Green Bank Telescope

Its 100-meter-diameter collecting area, unblocked aperture, and good surface accuracy provide superb sensitivity across the telescope's full 0.1–116 GHz operating range. The GBT is fully steerable, and 85 percent of the local celestial hemisphere is accessible. It is used for astronomy about 6500 hours out of the 8760 hours in a year, with 2000–3000 hours per year going to high-frequency science. Part of the scientific strength of the GBT is its flexibility and ease of use, allowing for rapid response to new scientific ideas and phenomena. It is scheduled dynamically to match project needs to the available weather. The GBT is also readily reconfigured with new and experimental hardware. The high-sensitivity mapping capability of the GBT makes it a vital complement to the Atacama Large Millimeter Array, the Expanded Very Large Array, the Very Long Baseline Array, and other high-angular-resolution interferometers. Facilities of the Green Bank Observatory[38] are also used for other scientific research, for many programs in education and public outreach, and for training students and teachers. The telescope began regular science operations in 2001, making it one of the newest astronomical facilities of the US National Science Foundation (NSF). It was constructed following the collapse of a previous telescope at Green Bank, the 300 Foot Radio Telescope, a 90.44 m paraboloid that began observations in October 1961.[4] This previous telescope collapsed on 15 November 1988 due to the failure of a gusset plate in the box girder assembly, which was a key component for the structural integrity of the telescope.[5]

• Built — 1990–2000

• Illustration — The Robert C. Byrd Green Bank Radio Telescope (GBT) has a collecting area of 2.3 acre which focuses the radio waves falling on it onto sensitive receivers at the top of the boom attached to the side. The telescope sits near the heart of the United States National Radio Quiet Zone, a unique area located in the town of Green Bank, West Virginia, where authorities limit all radio transmissions to avoid emissions toward the GBT and the Sugar Grove Station. The location of the telescope within the Radio Quiet Zone allows for the detection of faint radio-frequency signals which human-made signals might otherwise mask. The observatory borders National Forest land, and the Allegheny Mountains shield it from some radio interference. The telescope's location has been the site of important radio astronomy telescopes since 1957.[7] It currently houses seven additional telescopes, and in spite of its somewhat remote location, receives about 40,000 visitors each year.[8]

• Illustration — Composite image of a spectral line observation of star forming region W51, showing the distribution of ammonia in the region. The image of the telescope from a time lapse film of a night of observations In 2002, astronomers detected three new millisecond pulsars in the globular cluster Messier 62.[26] In 2006, several discoveries were announced, including a large coil-shaped magnetic field in the Orion molecular cloud,[27] and a large hydrogen gas superbubble 23,000 light years away, named the Ophiuchus Superbubble.[28][29] In 2019, the most massive neutron star PSR J0740+6620 to date was detected.[30] Since 2004, 28 new complex molecules have been discovered in the interstellar medium with the Green Bank Telescope.

In response to limited budgetary issues, the Division of Astronomical Sciences (AST) of the National Science Foundation (NSF) commissioned a portfolio review committee, which conducted its work between September 2011 and August 2012.[32][33] The committee, which reviewed all AST-supported facilities and activities, was composed of 17 external scientists and chaired by Daniel Eisenstein of Harvard University.[35] As part of the committee's August 2012 recommendation for the closure of six facilities, was that the Robert C. Byrd Green Bank Telescope (GBT) should be defunded over a five-year period.[36] In July 2014, the United States Senate Committee on Appropriations approved the NSF's fiscal year 2014 budget, which did not call for divestment of the GBT in that fiscal year. The facility then began looking for partners to help fund its $10 million annual operating costs.[37] On October 1, 2016, the National Radio Astronomy Observatory at Green Bank separated from the NSF and began accepting funding from private sources to stay operational as an independent institution, the Green Bank Observatory.

The telescope is a key facility of the Breakthrough Listen project,[39] in which it is used to scan for radio signals possibly emitted by extraterrestrial technologies. In late 2017, the telescope was used to scan the interstellar object ʻOumuamua for signs of extraterrestrial intelligence as it passed through the Solar System.[40][41]