The technology of
radio telescopes begins with the work of Karl
Jansky who
detected the first radio emissions from the center of our galaxy,
and continues to Grote Reber who built
and perfected the first radio telescope
which he used to map the low energy radiations from many sectors of the
milky
way galaxy.  Karl Oort and
and H.C. Van
Hulst added theoretical physics to the developing technology with their
predictions of the 21 cm transition of the hydrogen atom. The
predicted radiation was detected by Ewen
and Purcell in 1951. Although many
molecules had been detected by absorption spectroscopy the combination
of theoretical physics and the new technology marked the
beginnings of astrochemisry. In 1963
low energy transitions of the hydroxyl radical
were detected in the
dense gas
surrounding Cassiopeia
A.
Subsequent to
the discovery of the OH radical, radio astronomers detected NH3,
H2O
, and H2CO at 1.2 and 6 cm in 1968.
In 1970 astrochemists using the NRAO radio telescope observed
large
amounts of CO from the Orion Nebula at 3mm. ( See Chronology of
Radio Telescopes for detailed history of the technology of radio
telescopes). As a result of the improvements in sensitivity and
range, contemporary telescopses are described by the area of the
EMS in which they collect emissions. Thus there are millimeter, sub
millimeter, and centimeter telescopes. In addition to large
single dish telescopes, such as the
100 m Green
Bank Telescope and the 12
meter NRAO ( National Radio Astronomy
Observatory) Telescope, groups of
radio telescopes can be connected and synchronized so that they
collect data as one large instrument. These
interferometer arrays such as the BIMA
and Allen
Telescope Array are used to gather data from very distant
stellar objects. The
NRAO telescope has been instrumental in the discovery of interstellar
compounds. It is the instrument used by Hollis et al to detect
glycolaldehyde.
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