Vermont watchman and State journal. [volume] (Montpelier, Vt.) 1836-1883, 1847-02-11
THE REVELATIONS OF AS
TRONOMY.
From the North British Review
COLOURED STARS.

IRONOMY.
From the North British Review.
CoLoURED STARS.
The subject of coloured stars is one of
high interest: but we have been much struck
with the fact that different observers have
ascribed different colours to the same pair of
stars. Sir w. Ilerschel, for example, makes
the two stars of Hcrcuis, blush chite and
ash cOi0ured, whereas Captain Smith makes
them ycilowiSh Uhite and orange tinted In
like manner, both Herschel and Strive have
pronounced the two stars in 7 1ndrOmadP
to be the one yeilo'o, and the other blue,
whereas Captain Smith makes them orange
and emerald green Another remarkable
coloured star is HercuiS, the larger, whose
magnitude is 3 ID, being orange, and the
other, which is 5 - i'll magnitude, being
cmerdH and blush green. Captain Smith
informs us that there are two distinct stars
near it of the 10th and 10Th magnitudes,
(which are remarkable for their lilac tinge."
The double star BOOtis, has the largest Of
the Sd magnitude, and of pale orange CO.
lour, while the next, of the 9TH magnitude,
is sra green, "the colours being distinct and
strongly contrasted," according to Captain
sohite, while that of its companion is deep
purpie, and in Serpentis, both the stars are
6Mc Mr.. Dunlop describes a large cluster
of stars in the southern hemisphere, all of
which are Jluc, and likewise nebula of a
Jluc colour; and it is mentioned by Captain
Smith as a remarkable fact, that there are
many single red stars, yet " there is not an
instance Of a solitary green, purple, 6lue, or
cioict coloured one being found" The Cir
cumstance of Sirius being called a red star
by Ptolemy and Seneca, though now it is
brightly white, has been regarded by Cap
tain Smith as affording strong presumption
that the colours of stars change, and he has
drawn similar conclusion from the fact,
that Sir w. Herschel does not mention the
colours in Leonis and Delphini, in both
of which the colours of the two stars are
distinctly visible; but little reliance can be
placed on this class of facts.
There can be no doubt that in the spec
trum of every coloured star, certain rays are
wanted which exist in the solar spectrum
but we have no reason to believe that these
defective rays are absorbed by any atmos
phere through, which they pass. We donot
know that the stars have an atmosphere, and
it is quite possible, and even probable, tha
the defective rays never existed in the ligh
of the star. In the suns light there are hun
dreds of defective rays and in the light o
Sirius, Procyon, and other stars, there arr
also defective rays, but neither the sun no.
these stars are coiOured, because the dc cctiD
rays are equally numerous an the diteren
cOloured spaces of their Spectrd, or are ST
: balanced, that their abstraction does not tax,
away from the phitcneSs of their light. w,
are not aware that any attempt has been re
Gently made to analyse the light of the col
Oured stars. The only observation witt
which we are acquainted is one made b
Sir David Brewster, about Is years ago, o
which we believe notice was read at thu
British Association A memorandum of tn
observation, of which the following is tn
substance, was inserted in Sir James South
Observatory journal, at Camden Hill, wher
il was made.
/" In the 0rdnge-coloured star ofthe dout
lie star + HercuHS, Ihave observed that Their
are several defective bands. BY applying
, fine rock salt prism, with the largest poss
BILE reiracting angle, to this orange star, a
seen in Sir James South's large achromatl
refractor its spectrum had the annexed az
pearance, clearly showing that there was on
t defective band in the red space, and two G
more in the blue space. Hence the colou
of the star was orange, because there was
greater defect of blue than of red rays
The phenomenon here described was dis
, tincty seen by the Earle of Rose (then Lor
: Oxmantown) who was one OF the party pre-
, ent in the Observatory.
5 Now, in very extensive series OF expo
riments on the combustion OF various mir
= eral and saline substances in oxygen an
= carburetted hydrogen gas, carried on by tn
' writer of this articles the coloured flame
: produced during combustion were proved, b
Q the prism, to be defective in certain band
| and lines, an effect which gave to the flame
e the colour of the predominating rays. Sine
certain coloured flames, therefore, neverpo
sessed the tints or rays in which they are d,
a fective, it is reasonable to conclude that,
g the coloured flames of the stars, the defe'
e tive rays never had an existence. If the d.
b fectve lines in the light of our sun aros
: from the absorptive agency of his atmo
: phere, then the light from the margin of ii
: SUMS disc would exhibit deeper lines tina
e those which come from his centre but Il
4 such difference exists, and hence we are Ell
i titled to conclude that these, and the
| l.. l. Il, ool., stor N,