The Australian Large Telescope Project
Electro Optic Systems Pty Ltd
The National Committee for Astronomy
of the Australian Academy of Science
For consideration by
The Minister for Industry, Science & Resources
Like buried treasures the outposts of the Universe have beckoned to
the adventurous from immemorial times.
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George Ellery Hale 1868-1938.
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Australia has a unique opportunity to form and lead an international partnership to
build and operate a wide field 6.6 metre optical and infrared telescope.
Benefits to Australia
Participation in the Australian Large Telescope (ALT) project will benefit Australia in
• Australian scientists will compete with their international colleagues on a level
playing field in the new era of large telescopes and will make many of the discoveries
which will stream from the largest wide field optical/infrared telescope in the world.
• Australian industry will participate in building the ALT and its leading-edge
scientific instruments. An Australian company of international standing will lead the
project, which will be a model for the development of a knowledge-based economy in
• The high visibility of Australian discoveries in astronomy will continue to be a
source of national pride. This will both encourage young people to pursue careers in
science and engineering and help to equip them for those careers.
The ALT is a project of Electro Optic Systems Pty Ltd. EOS undertakes to build and
operate the telescope for the partners. The partners undertake to equip the telescope
with scientific instruments. A $30M AUD grant from the Department of Industry,
Science and Resources is sought to purchase a 50% share in the partnership for
Australia. Australian universities will need a further $5M AUD of support from DETYA
to build their share of the instruments.
Twenty five years of research with 4-metre telescopes like the AAT have produced a
wealth of discoveries, but, as is often the case in a young science, at least as many new
questions have been asked, as have been answered.
What were the physical conditions of the early universe ? How did galaxies form from
the material in that state ? How will the large scale structure of the universe evolve ?
What is the nature and distribution of dark matter ? What powers quasars ? How do
stars and star clusters form ? What is the internal structure of stars ?
To tackle these astrophysical problems, the ALT will provide excellence in spectroscopy
over the full range of wavelengths accessible from the ground (300 nm to 30 m). The
ALT will do this in conjunction with the Gemini 8 metre telescopes, complementing
Gemini’s small field with a wide field of a hundred times the area, and making
maximum use of the multiplex advantage. Australia has only a 5% share of the two
Gemini telescopes, but should have a majority share of the ALT.
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1. The Large Telescopes Era
1.1 Collecting Area and Field Size
In 1609, Galileo first turned his crude telescope towards the night sky. His observations
of such diverse objects as lunar craters, planetary disks, the satellites of Jupiter, and the
Milky Way revolutionized the physical sciences and our understanding of the universe
we live in. Since Galileo's day there have been enormous advances in telescope
technology and performance. Steady gains have been both in the collecting area and
image quality of optical telescopes.
The collecting area of a telescope is determined by the diameter of the primary mirror,
which is also called the telescope aperture. Telescope aperture has increased
exponentially since Galileo's first instrument, with a doubling of aperture every 60
years between 1610 and the present day. Progress in optics, glass technology, figuring
and polishing has increased resolution from the naked eye value of 100 arcsec to the
sub-arcsec resolution of superior high-altitude sites (1 arcsec = 1/3600 degree).
Fig. 1. The aperture of a telescope is the diameter of the primary mirror. In the case of the Gemini
telescope pictured here, that is 8 metres.
The field size of a telescope is the area of the sky which can be imaged in one pointing. In
1993 the Anglo Australian Telescope introduced new optics which imaged a 2 degree
field. Instrumenting the 2 degree field allowed the AAT to conduct the largest galaxy
redshift survey ever undertaken and to accurately determine the density of the
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Fig. 2. The field size of a telescope determines how much of the sky can be analyzed simultaneously. The
2dF spectrograph on the AAT is shown here.]
