Juniata sentinel and Republican. [volume] (Mifflintown, Juniata County, Pa.) 1873-1955, 1875-01-06
Twinkling Ofthe Stars.

The subject of the twinkling of stars
has engaged good deal of attention OF
late years, and some interesting results
have been obtained. A few years ago
the Italian astronomer, Respight, an
nounced the discovery of the cause OF
scintillation, in certain dark bands
which we're seen to traverse the spectrum
Of Q star, indicating changes in the re-
frsgibility of our atmosphere, from hot
and cold strain, which produce some
thing of the effect of passing mirage
A layer of hot air would bend rays less
than the colder and denser air around,
and thus the stars light would not
reach the observer, rays which traversed
the hot stratum passing over his head,
and those which traversed the cold air
below being bent so as to fall beneath
his feet. As the rays of different colors
are differently bent in their passage
through the air (the red rays being the
least refracted), different parts of a
stars spectrum would be thus cut off
in succession as the relative tempera-
lures of the layers of air varied. Argos
not very lucid explanation of the inter
ference Of light, in this way is COM
pletely disposed of.
NJ. Monttigny, of Brussels, has been
investigating the amount of scintillation
in different stars by the help of an in
genious contrivance, to which he gives
the names of scintillometer. His plan
is to make use of the persistence of i'm
pressions on the retin, by causing a
thick plate of glass, mounted obliquely
on an axis, parallel to that of the tele-
scope used, and fixed Just in front of
eyepiece to rotate rapidly, the effect of
this is to displace the stars image, so
that, owing to the varying inclination
OF the glass plate, the star appears to
move in a circle, which, if the rotation
is rapid enough Cthree or four times in
a second), forms continuous circle of
light, just as in the case of a burning
stick whirled rapidly. The changes in
q color of star will be seen on this
circle, the successive points of which
give the appearance of the object at
small fractions of a second
and in this way, by counting the al
formations of color in the circumference
of this circle of light, M. Montigny has
succeeded in observing nearly two
hundred alterations of color in a
second Of time.
The point sought to be established
was the connection between these
changes and the constitution Of the
stellar light, for it is easy to see that
the rays which are deficient cannot be
acted on by undulations of the atmos-
phere, and there will therefore be fewer
changes of color the more dark bands
there are in stars spectrum. Now
Secchi has divided the stars of which
he has examined the spectra into four
types, and nj. Montigny has observed
three of these types, viz: blush white
star exhibiting four black lines in their
spectrum somewhat resembling a
As far as the results obtained
by NJ. Montigny 90, it seems that the
greatest amount of twinkling is to be
found in the first type (white stars,
and the least in the third type (orange
stars) and that the more brightness of
the star has no influence on the pheno-
mena. But the principle of combining
of different lights without
any further correction, on which NJ.
has acted, is highly objec-
and destroys our confidence In
his conclusions. The proper way of
treating such measures is to arrange
the stars in sequences representing the
order of scintillation, Just as Sir John
formed sequences of bright
ness as basis for his standard magni-
tude of stars.