The Elk County advocate. [volume] (Ridgway, Pa.) 1868-1883, 1872-09-12
The Motions Of the Stars.

1t will seem utterly incredible that
astronomers have learned not merely
whether certain stars are receding or ap-
preaching, but have actually been en-
abled to determine respecting this kind
of motion what they cannot determine
respecting the more obvious thwart- mo-
ii on, viz, the rate at which the motion
takes place This is rendered possible
by what is known of the nature of light.
If star is approaching, the light which
comes to us from it will have its waves
closer together than if the star were at
rest, and rice gerSa. Now, the distance
between the wave-crests of light signifies
a difference of color, the longer waves
producing red and orange light; waves
of medium length, yellow and green
light and the shorter waves producing
blue, indigo and violet light. So that,
if u 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.
But stars do not shine with pure COL
ored light, but with mixture of all the
colors of the rainbow; so that the attempt
to estimate stars rate of approach or
recession by its color would fail, even
though we knew the stars real color,
and even though stars moved fast enough
to produce color-changes The spec
troscopist has, however, q much more
delicate means of dealing with the mat
ter. The rainbow-tinted streak forming
a stars spectrum is crossed by known
dark lines; and these serve as veritable
mile-marks for the spectroscopist. If
one of these lines in the spectrum of any
star is seen to be shifted toward the red
end, the observer knows that the star is
receding, and that swiftly; if the shift
is toward the violet end, he knows that
the star is swiftly approaching.
Now, DR.. Hugglns had been able
nearly four years ago to apply this
method to tie case of the bright star
Sirius, though his instrumental means
were not then sufficient to render him
quite certain as to the result Still he
was able to announce with some degree
of confidence that Sirius is receding at a
Idle chCeeulilS IWohly HllleS per second.
In order that he might extend the
method to other stars, the Royal Society
placed at his disposal a fine telescope,
fifteen inches in aperture, and specially
adapted to gather as much light as posi-
BILE with that aperture. Suitable spec
troscopic appliances were SO provided
for the delicate work DR.. Huggins was
to undertake. 1t was but last winter
that the instrument was ready for work
but already DR.. higgins has obtained
the most wonderful news from the stars
with its aid. He finds that many of the
stars are travelling far more swiftly than
had been supposed. Arcturus, for ex-
ample, is travelling toward us at the rate
of some fifty miles per second, and, as
his thwart- motion is fully as great (for
this stars distance has been estimated),
the actual velocity with which he is
speeding through space cannot be less
than seventy miles per second. Other
stars are moving with corresponding
velocities.-Popular Science Monthly for
September.