Two factors are responsible for the recent dramatic improvement in the quality of our
optical and infrared observations. They are:
• advances in technology which have allowed us to construct telescopes with
apertures larger than 4 metres (e.g. thin lightweight primary mirrors, computer
controlled mirror support systems and alt-azimuth mounts, sophisticated active
and adaptive optics, and the latest opto-electronic detectors);
• growing experience in operating telescopes able to exploit the superb seeing at
superior sites (for example, the Canada-France-Hawaii Telescope on Mauna Kea,
Hawaii, and the Very Large Telescope (VLT) on Cerro Paranal, Chile).
1.2 Australia's Position
It is now twenty-five years since the Anglo-Australian Telescope (AAT) project was
completed. Over these decades, optical astronomy has been a vital Australian research
area. Our contributions in optical astronomy have attracted world-wide recognition for
their excellence. The success of the AAT has been due not only to its excellent
instrumentation, support staff and management, but also to the access it provides for
the detailed astrophysical study of objects in the southern skies. Australians have
enjoyed a particular advantage through our further access to smaller optical telescopes,
which has allowed the background work on observational projects before the allocation
of the valuable resources at the AAT. Even more importantly, radio data obtained with
the facilities at Sydney, Parkes, Tidbinbilla and Narrabri have been vital in creating our
competitive edge. Finally, Australian researchers using the AAT have performed
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important and highly successful follow-up observations of sources discovered by space
satellites operating at IR, UV or X-ray wavelengths.
At radio frequencies, our capability to provide state-of-the-art data on southern sources
is now unrivalled, thanks to the construction of the Australia Telescope. However, for
astrophysical research at optical wavelengths, Australia now stands at a new threshold.
Decisions made now will prove crucial to the continuing health, or even to the future
survival of optical astronomy in Australia.
This challenge is caused by the success of the new generation of large optical telescopes,
made possible by technological breakthroughs in optical fabrication and structural
design. A number of international projects are complete or in an advanced state of
construction. Examples are:
• The Keck telescope (two 10m telescopes) in Hawaii, operational since 1993.
• The VLT, four 8m telescopes in Chile, operated by the European Southern
Observatory. The Australian Government opted not to join this partnership in
• The Gemini project, twin 8m telescopes, one in the south and one in the north.
The Australian Research Council is a 5% partner in this project.
The first telescope was opened in June 1999, the second will open in 2001.
• The Japanese National Large Telescope, an 8m telescope in Hawaii.
• The Magellan and Columbus projects, 6.5 or 8m-class instruments under
To remain competitive, Australian astronomers need the same level of access to
telescopes of this class as astronomers in other OECD nations. In 1994 the National
Committee for Astronomy of the Australian Academy of Science recommended in
Australian Astronomy: Beyond 2000, its decade plan for 1995-2004, that Australia join ESO
in order to participate in the VLT project. In December 1995 the government of the day
failed to take up this recommendation, seeing ESO as a largely overseas enterprise. In
February 1996 the Australian Research Council was able to gain membership of the
Gemini project, but not the same level of access that ESO would have offered. The
shortfall, when the VLT and Gemini are completed in 2001, will be 110% of our Gemini
In this context the National Committee for Astronomy supports the initiative of an
Australian company to form a new partnership with Australia holding the controlling
interest. The Australian Large Telescope Project aims to build and operate a 6.6 metre
telescope at a site with excellent astronomical image quality. The telescope should
complement Gemini scientifically, that is, its competitive advantage should be in
research areas for which Gemini has not been optimised. It should also correct the
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2. EOS and the ALT
Electro Optic Systems Pty Ltd has spent the past twelve years in the telescope and
satellite laser ranging business. Over the past five years the construction of
astronomical telescopes has become a major part of the business plan. In 1996 EOS
delivered six one-metre telescopes for Satellite Laser Ranging, five to the
Communications Research Laboratory in Japan and one to Auslig, the Australian
National Mapping Bureau. This year EOS will deliver two 2 metre astronomical
telescopes to the University of Tokyo and to the Indian Institute of Astrophysics. In the
year 2000, EOS will deliver a further four 1.8 metre telescopes to the California
Association for Research in Astronomy (CARA) and the W.M. Keck Observatory. These
“outrigger” telescopes form part of the Keck Interferometer, and are built to the some of
the most demanding specifications ever achieved in astronomical telescopes.
