The Bossier banner. [volume] (Bellevue, Bossier Parish, La.) 1859-1952, 1879-06-05
The Distance of the Stars,

The Distance of the Stars.
Every one knows that some stars have
had their distance measured, and it i!
very commonly supposed that the same
is true of many, if not the majority, ant
that the determination of the distance i!
reasonably accurate. Nothing could bt
more erroneous. In the first place, as
tronomers have succeeded in getting re
suits only in about twenty cases, anG
with all but the nearest half-dozen the
uncertainty ranges from 10 to full 81
per cent. Of the whole distance.
In the case of the nearest star known,
CentGura, the distance of which is
about 100000 times our distance from
the sun, the uncertainty is perhaps not
much more than 5 per cent, if so much
but in the case OF the pole-star, which i:
twenty times as remote according to the
latest results, it is really doubtful wheth.
er its distance may not be as small as
only tenfold that of Centauri, or on
the other hand as great as forty or fifty
fold. We do not know, and can not find
out until our present means and meth
greatly improved.
This uncertainty, however, is not due
TO any coarseness or want of precision
OF astronomical as compared with other
scientific measurements; no more deli
cate or refined methods of observation
have ever been applied than those by
means of which the stellar distances
have been investigated. The difficulty
IS double; the quantity to be measured
is almost unimaginably small; and the
measurements, from the nature of the
case, can not be made at the same time
and under similar circumstances, but
only at intervals of several months and
under widely different conditions.
Now, what are the considerations
which will enable US to decide, as to
any particular star, whether it is prob
ably near or remote? They are princi-
pally two, and neither of them is abso-
lutely decisive.
In the first place, since the nearer a
star is to us the brighter it will seem,
we are justified in assuming that the
brighter stars, as class, are nearer
than the fainter, so that if star is
brilliant its proximity is to certain ex-
tent probable; but only probable, for
moments inspection of results thus far
obtained shows that several stars, so
faint as to be invisible to the naked eve,
are really nearer than Sirius.
A second, and on the whole more
valuable, indication of proximity is
found In the magnitude of what is tech
nically called the proper motion" of
a star. We find, by comparing obser-
vation' made at wide intervals of time,
that most stars "drift'' to a very OBJ
servable extent in the course of a cen
tury or two, this drift being due in part
to the motion of the star. Now it is
obvious, that, other things being equal,
II star were brought nearer, its ap-
parent motion in the sky would be
greater. And hence, Uice uersa, we NAV
INFER that those stars which show a rap
Id movement, are, as q class, nearer
than those which seem to be sensibly
stationary. At the same time, when
we come to comparisons between indi-
vldual stars. it is impossible to say that
Of two which appear to move at unequal
rates the faster is the nearer; for the
nearer may be moving, so to speak,
> head on" or at really less velocity
-han the remoter one.
In selecting stars for the inyestiga-
lon OF their parallax we must, then,
necessarily choose those which have
others apparently near them showing
10 signs of proximity to our system,
md we should give the preference to
hose which are either very brilliant or
nave considerable annual drift. There
IRE only few stars which fulfill all the
but those which do have
lot all been investigated, and there is
lere open an important field for the
abors of any who will take up the SUBJ
ect.
1t was just said that we must neces-
arlly select such stars as had other
reference stars near them.
he star Ceaataurs forms q single ex-
option to this general principle. Its
arallax OF nine-tenths of a second.
nore than twice that of any other known
tar, Is detachable, and was actually dis
overed by Maclear and Henderson in
oS1, not by measuring its position with
80 SHNo ~ ACiS IuOIlDg SLdTS, DtlU DIV
irect observations of it's right ascen-
ION and declination which refer its 20
tlon to the axis of the earth. When
ond tried to obtain the parallax of O
.yr1, some years previously, by similar
excavations at Greenwich, he came up
n the singular result of a minute mega
We parallax; that is, the star appeared
have a slight annual displacement
reclsely opposite to what it ought to
ave. This would locate the star. as
as been said, somewhere on the
her side of nowhere" or at a more
ian indefinite distance. Of course the :
iplanation, which Pond himself per-
city understood. is that the true paral-
x Is so small that it was covered up
I'd overwhelmed by the errors in the
iJustment of his instruments, varia-
1ns of the astronomical refraction, and
her causes due to the changing tenn
'rature of the seasons-Prof. Younq.
the Boston Journal of Cbentstru.
The London Metropolitan Board of
orks, after recent experiment on the
names embankment, finds that cleo