Bristol news. [volume] (Bristol, Va. & Tenn.) 1867-189?, 1872-07-30
SCIENTIFIC.
GREAT NEWS FROM THE STARS.
Important Discoveries by DIR,
EfsEggins--The velocity OF the
Stars Measured by the Spec
tTosCepe- ReHa;,rEkabie facts
about Stars drifting tiar0ugil
&n.HnN

7 Astronomical Society, DIR. higgins,
/ thc eminent spectroScopist, made an
! extraordinary statement respecting
the motions taking place among the
! stars The results he announces are
50 wonderful that it will be well brief
! ly to explain how they have been Oh
tanned, as well rs their relation to what
had formerly been known upon the
| subject. Our readers are doubtless
aware that the stars are not really fix
ed, but are known to be travelling
! swiftly through space. 70 ordinary
/ observation the stars seem unmOYiag
| nor indeed can the astronomer recog
! niZe any signs of motion save by pro-
! lOnged observation. But if the exact
| place Of star he carefully determined
! at any time, and again many years Ia
! ter, n measurable displacement can be
| recognized; year after year, century
! after century, the motion thus deter
mined proceeds, until at length the
star may be removed by consIdera-
| Bile arc (Or what is so regarded 10y as
4 tTOnomerS accustomed to deal with the
minulcst dispIacements) from the po-
sition it had formerly occupied. But,
in general, these movements afford no
means of estimating the real
RATE AT WHICH THE STARS ARE
-. TRAVELLING
through space. In the first place a star
might be moving with enormous ra-
! pidity towards or from the earth and
yet seem 10 bc quite fixed on the star
! vauli-iUSt rs the light of a rapidly ap-
/ pToachiHg or reccding train seems 10
occupy an unchanging position if the
| trains course is at the moment in the
I direction of the line of sight. 1t is
only what may be called the thwart
motion OF the star that the astrOnO-
mCr can recognize by noting stellar
displacemcntS. But even this motion
hc can not eStimatC-in miles per sec
ond, say-unIcss he knows how far
off tho sun is; and astronomers know
/ in truth very little about stellar dis
tancCS. Now il seems ri first sight
altogether hopeless to attcMpti0 meas
ure The rate at which 4 star IS APP
preaching or Teccding. No change of
brightness could be looked FOR, nor in
deed could any observed change be
trusted rs an evidence of changed dis
tancc, since stars are liable TO real
.hangcs of bTilliancy, much as our
sun is liable to be more or less spot
marked. But
TIE DISTANCES OF TIE STARS
are so enormous that no conceivable !
rate of approach or recession could at- |
feet their brilliancy discernibly. Only |
the most rapid thwart-motions yet |
recognized would carry a star over a |
space equal TO the moons seeming di- |
amylcr in 500 years, SO that cores |
puuding motiol of recess or approach |
would only change a stars distance to |
about the same relative extent, and 1t |
is uhyioUs that such 4 change could |
not make star, even in that long pc |
riod, change appreciably in bright |
ness. 1t viii seem, then, utterly in |
credible that astronomers have learned |
not merely whether certain stars are |
receding or approaching, but have ac- |
tuallV been enabled TO determine res |
pccting this kind of motion what they |
can not determine respecting the more |
obvious thWart-mOtiOn, viz, the rate |
at which the motion takes place.
This is rendered possibly by what is |
known of the mature Of light. Light |
travels through space in waves, not as
a direct emanation. Now let us COM
pare Il stars action in emitting such |
waves with some known kind of wave
action, and we shall at once recognize
the
EFFECTS OF VERY RAPID MOTION on
THE STARS PART.
Conceive a fixed paddle-wheel turning
at uniform rate in water, and that
every blade as it reaches the water
raises one wave, that wave being
transmitted in a given direction. Then
there would be n succession OF waves
separated from each other by 4 con-
slant distance. But suppose the pad
dle-whecl itself 10 be carried in the
given direction. Ii is clear that after
one blade has raised its wave the next
blade, descending in the same time as
before, will reach the water closer to
The preceding wave than if the pad
die wheel had been at rest; for the
moving wheel have carried the blade
closer, so that now a succession of
waves will result as before, but they
will have their crests closer together.
And obviously, if the wheel were car
ried in the contrary direction, the
wavc-crests would be further apart
than if the wheel had been at rest.
Thus reverting to the stars, We infer
that, if q 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 vice
versa. Now the distance between the
of light signifies a dille-
renee of color, the longer waves pro-
ducing red and orange light; waves of
length. yellow and green
li"rit and the shorter waves produce
ing blue, indigo and violent light. So
that if a star were shining with pure
red light, it might by approaching |
very rapidly bc caused TO appear yell
low or even blue or indigo, According
TO the rate of approach = while II a
star were shining with pure indigo
light, it might by recedinS very rapid
~ be caused to appear green or yellow,
Or even oraage or red. But stars do
not shine with pure colored light, but
with a mixture of all the cOlors of the II
rainbow; so that the attempt TO esti-
mate a stars rate of approach; or re-
,essiop by its color would fail, even
though we knew the stars real color
md color-changcs. The spectToScop-
ST has, however, much more deli
,ate means of dealing with the matter.
The raiDbow-tinted streak forming a
,tar's spectrum is crossed by known
lark lines; and these serve as 5
1ERITABLE MILE-MARKS FOR THE {
SPECTROSCRoPIST.
If one of the lines in thelspeetrum of ,
my star is seen TO be shifted toward :
he red end, the observer knows that
he star is receding, and that swiftly
4 the shift is toward the violent end,
Ie knows that the star is swiftly alr
preaching. Now, Dr. Higgins has
,een able nearly fom years ago TO aI-