The completion of this prestigious project in 2000 will place EOS amongst the world
leaders in astronomical telescope technology, and it is the intention of the company to
dominate the world in this field within the next few years. EOS has managed to
produce a new class of product with superior performance and significantly reduced
price. This is achieved largely through excellence in design and management, with the
efficient operation of a small, lean, yet aggressive Australian company. Telescope
construction has been transformed by EOS into a commercial commodity, rather than
an individual research project.
It is anticipated that there will be a steady market for the 2 metre class telescope in the
future, and EOS is now able to bring the same qualities to the large telescope (6 metre
market), and bring the ownership of such telescopes within the scope of modest
budgets. The Australian Large 6.6m Telescope will be but the first of a series of
telescopes. Once the cost versus performance benefit has been demonstrated by the
ALT, our market research indicates customers for at least two more telescopes of this
class in the immediate future (within 3 years). Following this we will continue to
market the affordable large telescope and anticipate sales of another 5 within the
EOS provides a turn-key solution: the total telescope, observatory and control package
is provided and managed by EOS. EOS can also maintain the telescopes after
installation, if required. This allows the EOS engineers to do what they do best (that is
build superior telescopes for the lowest possible price) while providing state of the art
tools to the scientists and allowing them to do what they do best, making astronomical
discoveries. The construction of the ALT provides for the optimum efficiency and
return to Australian Industry, Science and Engineering. Australian Engineering gains a
reputation as the world leader in this high-technology arena, Australian Industry enjoys
the returns from building not just one, but a number of large telescopes in Australia,
and Australian Science gain access to a unique, world-class facility.
Through co-operation with other project partners, Australia also cements its place in the
world community and creates bridges for other involvement in science and technology.
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2.1.1 Australian Manufacturing Share of ALT
The ALT project is estimated at a total of USD 40 M. The composition of this is
apportioned approximately as in Table 1. EOS would construct as much as possible of
the telescope and observatory in Australia, except for components for which Australia
has no current capability.
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Table 1: Cost Breakdown and Likely Source of Manufacture
Cost USD Cost USD % Manufacture
Telescope 26,000,000 65
- design 1,000,000 2.5 Australia/US
- structure 10,000,000 25 Australia
- optics 11,000,000 27.5 US/Germany
- controls 1,500,000 3.75 Australia
- software 1,000,000 2.5 Australia
- installation 1,500,000 3.75 Australia
Observatory 7,500,000 18.75
- design 1,000,000 2.5 Australia
- dome 4,000,000 10.0 Australia or partner
- ring wall 2,000,000 5.0 Australia or partner
- controls 500,000 1.25 Australia
Site Costs 5,000,000 12.5
- pier & foundations 2,500,000 6.25 Australia or partner
- infrastructure 2,500,000 6.25 Australia or partner
Project Management 1,500,000 3.75 Australia
(*)depending on various partner contributions
The main item that must be produced overseas is the optics. Items denoted with a (*)
could be provided by Australia, or by one of the project partners, depending on the
return required by the partner organizations. For the ALT and subsequent programs,
EOS undertakes the design and project management of the components, but the actual
manufacture is largely subcontracted to Australian engineering firms. In this way,
Australian industry benefits not only from a significant volume of work, but also
exposure to state-of-the-art technology and future sales.
Subsequent telescope projects would exhibit a similar proportion of work, even though
Australian funding contribution to these projects would be zero. That is, up to 70% of
future telescope project funds could be spent in Australia, with Australian Industry.
This proposal requests the backing of Australian Industry and Science by its
Government, to the level of a 50% share in one telescope (i.e. USD 20M). On current
projections Australian Industry could expect to win at least USD 20M from the ALT and
USD 60M work from the proposed three telescopes. Returns to industry of up to USD
150M from subsequent sales could be anticipated. An additional USD 5M is required
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from the Universities’ funding agency to allow them to equip the ALT with the
Australian share of the telescope’s instrument complement. See Appendix B.
