Dodgeville chronicle. [volume] (Dodgeville, Wis.) 1862-current, 1872-09-27
Motions Of the Stars.


The stars are Often spoken of as fixed,
by which is meant thai they have no ap
parent motion except that due to the ro-
tation of the earth about its axis. 1t is
to this apparent immobility that the &C
curacy of many astronomical determine
tions is due; for instance, the determine
ton of the error of chronOmeter. But
the stars are not really fixed. Astrono-
mers have long known that they are NOV
ing through space, many of them with
great rapidity. These 21r0per motions, as
thew are called, can only be determined
nv prolonged and careful observation
and the rate of motion cannot be deter
mined by ordinary means, since the true
stellar distances are practically unknown.
Moreover, if the star be moving directly
toward or from the earth, we are Of
course, by ordinary observations, utterly
unable to detect it's motion
Under these circumstances we cannot
but regard the extraordinary determine
tions reported recently to the Royal AS
Economical Society by the eminent English
astronomer, DR.. Higgins as among the
most remarkable scientific triumphs of
the century. The statement seems at first
almost incredible; but it is nevertheless
true, that by means of the spectroscope
DR.. Higgins has succeeded in determin-
ing, not only whether certain stars are re-
ceding or approaching the earth, but also
the rate of motion at which they are
moving.
For the details Of the method by which
these determinations are made we are in
debted to an article in the Spectator which
is republished in the Popular Science
MonthIy These wonderful results are
arrived at through what is known of the
nature of light. Light travels through
space in waves. Now, if we compare
stars action in emitting such waves with
some known kind of wave-action, we
shall at once recognize the effect Of it's
very rapid motion. Conceive a paddle
wheel turning at uniform rate in water
Every blade as it reaches the water pro-
duces one wave, that wave being trans
mitted in a given direction, and there
would therefore be succession of waves
separated from each other by a constant
distance. Now, if we suppose the pad
dle-wheel itself to be carried in the given
direction, it is clear that after one blade
has raised it's wave, the next blade, de-
scending in the same time as before, will
reach the water closer to the preceding
wave than if the paddle-wheel had been
at rest; so that now succession of waves
will result as before, but they will have
their crests closer together. If the wheel
were carried in the contrary direction, it
is obvious that the wave crests would be
farther apart than if the wheel had been
at rest.
Now, reverting to the stars, we infer
that if star is approaching, the light
which comes to us from it will have it's
waves closer together than if the star
were at rest, and 0ice CerS0. Now, the dis
lance between the wave-crests of light in
dicates a difference of color, the longer
waves producing red and orange light;
waves of medium length, yellow and
green light; and the shorter waves, blue,
indigo and violet light. Hence, if a star
were shining with pure red light, it might,
by approaching very rapidly, be caused
to appear yellow, or even blue or indigo,
according to the rate of approach; while,
if star were shining with pure indigo
light, it might, by receding very rapidly,
be caused to appear green or yellow, or
even orange or red.
Stars, however, do not shine with pure
colored light, but with a mixture of all
the colors of the rainbow; so that we
could not estimate a stars rate of ap-
proach or recession by its color, even
though we knew the stars real color, and
produce cOlor-changes. The spectroscope,
however, furnishes us with wonderfully
delicate means of measurement. The
rainbow-tinted streak forming a stars
spectrum is crossed by known dark lines;
and if one of these lines is seen to be
shifted toward the red end, the observer
knows that the star is swiftly receding; if
the shift is toward the violet end, he
knows that the star is rapidly approach
i1g
Nearly four years ago DR.. Higgins APP
piled this method to the bright star Sir
ius, and although his instrumental means
were not all that could be desired, he was
able to announce its recession at rate
exceeding twenty miles per second. The
Royal Society has since placed at his dis
posal fine telescope, of fifteen inch aper-
ture, provided with all the necessary APP
planes; and although the instrument
was not ready for use until last winter, he
has already obtained with it the most re-
markable results He finds that many of
the stars are travelling far more swiftly
than had been supposed. Arcturus, for
example, is travelling toward us at the rate
of about fifty miles per second, and as his
apparent motion (as seen from the earth)
is estimated to be fully as great, his actual
velocity cannot be less than seventy miles.
per second. Other stars are moving with
corresponding velocity.
Amid these motions DR.. Higgins traces
the signs of law. He finds tendency
among the stars in one part of the heav-
ems to approach the earth, while the stars
in the opposite part of the heavens are re-
ceding from us. The stars which are ap-
preaching lie ON that side of the heavens
toward which the sun is travelling. There
are, however, stars which do not obey
this simple law; and among these, DR..
Higgins recognizes instances of that com.
munity of molten to which the name Of
stGr-dryt has been given; thus confirming
in the most remarkable manner a theory
which has hitherto rested upon theoreti
cal basis.
1t is impossible to predict what future
revolutions may result from this new
method of investigation; but the discov-
cries already made show that we have
gained great addition to our means of
scientific research. Christian Union.