Southern African Large Telescope
Alternative names | Southern African Large Telescope,SALT |
---|---|
Part of | South African Astronomical Observatory |
Location(s) | Sutherland, Karoo Hoogland Local Municipality, Namakwa District Municipality, Northern Cape, RSA |
Coordinates | 32°22′34″S 20°48′38″E / 32.376005555556°S 20.810677777778°E |
Observatory code | B31 |
Altitude | 1,798 m (5,899 ft)[1] |
Wavelength | 320 nm (940 THz)–1,700 nm (180 THz) |
Built | 2005 |
Telescope style | optical telescope reflecting telescope segmented mirror |
Diameter | hexagonal array of ~11.1 m × 9.8 m 9.2 m (effective aperture) |
Angular resolution | EE(50) ≤ 0.6" |
Collecting area | 79 m2 (91 × 0.87 m2) 66.5 m2 (effective aperture) |
Mounting | 45 ton steel structure |
Enclosure | 25 m spherical |
Website | www |
Related media on Commons | |
The Southern African Large Telescope (SALT) is a 9.2-metre
SALT is the
It is closely based on the
First light with the full mirror was declared on 1 September 2005, with 1-arc-second resolution images of globular cluster 47 Tucanae, open cluster NGC 6152, spiral galaxy NGC 6744, and the Lagoon Nebula.[6] The official opening by President Thabo Mbeki took place during the inauguration ceremony on 10 November 2005.[7]
South Africa contributed about a third of the total of US$36 million that will finance SALT for its first 10 years (US$20 million for the construction of the telescope, US$6 million for instruments, and US$10 million for operations). The rest was contributed by the other partners: Germany, Poland, the United States, the United Kingdom, and New Zealand.[8]
General information
SALT is located on a hilltop 1837 m above sea level in a
Korea, Japan, Poland and Google[citation needed] have telescopes at the site and South Africa has at least five optical telescopes there. The University of Birmingham has a solar telescope to help monitor the Sun. SALT will probe quasars and enable scientists to view stars and galaxies a billion times too faint to be seen by the naked eye.
Primary mirror
Both SALT and
Each of the 91 mirrors is made of low-expansion Sitall glass and can be adjusted in tip, tilt and piston in order to properly align them so as to act as a single mirror. Because the mirror is spherical, light emitted from a position corresponding to the center of curvature of the mirror is reflected and refocused to the same position. Therefore, the telescope employs a center-of-curvature alignment sensor (CCAS) situated at the top of a tall tower adjacent to the dome. Laser light is shone down on all the segments, and the position of the reflections from each mirror measured. A process called "stacking" thus allows the telescope operator to optimize the adjustments of the mirrors.
The telescope is also unusual in that during an observation, the mirror remains at a fixed altitude and azimuth, and the image of an astronomical target produced by the telescope is tracked by the "payload", which resides at the position of prime focus and includes the SAC and prime-focus instrumentation. This is similar in operation to the Arecibo Radio Telescope. Although this results in only a limited observing window per target, it greatly simplifies the primary mirror mount, when compared to a fully steerable telescope, transferring the complexity to the smaller and lighter payload tracking system, providing for an overall reduction in total telescope construction cost. SALT has a fixed zenith angle of 37 degrees, optimised for the Magellanic clouds, but because of the full range of azimuths and the celestial rotation, SALT has access to a good fraction of the sky available at the Sutherland site.
Another consequence of this design is that the entrance pupil varies in size during the tracking of a target.
Instrumentation
The first generation instrumentation for SALT includes the SALT Imaging Camera (SALTICAM), designed and built by the South African Astronomical Observatory (SAAO); the Robert Stobie Spectrograph (RSS) (née Prime Focus Imaging Spectrograph), a multi-purpose long-slit and multi-object imaging spectrograph and spectropolarimeter, designed and built by the
Internet connectivity
The telescope is connected to the
Science working group
Membership of the SALT science working group:
David Buckley, Gerald Cecil, Brian Chaboyer, Richard Griffiths, Janusz Kałużny, Michael Albrow, Karen Pollard, Kenneth Nordsieck, Darragh O'Donoghue, Larry Ramsey, Anne Sansom, Pat Cote.
