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Slow to build, FAST to transform

Scoping out Radio Astronomy

A blog dedicated to telling the history of radio astronomy: its evolution, its discoveries, and its telescopes

Slow to build, FAST to transform

Olivia Wilkins

A new telescope achieved first light in China on September 25, 2016, perhaps bringing in a new age in radio astronomy. The Five-hundred-meter Aperature Spherical Telescope (FAST) is expected to "lead the world for at 10 to 20 years" according to Yan Jun, director general of National Astronomical Observatories of China, a division of the Chinese Academy of Sciences. A project over two decades in the making, FAST surpasses other radio telescopes in size and scope.

FAST at night (Chinese Academy of Sciences, via Sky and Telescope)

Initially proposed in 1994, FAST wasn't supported by the Chinese Academy of Sciences and the Chinese Ministry of Science and Technology until 2001 when it was named the first "Knowledge Innovation Project" of the Academy. That October, the proposal for a FAST preliminary study project was accepted, and after seven years of planning and project development (which was ultimately approved in 2007), the project finally broke ground in 2008. Another eight years of construction, and FAST finally entered the field of radio astronomy as a competitive and transformative tool.

FAST under construction (from ImagineChina)

After two decades of development, FAST emerged as the largest single-dish telescope in the world with a diameter of 500 meters (1640 feet), surpassing the previous record holder: the Arecibo telescope, which has a diameter of 305 meters (1000 feet). The large dish of FAST makes it much more sensitive than other single-dish telescopes, allowing it to detect even the faintest signals from the far reaches of other galaxies. Not only does the telescope have a uniquely high level of sensitivity as far as single-dish scopes go, but it also has a unique shape. Most telescopes have parabolic dishes, but the designers of FAST opted for a spherical design that was both cheaper and simpler to construct. Despite the benefits of construction, spherical dishes aren't as reliable when it comes to observations because they are more likely to lose focus. To overcome this, engineers designed the floor of the telescope to be made of 4,500 movable panels that can make FAST temporarily parabolic. All of these moving parts makes the telescope more complicated than other scopes, a problem that culminated in hardware issues in the months leading up to first light.

FAST upon completion (Chinese Academy of Sciences)

Hardware wasn't the only problem that arose during FAST's construction. The telescope became highly controversial when it displaced over 9,000 residents, the most recent in a string of residential uprootings by the Chinese government in favor of various types of advancement projects. The uprootings were an attempt to create a radio-quiet zone around the telescope. The quiet zone, combined with the telescope's location nestled in the mountains—a natural barrier to distant terrestrial radio waves—, will minimize interference from devices such as cell phones and WiFi that could corrupt spectral data.

Placement of FAST's last panel in July 2016 (China Daily/Reuters)

With FAST in operation and software debugging underway, the newest single-dish radio telescope could open up a new world of telescope detections. FAST is expected to probe distant galaxies for neutral hydrogen (HI) and search for faint pulsars. Among the pulsars it detects, FAST is likely to detect millisecond pulsars (with periods of 1-10 milliseconds, they rival atomic clocks as precise timekeepers) and is hypothesized to be sensitive enough to track such celestial bodies long enough to detect distortions in their periods. These distortions will provide further evidence of gravitational waves.