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| September 2005 |
Feature |
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'First-Light' for Africa’s Giant Eye
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This image of the globular star cluster known as 47 Tucanae was obtained by combining images taken through three different filters with total exposure times of 120 sec (U filter), 20 sec (V filter) and 20 sec (I filter). 47 Tucanae is an ancient cluster of several million stars (as many as in some very small galaxies), about 15,000 light years from Earth, and 120 light years across. |
Exactly five years after groundbreaking, the Southern African Large Telescope (SALT) project has released its first colour images, marking the achievement of 'first light' and the successful debut of full operation for SALTICAM, a $600 000 digital camera designed and built for SALT at the South African Astronomical Observatory (SAAO). SALT is the largest optical telescope in the southern hemisphere, and equal to the largest in the world.
Gathering more than 25 times as much light as any existing African telescope,
SALT can detect objects as faint as a candle flame on the moon. The sample
images now released for the first time were taken
during the camera's first trial period of operation, which also achieved SALT's
first significant scientific results.
The images shown here are a first indication of SALT's capabilities. While the imaging quality is not yet at its final optimal value, the sheer light gathering power of the telescope is amply demonstrated in these images. Most of the colour images were produced by combining separate images in three filters: ultraviolet (U), visible (V) and infrared (I), each with an exposure time typically of 10 – 120 seconds. The galaxy image (NGC6744) was made by combining ultraviolet, blue and infrared images. Eventually the sharpness of SALT's images will be improved by the full implementation of its active optics control, but this is not operational yet.
The project has seen many highlights this year, with the last of the 91 hexagonal mirror segments that comprises SALT's mammoth primary mirror array, stretching 11 metres across installed n May this year. Attaining "first light" with the telescope's full array of mirrors and its new imaging camera, SALTICAM is one big step towards the completion of SALT with its official opening planned for 10 November this year.
NGC 6152 is a small 'open cluster', a group of stars which all formed at about the same time perhaps a billion years ago. These few dozen stars formed close enough to each other that gravity has kept them travelling together around the centre of our galaxy since they were born. In this image the stars appear relatively sharp across the picture, because the 91 mirrors in SALT's primary mirror array are aligned fairly close to optimum. This is the only image which shows what a normal SALTICAM image looks like. |
Limited scientific observations have already begun with SALT while completion of the telescope's commissioning continues over the coming months. In the next month or so, installation will begin of the major first generation instrument, the Prime Focus Imaging Spectrograph (designed and built for SALT by the University of Wisconsin-Madison and Rutgers University) – which is to be renamed the Robert Stobie Spectrograph in honour of the past SAAO Director and Chairperson of the SALT Board, Dr Robert S. Stobie.
The declaration of first light signifies that SALT has arrived on the astronomical scene. There is still telescope and instrument commissioning to complete, as well as full optimisation of SALT and its subsystems. This will continue for several months, after which astronomers confidently expect that SALT and its instruments will meet or exceed all the original design goals. This process is already well under way with much achieved, and SALT is now in a very real sense an operational telescope.
Astronomers within the SALT consortium keenly look forward to the scientific fruits of what has been, until now, an extremely successful engineering project. Already proposals for observations have been submitted and approved, and these observations are now beginning with the imaging camera, SALTICAM. The same will be true for the Robert Stobie Spectrograph, once it completes its commissioning tests in October. Like the SALT consortium itself, the science programmes to be conducted on SALT will be many and varied – from studies of the most distant and faint galaxies to observations of solar system objects like asteroids and comets.
SALT is truly representative of the century in which it has been built, since not only is it a sophisticated computer controlled precision instrument, but it is also an Internet-age telescope. No longer will it be necessary for astronomers in the consortium to travel to SALT to use it. Instead they will submit their observing requests over the Internet and eventually, once the observations have been conducted by the dedicated SALT operations staff, they will also receive their data over the Internet. In many respects this makes SALT far more like a space-based telescope, like the Hubble Space Telescope, than its ground based cousins. The operational model for SALT, with SAAO operating the telescope on behalf of SALT's partners, will also be far closer to the way a telescope in orbit operates.
But the scientific and engineering achievements of the SALT project would have fallen short of the vision that led the South African government (with standing applause from every political party) to approve SALT, unless it did more than provide a spectacular tool for southern African and overseas scientists to explore the universe and extend human knowledge.
NGC 6744 is a large face-on barred spiral galaxy in the star-rich southern constellation of Pavo. It lies at a distance of approximately 30 million light years, and is almost 150 000 light years across. Its overall appearance, shape and size are very much like our own Milky Way galaxy. |
Already the benefits have been tangible, with the provision of bursaries and scholarships to deserving South African students to study both in South Africa and abroad. These programmes have been directly sponsored by many of the partners in the SALT Foundation. A number of science education initiatives have also been catalysed by the project, and many more are foreseen. Financially South Africa has benefited by the awarding of ~60% of the contracts and tenders to construct SALT to South African industry, while total South African funding was only ~34% of the total, meaning a net inflow of foreign exchange. Likewise, many of the high tech aspects of the project were undertaken by South African industry, including the precision robotic tracking system. This has meant the acquiring of skills previously not present or fully realized in the country.
Finally, SALT, like the science it will produce, has the gift of inspiring the imagination. Young visitors to SALT, and youth encountering SALT in the media or in the classroom, will know that cutting-edge science can happen in southern Africa as well as in the fully developed world. Sparking interest in science in technology, pulling bright young minds into careers in science and technology, is the real future benefit to South Africa.
"Indeed the SALT project has become an iconic symbol for what can be achieved in Science and Technology in the new South Africa." SALT is not simply a South African project, however. It is an international partnership involving 11 different partners from 6 countries on 4 continents – including Germany, Poland, New Zealand, the UK and the USA. A talented team of local engineers and scientists have succeeded in building SALT on a rapid – for big telescope projects at least – 5 year timescale.
More information:
SALTICAM will
be important to research by all the partners involved in building SALT -
(National Research Foundation of South Africa; Nicolaus Copernicus Astronomical
Center of
the Polish Academy of Sciences and a consortium of 3 Polish universities,
comprising:
Jagiellonian University, Nicolaus Copernicus University, and Adam Mickiewicz
University; The
Hobby-Eberly Telescope Board (representing Georg-August-Universität Göttingen,
Ludwig-Maximilians-Universität München, Stanford University, The Pennsylvania State
University,
and The University of Texas at Austin); Rutgers, the State University of New
Jersey (USA);
Georg-August-Universität Göttingen (Germany); The University of
Wisconsin-Madison (USA);University of Canterbury (New Zealand); University of North Carolina-Chapel Hill
(USA);
Dartmouth College (USA); Carnegie Mellon University (USA); United Kingdom SALT
Consortium (UKSC), comprising: the Armagh Observatory, the University of Keele,
the
University of Central Lancashire, the University of Nottingham, the Open
University and the
University of Southampton).
Copyright 2002, Science in Africa, Science magazine for Africa CC. All Rights Reserved
