The Primeval Structure Telescope (PaST), also called 21 Centimetre Array (21CMA),
is a Chinese radio telescope array designed to detect the earliest luminous objects in the universe, including the first stars, supernova explosions, and black holes, in the range of 100 to 1 billion years ago.
All of these objects were strong sources of
ultraviolet
Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of ...
radiation, so they ionised the material surrounding them. The structure of this
reionisation reflects the overall density structure at the redshift of luminous-object formation.
Location
The telescope is built on the high plateau of
Ulasitai () in
Xinjiang
Xinjiang,; , SASM/GNC romanization, SASM/GNC: Chinese postal romanization, previously romanized as Sinkiang, officially the Xinjiang Uygur Autonomous Region (XUAR), is an Autonomous regions of China, autonomous region of the China, People' ...
, close to the southern entrance of the
Tianshan Shengli tunnel. This is a remote area away from most television and radios signals that may interfere the weak
21 cm background signals. It is also close to the existing Urumqi
VLBI
Very-long-baseline interferometry (VLBI) is a type of astronomical interferometry used in radio astronomy. In VLBI a signal from an astronomical radio source, such as a quasar, is collected at multiple radio telescopes on Earth or in space. T ...
station (Nanshan Observatory) in
Gangou township.
Overview
PaST consists of an array of some ten-thousand log-periodic antennas spread over several square kilometers. It will capture a detailed radio image of the sky in the range of 1420 MHz.
The first stars ionized the gas around them, which produced a specific pattern of ionization. PasT detects the brightness of the 21 cm
hydrogen line
The hydrogen line, 21 centimeter line, or H I line is a spectral line that is created by a change in the energy state of solitary, electrically neutral hydrogen atoms. It is produced by a spin-flip transition, which means the dire ...
at redshift from 6 to 25. This hydrogen cosmic background radiation disappears on ionization, allowing the study of large scale structure and of star formation at this very early epoch.
Hardware
PaST's detection antennas are located over an area measuring several km². The redshift of 6 to 25 corresponds to a frequency range of 200 MHz to 50 MHz. Despite the remote location, some man-made frequency lines are to be filtered out.
At 100 MHz, the telescope covers an area of the sky of 3 arcminutes.
For detection, PaST's antennas use 20 off-the-shelf
interferometers and a total of 10,000 antennae.
See also
*
List of radio telescopes
This is a list of radio telescopes – over one hundred – that are or have been used for radio astronomy. The list includes both single dishes and interferometric arrays. The list is sorted by region, then by name; unnamed telescopes are in ...
*
Five-hundred-meter Aperture Spherical Telescope
References
*
* Pen, U. L.; Wu, X. P.; Peterson, J. B., 2004,
Forecast for Epoch-of-Reionization as Viewable by the PrimevAl Structure Telescope (PAST), ''Chinese Journal of Astronomy and Astrophysics''.
External links
*
{{Portal bar, China, Astronomy, Stars, Outer space, Education, Science
Radio telescopes
Buildings and structures in Xinjiang
Chinese telescopes
Interferometric telescopes