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Green Bank Telescope
GBT.png
Organization NRAO
Location Green Bank, West Virginia, USA
Coordinates 38°25′58.23″N 79°50′21.88″W / 38.4328417°N 79.8394111°W / 38.4328417; -79.8394111Coordinates: 38°25′58.23″N 79°50′21.88″W / 38.4328417°N 79.8394111°W / 38.4328417; -79.8394111
Wavelength radio telescope and microwave band
Built 1991-2002
First light August 22, 2000
Telescope style Parabolic off-axis reflector, Gregorian optics
Diameter 100m
Collecting area 7,854m2
Focal length 60 m
Mounting wheel and track mount
Website www.gb.nrao.edu/GBT/GBT.shtml

The Robert C. Byrd Green Bank Telescope (GBT) is the world's largest fully steerable radio telescope and the world's largest land-based movable structure. It is part of the National Radio Astronomy Observatory (NRAO) site at Green Bank, West Virginia (USA). The telescope honors the name of Senator Robert C. Byrd.

The current telescope was built following the collapse of the previous Green Bank telescope, a 300ft paraboloid. The previous telescope collapsed on 15 November 1988 due to the sudden loss of a gusset plate in the box girder assembly, which was a key component for the structural integrity of the telescope.[1]

Contents

Location

The telescope sits at the heart of the United States National Radio Quiet Zone, a large area where all radio transmissions are either limited or banned outright, to help the telescope function properly.

Description

The surface area of the GBT is a 100 by 110 meter active surface with 2,209 actuators (a small motor used to adjust the position) for the 2,004 surface panels. The panels are made from aluminium to a surface accuracy of better than 0.003 inches (76.2 micrometers) RMS. The actuators adjust the panel positions to correct for distortions due to gravity which change as the telescope moves. Without this so-called "active surface", observations at frequencies above 4 GHz would not be as efficient.[2]

The telescope is unusual in that the mirror is not a symmetrical dish, but is a section of a much larger parabolic figure with the receiver where the prime focus of the entire mirror would be. As a result, the support for the receiver does not in any way obscure the mirror's view of the sky.

The offset support "arm" houses a retractable prime focus feed horn in front of the 8 m subreflector and eight higher-frequency feeds on a rotating turret at the Gregorian focus. Operational frequencies range from 290 MHz to 90 GHz.

Discoveries

In 2002, astronomers detected three new millisecond pulsars in the globular cluster Messier 62. [3]

In 2006, several discoveries were announced, including a large coil-shaped magnetic field in the Orion molecular cloud, [4] and a large hydrogen gas superbubble 23,000 light years away, named the Ophiuchus Superbubble.[5][6]

See also

References

External links

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