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'First-Light' for Africa's Giant Eye: 1st Colour Images from SALT(Forwarded)



 
 
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Old September 2nd 05, 02:17 AM
Andrew Yee
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Default 'First-Light' for Africa's Giant Eye: 1st Colour Images from SALT(Forwarded)

Southern African Large Telescope
PO Box 9
Observatory
7935
South Africa

Contact persons:
David Laney; Tel.: 2721-447-0025
David Buckley; Tel.: 2721-460-6286
Darragh O'Donoghue; Tel.: 2721-447-0025
Fax: 2721-447-3639

Embargo Date: 1 September 2005, 8 a.m. UT

'First-Light' for Africa's Giant Eye: 1st Colour Images from SALT

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.

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).

Five years ago, on the first day of southern hemisphere spring, a few
hundred people gathered for the SALT ground-breaking ceremony. On a
windswept hilltop near the tiny Karoo town of Sutherland, home since the
early 1970s to SAAO's research telescopes, dignitaries turned the first
soil. Much has happened since that historic day, and SALT is now nearing
completion.

A major recent milestone was the installation in May of the last of the 91
hexagonal mirror segments that comprises SALT's mammoth primary mirror
array, stretching 11 metres across. Another major milestone, which we are
marking today, is attaining "first light" with the telescope's full array
of mirrors and its new imaging camera, SALTICAM. The biggest milestone for
2005 will be the official opening of SALT on 10 November 2005 by South
African President Thabo Mbeki.

An Icon for SciTech Development and Cooperation -- Within Budget

"SALT was an initiative of South African astronomers that won support from
the South African government, not simply because it was a leap forward in
astronomical technology, but because of the host of spin-off benefits it
could bring to the country", said project scientist David Buckley.

"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. Not only that, but the cost of construction has been kept to
within the original budget of $20 million defined in 1998, even before the
final designs were completed.

According to Kobus Meiring, project engineer, "This is due in part to the
fact much of the original design concept for SALT was modeled on the
Hobby-Eberly Telescope in Texas, giving a useful starting point and
allowing SALT's engineers to make creative use of the 'lessons learned'
with the only previous telescope of this type."

Science Achieved and Progress to Come

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. It was Bob Stobie's dedication and
enthusiasm that helped launch, and later steer, the SALT project to
success. His untimely death in May 2002 was felt by all his colleagues,
and the renaming of this major instrument in his name is in recognition of
his major role in the SALT project.

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.

The Information Age Telescope

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 spacebased
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.

Bringing the Stars Home to Africa

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.

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.

The SALT First Light Images

The images we show 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 although this is not yet
operational, the best frames produced by SALT and SALTICAM show star
images as small as 1 arcsecond (1/3600 degree), despite being taken when
the seeing was 0.9-1.0 arcseconds.

From Dr. Phil Charles, Director:

"I am delighted with these First Light images and results that demonstrate
the level of operation we have already attained. Of course, we expect
these capabilities to improve further as the final construction work is
completed and commissioned (particularly the mirror's edge sensors that
maintain the mirror "shape"). To have achieved this within 5 years of the
groundbreaking ceremony is a splendid testament to the efforts of the
entire SALT Project Team, and I give my hearty congratulations to the
Project Manager and Project Scientist, who have set a benchmark for the
entire international community. We look forward with great anticipation to
the first year of SALT science operations."

Information on each of the first light images

1. 47 Tucanae
[http://www.salt.ac.za/content/first_light/PR47tuc.jpg (3MB)]
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. The stars in 47 Tuc are about 10-12 billion
years old, making them among the oldest stars in the galaxy (more than
twice the age of our own sun). Near the centre of 47 Tuc, stars are so
densely packed that solar systems like ours might well be disrupted by
passing stars, and night skies might never be fully dark. Such clusters,
with huge numbers of stars about the same age, are living laboratories for
studies of the life, birth, and death of stars.

2. NGC 6152
[http://www.salt.ac.za/content/first_light/PRngc6152.jpg (3MB)]
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. The camera uses two CCD chips, with a small gap between them.
In the other colour composites in this press release, multiple images have
been combined to remove the gap.

3. NGC6744
[http://www.salt.ac.za/content/first_...ngc6744UBI.jpg (3MB)]
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,
and astronomers in NGC 6744 would probably see a rather sight in their
telescopes if they looked in our direction. Like our galaxy, it contains
more than a hundred thousand million stars. Stars like our own sun are far
too insignificant to show up individually in this picture -- they can only
contribute to the general glow.

The bright nucleus of NGC 6744, as other spiral galaxies, is dominated by
older reddish and yellowish stars, while the widely and thinly spreading
spiral arms are home to bluer and younger stars. Hot star-forming regions,
called HII regions for the ionised hydrogen gas they contain, are evident
as fuzzy blue spots along the spiral arms. Dark lanes and patches show
dust which is obscuring the light of the stars.

This picture clearly shows the enormous light-gathering power of SALT. The
individual colour filter exposures in ultraviolet, blue and infrared
lasted only 10 seconds each, yet the intricate spiral arms, which have
very low surface brightness in this face-on galaxy, stand out clearly in
these short exposures even though there was a 40% illuminated moon in the
sky at the time.

4. The Lagoon Nebula (Central Regions)
[http://www.salt.ac.za/content/first_...agoongreen.jpg (2MB)]
The Lagoon Nebula is a region about 3800 light years away in which stars
of high mass and luminosity are being born, emitting enough ultraviolet
radiation to stimulate atoms in the surrounding gas clouds to emit light.
This eerie glow typical of an "emission nebula" is shown in this colourful
SALTICAM image, produced by combining images in three filters: 120 sec in
U, 20 sec in V and 40 sec in I. The image is about ten arcminutes across
(a third of the apparent width of the full moon in the sky), which
corresponds to about 10 light years at the distance of the Lagoon. The
entire cloud extends over 300 light years, while the region viewed here
includes the youngest stars and the fascinating Hourglass nebula (the
brightest feature in the image).

The enormous light-gathering capability of SALT will allow scientists to
study motions in the gas cloud, as well as other details that may revise
our ideas of how stars are born. We may better understand how stars in the
Lagoon interact with the cloud in which they form, and with previous
generations of stars.

5. NGC 6530 (Lagoon Nebula 2)
[http://www.salt.ac.za/content/first_...c6530green.jpg (3MB)]
NGC 6530 is a cluster of 50-100 stars which formed about 2 million years
ago from the gas clouds of the Lagoon Nebula, a part of which can be seen
in the background. The hottest and most massive cluster member is about
40-50 times as massive as our sun, and is hundreds of thousands of times
brighter.


 




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