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CfA Press Release
 

Media Contacts
University of Arizona:
Lori Stiles, 520-626-4402,lstiles@u.arizona.edu

Harvard-Smithsonian Center for Astrophysics:
Jim Cornell, 617-495-7462, jcornell@cfa.harvard.edu

FOR RELEASE: 19 January 2000

New Detector May Open New Window on the Universe

ASTRONOMERS DETECT HIGHEST FREQUENCY RADIO EMISSIONS EVER FROM INTERSTELLAR MOLECULES

SAFFORD, Ariz.--A unique detector of astronomical radiation, developed at theHarvard-Smithsonian Center for Astrophysics (CfA), inCambridge, Mass.,and tested at the Heinrich Hertz SubmillimeterTelescope (HHT) on Mount Graham, Ariz., has made the firstground-based measurements of radio emission from interstellarmolecules in the "terahertz waveband" -- a virtually unexploredpart of the astronomical spectrum.

The unique combination of the detector, the excellent high drysite and the accurate telescope were all necessary for thismilestone in radioastronomy, astronomers say.

The detector is a superconducting hot-electron bolometer (HEB),a device analogous to the familiar AM radio receiver, butoperating at terahertz frequencies, which are about a milliontimes higher than AM radio frequencies. The key to the HEB isa detector made of a superconducting thin film of niobiumnitride, developed in a collaboration between the CfA 'sSubmillimeter Receiver Laboratory and a group at the MoscowState Pedagogical University.

The new receiver is capable of detecting and amplifyingvery-high- frequency signals with very fine frequencyresolution, so it can detect the spectral lines, or chemicalfingerprints, of interstellar molecules which emit radiosignals at terahertz frequencies -- the highest frequenciesever achieved with any radio receiver. The wavelengthscorresponding to terahertz frequencies are smaller thanone-third of a millimeter, that is, closer to infrared, aboutmidway between optical emissions and frequencies usuallyobserved by large radio telescopes such as the VLA at Socorro,N.M.

The receiver was installed on the HHT, a joint project of theSteward Observatory at the University of Arizona (UA) inTucson and the Max-Planck-Institute for Radioastronomy in Bonn,Germany. The high, dry location of the 10-meter-diameter(33-foot) telescope allows the high-frequency signals to reachthe telescope with minimum atmospheric absorption.

The HHT's reflector is a precisely figured surface -- accurateto within 12 micrometers, or about one-fifth the thickness of ahuman hair. This extreme reflector smoothness and theexcellent pointing of the HHT are essential for terahertzmeasurements. The very best observing weather is also critical.When that weather materialized the night of Jan. 7, 2000, MaxPlanck astronomers interrupted their scheduled telescopeobservations so the other astronomers could attempt theterahertz measurements.

Scientists from the CfA and UA groups collaborated in makingthe observations with the new receiver, detecting emission frommolecules of carbon monoxide (CO) in the Kleinmann-Low Nebulain the Orion Molecular Cloud. The CO emission indicates thatsome of the gas in this star-forming cloud is some ten timeshotter than average.

More important, these observations demonstrate that a"terahertz window on the universe" can be opened forground-based astronomy. Several groups are now preparinginstruments to exploit this new opportunity.

The scientists involved in the first terahertz observationsinclude Ray Blundell, Todd Hunter, Scott Paine, Cosmo Papa,and Edward Tong at the CfA; Jonathon Kawamura at Caltech; andEugene Gershenzon and Gregory Gol'tsman at the Moscow StatePedagogical University.

The Heinrich Hertz Telescope scientists involved with the firstterahertz observations include Tom Wilson, Ferdinand Patt, BillPeters, and Bob Stupak. Christian Henkel and Wilfred Walsh ofthe Max Planck Institute for Radioastronomy suspended theirregularly scheduled HHT observing time during the critical"best weather" opportunity to get terahertz signals.

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For illustrations of HHT, see:
http://maisel.as.arizona.edu:8080/

For further information, contact:
Ray Blundell, CfA, 617-495-7367, rblundell@cfa.harvard.edu

or

Tom Wilson, UA Steward Observatory, 520-621-5505, twilson@as.arizona.edu,http://maisel.as.arizona.edu:8080/heb.html

 
 
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