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among astronomers will be the results
that are expected of Palomar in carrying
farther among the extragalactic nebulae
the work that has been done with the
IOO-inch mirror. Dr. Hubble, who has
widened knowledge of this realm through
use of the Mount Wilson telescope, feels
confident that the greater depth of pene-
tration will settle the question as to
whether or not the red shift of nebular
spectral lines is a true Doppler effect.
This apparent outward motion of dis-
tant galaxies is the observational founda-
tion upon which is based the thcory of an
expanding universe. Assume the appar-
ent recession continued unchanged to
distances twice those that have been spec-
troscopically examined with present
equipment. Then, the velocities of the
nebulae, if they are real as well as ap-
parent, would be so large a fraction of
the velocity of light that the brightnesses
would be reduced measurably, Hubble
estimates by 40 or 50 per cent. Fewer
photons are received from a receding
light source in proportion as its velocity
is a fraction of the velocity of light. If
the nebulae are not dimmed by this cause,
the red shift can no longer be used as an
argument for an expanding universe, and
some other explanation for this effect
will have to be sought. Other causes
have already been suggested, or perhaps
we should say imagined, for the Doppler
effect is the only one with experimental
evidence.
Another outstanding advantage of the
Palomar telescope's power to collect light
will be evident when it is used in spectro-
scopic work on dim stars. If a star is so
faint that its entire light must be focused
A cutaway drawing by Russell W. Porter of the vacuum chamber for aluminizing
at a point to make it visible, it is obvi-
the 200-inch mirror. The entire tank is divided horizontally into three sections,
ously useless to try to spread this light
one below the mirror and containing the cell, the second around the mirror's
out into a set of lines that will reveal
periphery, and the topmost portion containing the heating elements and the mir-
the nature of the star. With a four-fold
ror's surface. The operator is shown working a manual control to fire separately
each of the individual tungsten filament units that carry the small aluminum
accession of light, a four-fold lengthening
horseshoes, which are so distributed over the ceiling of the bell jar that the
of the spectra of dwarf stars and of
coating on the mirror is of an even thickness. Caltech photograph.
stars dimmed by distance will give the
astronomer a double range in which to
fraction disks, and thereby have been able
smears out such details as the so-called
employ his spectrograph, and therefore
to run up useful magnifying power and
canals, which have been seen visually by
eight times as many such stars of which
ability to resolve images, first by using
many observers.
he can get readable spectra. Already,
the shorter-wave ultraviolet light. This
Edison Pettit, of the Mount Wilson
spectra of extragalactic nebulae have been
increased magnifying power is possible
Observatory, who has published sketches
made out to distances of nearly half of
from about 1,000 diameters to 2,000.
from his visual observation of Mars, esti-
the 500 million light-years to which
Then, with the electron microscope, they
mates that, with the increased light the
dimmer ones can be photographed. Such
have been able to increase to more than
large telescope will give, photographs
spectrographic study of other galaxies
50,000 the magnification of their well-
through a yellow filter can be made in
will be extended with the Palomar tele-
resolved images so as to see organisms
1/60 of a second. Dr. Hubble, who is
scope just as it is to be extended among
not visible with light. But they do not
chairman of the Palomar research com-
the stars of our own galaxy.
have several hundred miles of atmosphere
mittee, believes that by taking many pic-
Will the new telescope simply add
to contend with, as astronomers have.
tures on movie film some of them may
quantity to the known universe, or will
Nevertheless, one of the accomplish-
happen to be made "at the end of a
it add, also, quality Will it help to
ments hoped for from the Palomar tele-
flicker of the image - when it is mo-
tell what kind of a universe we live in ?
scope will be an occasional instantaneous
mentarily at rest as it reverses its direc-
One astronomical question on the qual-
photograph of Mars. The light of Mars
tion" and that a small percentage of them
ity of the universe is: How much of each
is strong, but it is reduced by the neces-
may show what the eye can see. One
element is found in the make-up of stars
sity of employing a yellow or red filter
such picture might make a photographic
There is some indication that as many
in order to make use of the wave lengths
finish of the perennial argument as to the
as 99 per cent of the atoms of the uni-
that can best penetrate its own atmos-
reality of the criss-cross markings on
verse are hydrogen atoms. At least a
phere. Thus, time exposures have always
Mars.
