The Toledo chronicle. [volume] (Toledo, Tama County, Iowa) 1873-1924, 1874-07-23
Twinkling of Stars.

OF late years the SUBJECT OF the tWluk-
ling of stars has engaged good deal of
attention, and some interesting results
have been obtained A few years ago
the Italian astronomer Respighi an
nounced the discovery Of the cause of
scintillation in certain dark bands which
were seen to traverse the spectrum of
star, indicating changes in the refrangi-
bility of our atmosphere, from hot to cold
strata, which produce something of the
effect of passing mirage. A layer of
hot air would bend the rays less than the
colder and denser air around, and thus
the stars light would not reach the OBJ
server, 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
real rays being least refractedD different
parts of stars spectrum would be thus
cut off in succession, as the relative tenn
peratures of the layers of air varied
Aragos not very lucid explanation of the
phenomena, as result of the interfer-
ence of light, is in this way completely
disposed Of
NJ. Montigny, of Brussels, has been in
vestigatlng the amount of scintillation in
different stars by the help of an ingenious
contrivance, to which he gives the name
of scintillometer. His plan is to make use
~ 81, nf -.
retina by causing a thick plate of glass,
mounted obliquely on an axis parallel to
that Of the telescope used, and fixed just
in front of the eye-piece, to rotate
the stars image, so that, owing to the
varying inclination of the glass plate, the
stars appear to move in a circle, which
| (if the rotation is rapid enough, three or
| four times in second) forms continuous
circle of light, just as in the case of a
burning stick whirled rapidly The
| changes in the color of a star will be
| seen on this circle, the successive points
of which give the appearance of the OBJ
| ject at successive small fractions of a
second; and in this way, by counting the
| alterations Of color in the circumference
of this circle of light, NJ Montigny has
cecded 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 rays which are
| deficient cannot be acted on by undula-
tions of the atmosphere, and that there
will therefore be fewer changes of color
the more dark bands there are in a stars
/ spectrum. Now Secchi has divided the
stars of which he has examined the spec
ira into four types, and NJ. Montigny has
observed the scintillations Of stars be-
longing to three types, viz, blush white
stars exhibiting four black lines in their
spectrum; yellow stars, like our sun,
showing numerous fine dark lines and
orange stars, which have spectrum
somewhat resembling colonnade. AS
| far rs the results obtained by NJ Mon
| tigny go, 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
mere brightness of the star has no intlu-
ence on the phenomena But the princi
pie of combining observations of differ
ent nights without any further correc-
ton, on which NJ. Montigny has acted, is
highly Objectionable, and destroys our
confidence In ha
proper way of treating such measures is
to arrange the stars in sequences repre-
senting the order of scintillation, just as
Sir John Herschel formed sequences Of
brightness as basis for his standard
magnitudes of stars.-Chambers' Journal