The daily dispatch. [volume] (Richmond [Va.]) 1850-1884, 1872-08-26

Mor1oSs OF THE SrARs.--1t seems utterly
incredible that astronomers have learned not
merely whether certain star. are receding or
approaching, but have actually been enabled
TO determine respecting this kind OF motion
what they cannot determine respecting tne
more obvious thwart motion-yiz., the rate
af which the motion takes place. FMS IS
rendered possible BY what IL known OIL the
nature of light. ia star is approaching,
fhe light which, comes to us from it will have
he Waves closer together than If the star
wore A rest. and rice versa, Now, the dis
sance between the waye-crests OF Light sig
nifies a difference of color, the longer waves
producing red and orange light; waves OF
medium length, yellow and green light; ana
the shorter waves producing blue, mango, anu
violet light. So that If star were si'n!ns
with pure red light it might by approaching
very rapidly be caused to appear yeiio", OF
even blue or indigo, according TO tne rlle o.
approach, while II a star were SHINING VIII
the pure indigo light 1t might bs receuthg
very rapidly be caused TO appear green oi
yellow, or even orange or req.
R,,t stars do not shine with pure-colored
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 fall even though we knew tile
stars real color, and even though stars
moved fast enough TO produce color-changes.
The spectroscopist has, however, mucn
more delicate means of dealing with the mat
ter. The rainbow-tinted streak forming q
stars spectrum is crossed by known dark
lines and these serve rs Heritab!e 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 recediDg, and that
swiftly; IL the shift is toward the violet end,
he knows that the star is swiftly approaching.
Now. DR.. Higgins had been able nearly
four years ago to apply this method TO the
t.ase Of the bright star Sirius, though his in
strumental means were not then sufficient TO
render him quite certain as to the result.
Stili he was able to announce with some de-
gree of confidence that Sirius is receding ut
rate exceeding twenty miles per second.
In order that he might extend the method
to other stars the Royal Society placed at his
disposal fine telescope, fifteen inches in
aperture, and specially adapted to gather as
much light rs possible with that aperture.
Suitable spectroscopic appliances were also
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 stnls with its aid.
He finds that many of the stars are travelling
fur more swiftly than had been supposed
Arceurus, for example, is travelling toward
us at the rate of some fifty miles per second,
and as his tl,wart motion Is fully as great
flor this stars distance has been estimated),
the actual velocity with which he is speed
ing through space cannot be less than seventy
miles per second. Other stars are moving
with corresponding velocitics.-From Popu-
Tar Science Monthly for September.