third, by weight, of the material in the
been necessary and atmospheric tremor
Of perhaps more general interest
sun seems to be hydrogen. But the sun
62 SKY AND TELESCOPE, January, 1948
Document source description
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"ocrText": "among astronomers will be the results\nthat are expected of Palomar in carrying\nfarther among the extragalactic nebulae\nthe work that has been done with the\nIOO-inch mirror. Dr. Hubble, who has\nwidened knowledge of this realm through\nuse of the Mount Wilson telescope, feels\nconfident that the greater depth of pene-\ntration will settle the question as to\nwhether or not the red shift of nebular\nspectral lines is a true Doppler effect.\nThis apparent outward motion of dis-\ntant galaxies is the observational founda-\ntion upon which is based the thcory of an\nexpanding universe. Assume the appar-\nent recession continued unchanged to\ndistances twice those that have been spec-\ntroscopically examined with present\nequipment. Then, the velocities of the\nnebulae, if they are real as well as ap-\nparent, would be so large a fraction of\nthe velocity of light that the brightnesses\nwould be reduced measurably, Hubble\nestimates by 40 or 50 per cent. Fewer\nphotons are received from a receding\nlight source in proportion as its velocity\nis a fraction of the velocity of light. If\nthe nebulae are not dimmed by this cause,\nthe red shift can no longer be used as an\nargument for an expanding universe, and\nsome other explanation for this effect\nwill have to be sought. Other causes\nhave already been suggested, or perhaps\nwe should say imagined, for the Doppler\neffect is the only one with experimental\nevidence.\nAnother outstanding advantage of the\nPalomar telescope's power to collect light\nwill be evident when it is used in spectro-\nscopic work on dim stars. If a star is so\nfaint that its entire light must be focused\nA cutaway drawing by Russell W. Porter of the vacuum chamber for aluminizing\nat a point to make it visible, it is obvi-\nthe 200-inch mirror. The entire tank is divided horizontally into three sections,\nously useless to try to spread this light\none below the mirror and containing the cell, the second around the mirror's\nout into a set of lines that will reveal\nperiphery, and the topmost portion containing the heating elements and the mir-\nthe nature of the star. With a four-fold\nror's surface. The operator is shown working a manual control to fire separately\neach of the individual tungsten filament units that carry the small aluminum\naccession of light, a four-fold lengthening\nhorseshoes, which are so distributed over the ceiling of the bell jar that the\nof the spectra of dwarf stars and of\ncoating on the mirror is of an even thickness. Caltech photograph.\nstars dimmed by distance will give the\nastronomer a double range in which to\nfraction disks, and thereby have been able\nsmears out such details as the so-called\nemploy his spectrograph, and therefore\nto run up useful magnifying power and\ncanals, which have been seen visually by\neight times as many such stars of which\nability to resolve images, first by using\nmany observers.\nhe can get readable spectra. Already,\nthe shorter-wave ultraviolet light. This\nEdison Pettit, of the Mount Wilson\nspectra of extragalactic nebulae have been\nincreased magnifying power is possible\nObservatory, who has published sketches\nmade out to distances of nearly half of\nfrom about 1,000 diameters to 2,000.\nfrom his visual observation of Mars, esti-\nthe 500 million light-years to which\nThen, with the electron microscope, they\nmates that, with the increased light the\ndimmer ones can be photographed. Such\nhave been able to increase to more than\nlarge telescope will give, photographs\nspectrographic study of other galaxies\n50,000 the magnification of their well-\nthrough a yellow filter can be made in\nwill be extended with the Palomar tele-\nresolved images so as to see organisms\n1/60 of a second. Dr. Hubble, who is\nscope just as it is to be extended among\nnot visible with light. But they do not\nchairman of the Palomar research com-\nthe stars of our own galaxy.\nhave several hundred miles of atmosphere\nmittee, believes that by taking many pic-\nWill the new telescope simply add\nto contend with, as astronomers have.\ntures on movie film some of them may\nquantity to the known universe, or will\nNevertheless, one of the accomplish-\nhappen to be made \"at the end of a\nit add, also, quality Will it help to\nments hoped for from the Palomar tele-\nflicker of the image - when it is mo-\ntell what kind of a universe we live in ?\nscope will be an occasional instantaneous\nmentarily at rest as it reverses its direc-\nOne astronomical question on the qual-\nphotograph of Mars. The light of Mars\ntion\" and that a small percentage of them\nity of the universe is: How much of each\nis strong, but it is reduced by the neces-\nmay show what the eye can see. One\nelement is found in the make-up of stars\nsity of employing a yellow or red filter\nsuch picture might make a photographic\nThere is some indication that as many\nin order to make use of the wave lengths\nfinish of the perennial argument as to the\nas 99 per cent of the atoms of the uni-\nthat can best penetrate its own atmos-\nreality of the criss-cross markings on\nverse are hydrogen atoms. At least a\nphere. Thus, time exposures have always\nMars.\nthird, by weight, of the material in the\nbeen necessary and atmospheric tremor\nOf perhaps more general interest\nsun seems to be hydrogen. But the sun\n62 SKY AND TELESCOPE, January, 1948"
}