CfA 1.2 m Millimeter-Wave Telescope

In the early 1970s, an astronomer at the Goddard Institute of Space Studies in New York named Patrick Thaddeus shattered centuries of precedent in the field of astronomy and bucked a trend dating all the way back to Galileo when he decided that, in order to proceed on a modest project to map the entire Milky Way, he simply did not need and in fact refused to use a larger telescope made available for his research. He wanted a small one. In an era made conspicuous by bigger, more sophisticated, and (need it be added?) more expensive telescopes, Thaddeus insisted on a small and relatively inexpensive instrument, which he and his colleagues proceeded to build from scratch.

Stephen S. Hall, Mapping the Next Millennium

The 1.2 meter Millimeter-Wave Telescope at the Harvard-Smithsonian Center for Astrophysics and its twin instrument at CTIO in Chile have been studying the distribution and properties of molecular clouds in our Galaxy and its nearest neighbours since the 1970s. The telescope is nicknamed "The Mini" because of its unusually small size. At the time it was built, it was the smallest radio telescope in the world. Together, "The Mini" and its twin in Chile have obtained what is by far the most extensive, uniform, and widely used Galactic survey of interstellar carbon monoxide (CO). "The Mini" is currently in operation from October to May each year.

Interstellar CO is the best general tracer of the largely invisible molecular hydrogen that constitutes most of the mass in molecular clouds. Hydrogen is the simplest and most abundant element in the universe, and molecular hydrogen (H2) is by far the most abundant molecule. Unfortunately, under typical interstellar conditions H2 does not emit at radio or millimeter wavelengths.

CO, however, the second most abundant ingredient in molecular clouds, has a rich and strong millimeter-wave spectrum and it seems to maintain a fairly constant ratio with H2 of about 1:100,000. For this reason, CO has become the standard tracer or "stain" for the invisible H2 which constitutes most of the molecular mass.

A total of 24 PhD dissertations have so far been written based on observations or instrumental work with these telescopes.

The 1.2 meter telescope has played an important or dominant role in all of the important general findings on molecular clouds (MCs) listed below. Many of these are now considered conventional wisdom but some were originally controversial (e.g., the very existence of giant molecular clouds, their ages, and their confinement to spiral arms).

Prof. Patrick Thaddeus (the Robert Wheeler Willson Professor of Applied Astronomy, Emeritus, Harvard University; Senior Space Scientist, Smithsonian Astrophysical Observatory), continues to lead the Millimeter-Wave group. Tom Dame (Radio Astronomer, Smithsonian Astrophysical Observatory; Lecturer on Astronomy, Harvard University) has coordinated telescope observations over the last decade. Sam Palmer (Electronics Engineer, Smithsonian Astrophysical Observatory; Lecturer on Astronomy, Harvard University) continues to maintain the telescope hardware.

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