CALTECH SUBMILLIMETER OBSERVATORY

1. 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 isanother 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 shownby 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 ScienceFoundation, 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@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: 808-935-1909, Fax: 808-961-6273. Please visit our web site at : http://www.submm.caltech.edu .