it is displaced,
then we know that it annually describes
small ellipse, corresponding to the
annual revolution Of the earth. Every
one has remarked, while travelling by rail,
how the trees and other objects near at
hand move in a direction contrary to
our own, their speed being greater in
proportion to their nearness; whereat
distant objects on the horizon remain
fixed. The same effect is produced in
space, in consequence of our annual
motion round the sun. But though we
move incomparably swifter than an
express train, our rate being $685., 900
miles per day, and $4,000 per hour, the
stars are so distant that they scarcely
bulge. Our 284, 100000 miles of dis
placement are almost nothing as con-
Germs even the nearest of them. The in
habitants of Jupiter, Saturn, Uranus, or
Neptune, with their orbits five, nine,
nineteen, and thirty times as large as ours,
could determine the distance of far
greater number Of stars than we.
This mode of measuring the distance
Of the stars by the perspective effect
produced by the earth's annual displace-
ment was anticipated by the astromo-
mers OF the eighteenth century, and in
particular by Bradley, who, while at
tempting to measure the distances of
the stars by comparing together obser-
vations made at an interval of six
months, iscovered-something else.
Instead of finding the distance of the
stars on which his observations were di-
rected, he discovered a very important
optical phenomenon, viz, the alteration
Of light, the effect produced by the mo-
ton of light and the motion of the
earth combined. Similarly, William
Herschel, while seeking the parallaxes
OF the stars by comparing bright stars
with their nearest neighbors, discovered
the systems of double stars. So, too,
Fraunhofer, while seeking the limits of
the colors in the solar spectrum, dis
covered the absorption rays, the study of
which has given rise to spectrum analy-
sis. The history of the science shows
that frequently discoveries have been
made in the course of investigation which
had but little to do with them directly.
Columbus discovered the New World
while aiming to reach the eastern coast
of Asia by sailing to the west. He
would never have discovered it, would
never have sought for it, had he known
the true distance between Portugal and
Kamtchatka.
1t was not until 1910 that the distance
of any of the stars was ascertained. This
discovery is therefore of recent date, and
we are only now beginning to form an
approximate idea of the real distances
which separate us from the stars. The
parallax of the star sixty-one in the
Swan, which was the first to be deter.
mined, was ascertained by Bessel. and
was the result of observations made al
Konigsberg from 1887 to 1910. In 1915
Arago and Matthew had made observa-
tions ON this star, but without reaching
any certain results. The parallax Of
Alpha in the Tyre was found by Strive
in the course of observations made al
Dorpat between 1885 and 1888; but il
was not published till after the wear 1910