CLEAR SKIES FOR NEW SUBMILLIMETER TELESCOPE AT SOUTH POLE
San Antonio, TX--A new telescope operating throughout thesix-month long Antarctic night is providing unprecedentedviews of carbon atoms in our Galaxy and ozone molecules inEarth's stratosphere. The first results from the AntarcticSubmillimeter Telescope and Remote Observatory (AST/RO) arebeing presented today at the American Astronomical Societymeeting in San Antonio, TX, by Dr. Adair P. Lane of theSmithsonian Astrophysical Observatory, Cambridge, MA. Thenew telescope, which has just completed its first year ofoperation at the U.S. National Science FoundationAmundsen-Scott South Pole Station, has also conclusivelydemonstrated that the cold, dry atmosphere over the SouthPole provides better conditions for submillimeter-waveastronomy and atmospheric studies than any other observatorysite on Earth.
Attended by winter-over scientist Dr. Richard A. Chamberlinof Boston University, the 1.7-meter diameter AST/ROtelescope spent much of the past year observing asubmillimeter-wave spectral line emitted by carbon atoms ininterstellar space. Carbon is the fourth most abundantelement in the Universe and the basis for all life on Earth. The new data suggest that atomic carbon is ubiquitous inthe Milky Way Galaxy. Emission from neutral carbon atoms isfound associated with dense, predominantly molecular, giantgas clouds, as well as with more diffuse, nearby highgalactic latitude clouds and ionized gas clouds (HIIregions). Molecular and atomic gas clouds in theinterstellar medium provide the raw material from whichstars form. Deciphering their structure, chemistry, andevolution is crucial for understanding the process of starand planet formation.
In addition, AST/RO has made the first detection of atomiccarbon in the Large Magellanic Cloud, a small companiongalaxy to the Milky Way. A large-scale survey of carbonemission from the portions of our galaxy visible from theSouth Pole is now underway. The survey is expected to takeseveral years.
"The most significant result this season comes from Dr.Chamberlin's sky measurements, which show that the SouthPole is a superb site for submillimeter astronomy," said Dr.Lane, AST/RO's Project Manager. "Much more remains to bedone in the submillimeter, and we now know that in spite oflogistical difficulties and the harsh environment, it isfeasible to do it using telescopes at the Pole. This isjust the beginning."
Submillimeter-wave radiation is readily absorbed by theatmospheric water vapor above more temperate observatorysites, so that observations are possible only from extremelydry sites (like South Pole or Mauna Kea, Hawaii), airplanes,or satellites. "When we put the telescope through tests inBoston, only one submillimeter photon in a million made itthrough the atmosphere," Dr. Lane explained. "At the SouthPole, roughly one photon in two passes through theatmosphere and is detected by our telescope."
Dr. Chamberlin was one of only 27 people who remained at theisolated base during the long winter "night" (nominally fromthe departure of the last supply aircraft on February 10 tothe arrival of the first supply aircraft on October 26). In addition to the carbon line measurements, Chamberlin usedAST/RO to measure the sky transparency at a wavelength of609 micrometers about twice a day throughout the winter. The results show that the South Pole enjoys vastly longerperiods of stable, dry observing conditions compared withother mountaintop sites.
"The best conditions at the South Pole are about twice as good as at any other site, and the average conditions are three to five times better than at other sites," said Dr. Antony A. Stark, Project Scientist for AST/RO, also of the Smithsonian Astrophysical Observatory. "This means that submillimeter-wave astronomy can be done from the South Polemost of the time, and atmospheric monitoring can be donewith regularity."
Regular monitoring of molecules in the Earth's upperatmosphere may show long term variations due to climate orman-made changes in the atmosphere. Using the AST/ROreceivers and spectrometers for only a few minutes, Dr.Chamberlin made accurate profiles of ozone and carbonmonoxide in the upper atmosphere. With AST/RO, it isparticularly easy to monitor molecules at altitudes between40 and 100 kilometers which are difficult to observe withballoons or satellites. Molecular lines can also be used tomeasure wind speed and direction in the mesosphere.
AST/RO is one of several telescopes currently operating atthe South Pole under the aegis of the Center forAstrophysical Research in Antarctica (CARA), an NSF-fundedScience and Technology Center. The highly automated AST/ROtelescope was designed and built over a five-year period byan informal consortium of astronomers from academia andindustry.
The demonstration of successful wintertime operation of a submillimeter-wave telescope at the South Pole may be a signof bigger things to come. At 1.7 meters (67 inches)diameter, AST/RO is a relatively small telescope byground-based standards, but large compared to most satellite-borne telescopes. Astronomers would like todeploy submillimeter-wave instruments 10 meters across ormore in order to study star formation regions in detail andto look at very distant galaxies. The success of the AST/ROinstrument in overcoming the logistical problems of theSouth Pole, and the demonstration of the good quality of thesky, could lead to the deployment to the Pole of futurelarge submillimeter-wave instruments.
Click here for a picture of 1995 winter-over scientist Dr. Richard A. Chamberlin next toAST/RO (Antarctic Submillimeter Telescope and RemoteObservatory), located in the "Dark Sector" at Amundsen-Scott South Pole Station. Photo credit : D. A. Harper (CARA).
For further information, contact:Dr. Adair P. Lane: Harvard-Smithsonian Center forAstrophysics
Tel: (617)496-7654, Fax: (617)496-7554
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