Partners
- Dartmouth College
- Georg-August-UniversitätGöttingen
- Hobby-Eberly TelescopeBoard
- National Research Foundation of South Africa
- Nicolaus Copernicus Astronomical Centre of the Polish Academy of Sciences
- Rutgers, the State University of New Jersey
- University of Wisconsin–Madison
- University of Canterbury (New Zealand)
- University of North Carolina at Chapel Hill
- United Kingdom SALT Consortium (UKSC), comprising:
In 2007, the following new partners joined the SALT consortium:
- American Museum of Natural History
- Inter-University Centre for Astronomy and Astrophysics(India)
Research
Research using SALT at the South African Astronomical Observatory has led the facility to important discoveries. By using the Southern African Large Telescope, SAAO has the ability to take "snapshots" of stars in very quick succession. It is optimized for wavelengths and observing modes not available on other very large telescopes. As a result, astronomers can study rapidly changing properties of compact stars, primarily as they pull in gas from their companion stars or surroundings. The significance of this discovery allows us to detect black holes. The gravitational field of a compact star commonly pulls in gas from a companion star, thus radiation (especially X-ray) is emitted. Scientists used this as an indirect way to locate black holes. Another phenomenon that SALT has helped astronomers investigate is the way that masses build up on some compact stars until supernova explosions blow them apart, which gives scientists a "Type 1a" supernovae used to show that the expansion of the universe is speeding up.[9]
Other note-worthy research the South African Astronomical Observatory has achieved using SALT include the discovery of a class of stars known as "polar", or a pair of stars. The "polar" binary star system, where a compactor star called a "white dwarf" whose volume has shrunk about one millionth of a star like the Sun. Studies using SALT concluded that these polar binary star systems take only an hour and a half to complete an orbit. Also, the SALT telescope allows scientists to study the rapid brightness changes in exotic stars.
More research using SALT has aided astronomers to investigate the structure and evolution of our
Tourism
Despite initial estimates by SAAO that SALT would bring up to 30,000 tourists to Sutherland, the telescope has so far only resulted in about 14,000 annual visitors, which has nevertheless resulted in the creation of at least 300 jobs in the town of 5,000.[8]
See also
- South African Astronomical Observatory
- List of astronomical observatories
- SEDSSEDS South Africa
- List of optical telescopes
- List of largest optical reflecting telescopes
References
- Reuters. South Africa looks to stars with super scope. United Kingdom: Reuters Limited. 15 March 2004.
- South African Large Telescope Makes Its Debut. PhysOrg.com. 1 September 2005
Notes
- ^ [2013 "SALT Key Design & Performance Characteristics"].
Operational wavelengths: 320nm to 1700nm
{{cite web}}
: Check|url=
value (help) - ^ "Mirror Segments". Southern African Large Telescope website. SOAA. Retrieved 10 May 2013.
The spherical primary mirror has a master radius of curvature of 26 165 mm. It consists of 91 interchangeable hexagonal mirror segments, each of 1 m inscribed diameter, forming a hexagon of ~11.1 x ~9.8 m.
- ^ "Deep Space Observatories: The Southern African Large Telescope". Space Today Online. Retrieved 28 January 2009.
- ^ "273 Precision Actuators for the Largest Telescope in the Southern Hemisphere". Physik Instrumente (PI) GmbH & Co. KG. May 2003. Retrieved 28 January 2009.
- ^ "Southern African Large Telescope". Armagh Observatory. Archived from the original on 6 April 2012. Retrieved 28 January 2009.
- ^ "S.a.l.t". May 2008.
- South African Department of Science and Technology. 10 November 2005. Archived from the originalon 25 September 2008. Retrieved 30 January 2009.
- ^ a b Kahn, Tamar (1 June 2018). "Sutherland: Wishing on a rising star".
- ^ "First Science with SALT: Observations of eclipsing polar: SAAO". Archived from the original on 25 December 2012. Retrieved 30 January 2009.
- ^ "NRF - the South African Astronomical Observatory". Archived from the original on 24 December 2008. Retrieved 30 January 2009.
External links
- Official website
- Near Earth Object Observations by SALT
- SALT Camera[permanent dead link] – Live view of SALT.