CALTECH

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CALTECH SUBMILLIMETER
OBSERVATORY
The 10.4 meter (33ft) reflector dish is snuggly
housed within a hemispherical dome. As the dish
is rotated to various parts of the sky, the dome
must turn with it.
CSO observes in the region between the infra-red
and microwaves.
The radiation reflected by the dish converges
towards the apex of the spider sitting on the
dish, where a second mirror directs the radiation
back towards the dish and passes thru a hole in
the center. Behind this hole are located the
various detectors that can analyze the radiation.
This image of the Horsehead nebula in Orion is a
good example of how the CSO telescope can observe
structure in a cloud of dust and gas. The green
and yellow areas are regions of greater
concentration of carbon monoxide, suggesting
potential future sites of star formation.
In the constellation ORION is found the great
Nebula M42 seen to the right above in visible
light. M42 is about 25 light years (LY) across
and 1300 LY away. Light from stars hidden by
the cloud
In visible light, this same feature appears as a
dark cloud, where dust and dense gas obscure any
internal structure. The stars seen here are all
in front of the dark cloud. The CSO image above
is made up of many little colored squares because
the resolution of the telescope does not approach
that of telescopes in visible light.
is reflected and scattered by the dust and
molecules of the cloud, but the brightest regions
are molecular emissions stimulated by ultraviolet
from the stars. Below, to the right, is an image
of the same region, at the submillimeter
wave-length of 0.35 mm. This is the radiation
actually emitted by the cold, dense cloud of gas
and dust and is many orders of magnitude fainter
than the scattered visible light.
Here is another view of the Orion Molecular
Cloud. This image was made at a wavelength of
3.8 cm, the microwave region of the spectrum. As
in the submillimeter image, no stars are visible,
only the radiation emitted by the gas and dust in
the cloud.
Image courtesy of Darek Lis.
Only in the millimeter and submillimeter region
would this radiation be observable, as shown by
the graph below of relative power versus
wavelength of a body at a temperature of 20
degrees above absolute zero.
The bright main region is called the Orion
Molecular Cloud (OMC-1), rich in dozens of
molecular species. The diagonal bar seen in the
lower part of the upper view is clearly visible
as a bright green region in the lower view.
In this infrared view of the Orion Nebula taken
at the new Subaru telescope, we are able to see
through the clouds of gas and dust to the many
stars obscured in visible light. The four bright
stars in the center, known as the Trapezium, are
the source of the ultraviolet that radiates the
dust and gas and stimulates its glowing.
These four views of the Orion Molecular Cloud
appear quite different from each other, but note
the diagonal bar in the lower portion of each.
These bright regions represent sites of active
star formation, where ultraviolet radiation from
the young stars shines on the thick cocoon of
dust and dense gas from which the stars are born

In the above submillimeter view the receiver is
tuned to one frequency as the object is mapped
out. But the telescope can also look at one part
of the sky and scan the entire frequency range of
the receiver, thus showing all the emissions or
radio stations broadcasting within that range.
This is called a frequency spectrum, and one such
is seen on the left. The region being observed is
in the OMC-1 discussed above.
ABOUT CSO _ _ _ Funded by the National
Science Foundation, the Caltech Submillimeter
Observatory (CSO) is operated by the California
Institute of Technology. The primary reflector is
a 10.4 meter (34 ft) dish located on the summit
of Mauna Kea. Commissioned in 1987, the
telescope remains the world's premier
sub-millimeter telescope operating in the
frequency range of 180--850 GHz (1.7 to 0.35
mm in wave- length).
Orion KL line survey, 607-725 GHz (Schilke
et al. 2000)
Some of the stations come in loud and clear,
while others are quite faint. But each station
represents a particular molecular species or
sub-species. The stronger the signal, the more
abundant that particular molecule must be. Many
of the peaks in this spectrum have been
identified and are seen to be compounds of
carbon. So, are they organic compounds?
Steiger_at_hawaii.edu
The Caltech Submillimeter Observatory base
facility is located in the University of Hawaii
at Hilo Research Park 111 Nowelo Street, Hilo,
Hawaii 96720. Telephone [phone], Fax
808-961-6273. Please visit our web site at
http//www.submm.caltech.edu
.