New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1897-05-02
STUDYING STAR SPECTRA.
RECENT PHOTOGRAPHS MADE WITH
THE "PRIsMATIC CAMERA
PICTURES WHICH HELP THE ASTRONOMER To
TELL WHAT THE STARS ARE MADE
OF-sECCHrs FOUR TYPES.

PICTURES WHICH HELP THE ASTRONOMER TO
TELL WHAT THE STARS ARE MADE
oF-sEccHrs FOUR TYPES.
Few achievements OF man more wonderful
than his inquiry into the composition OF the stars
II one Of these objects were small and as easily
caught as a snowflake. and could be carried INTO
the chemists laboratory for treatment with ACIDS.
electric furnaces and microscopes. the feat would
be comparatively easy. But those tiny points OF
light are giant suns vastly larger lin some IN
stanccs) than the central luminary OF our own
solar system. and millions OF times further away
from us. Yet with the aid Of the spectroscope.
assisted by the camera. great deal Is peing
learned every year about the materials out OF
which they are made, and in regard to their tenn
perature conditions. In fact, it is along this par
ticuar line OF research that the greatest advances
are now being effected in astronomy.
Wollaston the man who first discovered mat
the rainbow -colored band into which a prism re-
solves a beam OF sunlight IL crossed by very hne.
dark lines: Fraunhofer made the first elaborate
maps of these lines. and Kirchhoff first explained
that the dark lines were due to the absorption by
yapors Of certain substances, Of light supplied by
some behind the absorbing veil. Angstrom
Thalen, Lockyer and others proceeded to identity
many Of the dark lines Of the suns spectrum with
the bright lines obtained in laboratory experiments
thus establishing the character of some OF the SUD-
atmospheres. and finally, Huggins. Secchi Nogel.
Rutherford and extended their spectroscopic
Investigations to other heavenly bodies than the
sun.
The photographs which hero reproduced. and
which were recently obtained by Professor Lockyer
at the South Kensngton Observatory, were OBJ
,aned by a method which was introduced about
ten years ago by Professor f. c. Pickering. direc'
tor OF the Harvard College Observatory. large
prism was placed just outside the object glass or A
telescope, and a Photographic plate was adjusted
In place OF the eyepiece. The image OF the star
was drawn out into a luminous streak. which was
volet-hued at one end and red at the other and
was crossed here and there by characteristic dark
lines But this streak very narrow. In order
to give It sufficient breadth TO admit OF satsfac-
tory registration, the following course was adopted
The prism so placed that the streak would be
exactly parallel with meridian OF longitude; tnat
f. II would run due north and south. Then, II tho
telescope remained stationary while the star moved
from east to west, the streak would widen out
corrcspondinsly on the sensitive plate Instead OF
leaving the instrument stationary, however 1t has
been found to be a wiser plan to let the clockwork
carry IL along but not the right rate for keep
ing the image central in the field of view. This
error of the clock is very trifng IL faint star
ia 10 be photogra phed: for in that case. the ex-
posure must be prolonged: but II be bright star
the widening process is FASTENED and shorter ex-
posure of the plate Is made.
One Of the advantages Of photography, in con-
nection with spectroscopc research. Is that the
identity of the lines can thus be more deliber-
ately Investigated than with the eye at the instru-
ment Formerly, II customary to reproduce In
| the spectroscope the spectrum OF some well-tnown
terrestrial substances. like hydrogen sodium or