The James Clerk Maxwell Telescope
The James Clerk Maxwell Telescope (JCMT) is one of two
by the Joint Astronomy Centre, the other being the United
Kingdom Infrared Telescope (UKIRT).
The JCMT on Mauna Kea.
The JCMT is the largest single-dish telescope in the world
to detecting submillimetre radiation. Its 15-metre (50-foot)
dish looks at the sky with instruments that tell us about the
cold Universe in different ways. Operating between the infrared
and radio waves, it uses some of the most sensitive and
sophisticated instrumentation to detect the coldest material in
the Universe, only a few tens of degrees above absolute zero.
Water vapour in the Earth’s atmosphere intercepts this
radiation, making the high and dry site of Mauna Kea vitally
important for the research performed at the JCMT.
The JCMT looks upward and outward.
The JCMT's dish, as wide as a basketball court, collects the
light and feeds it to a set of sensitive detectors. The dish is
wind, sand and birds by a sailcloth-like membrane or Gore-Tex.
The JCMT's dish.
In between the stars are giant clouds where stars and solar
systems are born. They are made of gas (mostly
hydrogen) and cosmic dust (tiny particles of silicate
and carbon). The clouds are some of the coldest objects in the
Universe - so cold that their "heat glow" is invisible to human
eyes. We need specialised telescopes
and instruments to see this submillimetre radiation.
SCUBA-2 arrives at the JCMT (April 2008).
The newest instrument on the JCMT is SCUBA-2 which is the
most powerful camera of its kind. New technology and novel
design means it can map the sky faster than its predecessor,
SCUBA. SCUBA-2 has 5120 pixels (4 sub arrays x 1280 pixels) at
two wavelengths. Sensitivity requirements mean that these
detectors within SCUBA-2 are cooled to temperatures just less
than 0.1K = -272.9°C = -459.2°F
SCUBA-2 begins science operation (late
The SCUBA-2 instrument is keeping the JCMT at the forefront
of submillimetre astronomy, complementing the Submillimeter
Array on Mauna Kea and forthcoming telescopes such as the
Atacama Large Millimeter Array in Chile.
The JCMT also has 'heterodyne receivers' which detect light
from gas molecules
in space. These molecules emit characteristic submillimetre
when they rotate. The patterns are 'fingerprints' that tell
us about the
temperature, density, or motion of the gas. HARP is such an
instrument which combines a camera and a spectrometer. This
means we can learn about the chemistry of interstellar gas,
its temperature, density and motion.
HARP on JCMT.
The nearest massive star formation to Earth is happening
1500 light years
away in the constellation of Orion, the Hunter. In this
cloud new stars are born, and into this stars disperse or
explode as they die. HARP's images of Orion show the
presence of carbon monoxide. The bright region in the center
new star formation. Evident is the surrounding gas
streaming motions both to and away from the region.
The JCMT is internationally funded by the UK and Canada. It
was opened in April 1987.
You can find some more technical information in a
previous article about the JCMT.