2.2 Figures of Merit for Large Optical / IR Telescopes
Astronomers build larger telescopes for a simple reason: to detect objects which are too
faint or too small to see with lesser telescopes. Small, faint objects are often more
distant and, because of the finite time light takes to travel through space, are seen as
they were billions of years ago.
When seeking faint objects, the power of larger diameter telescopes is illustrated simply
by the case of a point source of light seen against a uniform background (footnote 1).
Consider directing the 4-metre Anglo-Australian Telescope and the 6.6-metre ALT
towards the same point-like source, e.g. the matter falling into a black hole at the
nucleus of an active galaxy. As a result of the larger size of the ALT, and the superior
atmospheric conditions at Hanle or Mauna Kea, the ALT will detect such a source at a
distance twice as far as the AAT. Galaxies seen as they were 3 billion years ago by the
AAT can be studied in their infancy up to 6 billion years ago by the ALT.1
2.3 Comparing the ALT with its Peers
The ALT will have an overwhelmingly large field compared with any of the new
generation of large telescopes. A optical design has been developed which gives a field
of 1.2 degrees. A multi-object spectrograph exploiting this field will have a factor of a
hundred multiplex advantage over GMOS, the equivalent instrument on the Gemini
For narrow-field observations the Gemini telescopes will have a relatively modest
advantage over the ALT of 20% in signal-to-noise ratio per unit time or 40% in time, to a
certain specified signal-to-noise.
For observations in the very small field, in which adaptive optics can be employed to
deliver diffraction limited images, the Gemini telescopes will have a large advantage
over the wide-field ALT.
At optical wavelengths, the apparent angular diameter (s) of a point source is determined by the effects
of turbulence in the Earth's atmosphere (seeing). Since the detected signal from an optical/infrared
telescope of diameter D is proportional to D2, while the noise from the sky background is proportional to
D x s, the signal-to-noise ratio from a unit time observation is proportional to D/s.
Using D/s as the figure of merit for large telescopes at sites characterized by their median seeing, and
measuring D in metres and s in arcsec, a 4-m telescope at a site with 1.5 arcsec seeing scores 2.7. By
comparison, a 16-m telescope at a site with 0.5 arcsec seeing scores 32. It follows that in a given exposure
time, sources 12 times fainter will be detected by the larger telescope. If astronomical sources are
"standard candles" (all the same brightness), the larger telescope will detect the source 3.5 times further
In the thermal infrared and submillimetre regions of the spectrum images are diffraction limited. The
figure of merit is just D2. The performance ratios favour large telescopes even more strongly.
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In budgetary terms the ALT compares well with the Magellan 6.5 metre telescope of the
Carnegie-Harvard-Arizona-MIT consortium. This will have first light later this year.
2.4 Complementarity with Australian Astronomical Facilities
The front ranking optical/infrared astronomical facility in Australia is the 4m Anglo-
Australian telescope, operated together with the UK Schmidt telescope by the bi-
national Anglo-Australian Telescope Board. These national facilities are located on
Siding Spring Mountain, together with the Australian National University's (ANU)
2.3m, the largest wholly-controlled Australian optical/infrared telescope.
The Australia Telescope National Facility, consisting of the 6 km Compact Array at
Narrabri and the Parkes and Coonabarabran radiotelescopes, is the largest and most
versatile group of radiotelescopes in the southern hemisphere.
2.5 Useful Lifetime
An astronomical telescope is an extremely versatile tool which can support a diverse
range of research activities, depending on its attached instrumentation. This versatility
can lead to a productive life of fifty years or more, even in the face of major
technological changes. This ensures the maximum return on the initial investment.
For example, a telescope built as long ago as 1868 (the Great Melbourne Telescope now
at Mt. Stromlo Observatory) can make frontline discoveries, as the GMT did in October
1993 with the detection of a transient gravitational lensing event due to a MACHO
(massive compact halo object). Older telescopes are still highly productive scientifically
because of the introduction of new state-of-the-art instruments. Their usefulness is often
cut short not by obsolescence, but rather by the encroachment of urban sprawl and light
pollution. The ALT site will be selected for, among other factors, isolation from urban
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3. Science Highlights
As noted in the 1995 review "Australian Astronomy: Beyond 2000", Australian
Astronomers have a well deserved international reputation as leaders in many areas of
Astronomy. This stature has been maintained for three decades or more by two factors.
First, our location gives us access to the Southern skies where-in lie our nearest galactic
neighbours, the Magellanic Clouds, the star fields of the Galactic Centre, and the
nearest and brightest examples of both the oldest and the youngest stellar components
of our Galaxy. Second, and more importantly, Australian Astronomers and their
students have always enjoyed guaranteed access to front-rank facilities whose
telescopes and instrumentation provide the tools to tackle the high priority scientific
issues of the day.
In this section we highlight some the science that will flow from the ALT, one of the
premier large telescope projects in the world.
3.2 The ALT as a Probe of Evolution of the Universe
The appeal of astronomy to the human imagination goes beyond wonder about the
immensity of space and curiosity about what exists in the Universe. An additional
dimension of cosmic time has entered Astronomy in the twentieth century. We have
learned that stars evolve, galaxies evolve and that the Universe itself has a history
which we can read. The ALT will open earlier chapters in this history than we have
managed to read up to now. From these earliest chapters we may learn much about
fundamental physics, because, for example, we do not understand how the structure in
the Universe that we see today arose from the apparent simplicity of the Big Bang.
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Fig. 3. Astronomy probes cosmic time. The dark zone is the interval of time between the formation of the
earliest structures seen by COBE and the highest redshift galaxies seen optically.
Since they are the brightest beacons in the Universe, the light from the most distant
quasars traverses the Universe from epochs when it was less than 10% of its present
The high redshift cutoff in quasars (Fig. 4) is not well understood. Is most of the high
redshift population perhaps hidden by dust? A spectroscopic survey of a few square
degrees with the ALT will test that hypothesis. The required near-infrared imaging on
which to base this survey will be done with the AAT.
Fig. 4. The redshift distribution in the AAO’s 2dF Quasar Survey, courtesy B. Boyle and R. Smith. The
ALT will probe the reasons for the decline in numbers at high Z.
3.2.2 The Future of the Universe
A supernova is the spectacular manifestation of the death of certain types of stars. In a
supernova the core of a star implodes in seconds causing the envelope to explode so
violently that in a matter of weeks the supernova releases more energy than the Sun
liberates in its lifetime. Because of this enormous energy release, supernovae are bright
enough to be seen across vast distances in the Universe. For certain types of supernova,
there is observational evidence that the maximum intrinsic brightness is constant from
supernova to supernova. Thus in this situation it is possible to regard such supernovae
as "standard candles". Peering more than halfway across the Universe to analyse light
from exploded stars the high-Z Supernova Search can answer the question, over cosmic
distances does light travel in straight lines? The results to date, hailed by Science
Magazine in 1998 as the breakthrough of the year, are that the expansion of the cosmos
has not slowed since the initial impetus of the Big Bang and, thus, should continue to
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balloon outward indefinitely. The observations appear to show that the Universe is
accelerating, indicating that a repulsive force is at work, countering gravity. The
observers currently assume that absorption by dust does not affect their results. This
needs investigation by means of near infrared supernova surveys with the ALT. The
ALT will again work with the AAT in studies of this nature by enabling spectroscopic
follow-up of discoveries for confirmation of their nature.
Fig. 5. In 1987 a massive star in the Large Magellanic Cloud, our nearest galactic neighbour, ended its life
in a gigantic explosion that was designated supernova 1987a. At its brightest this supernova was clearly
visible with the unaided eye, being approximately 40,000 time brighter than its progenitor.
3.3 The ALT as a probe of the evolution of galaxies
3.3.1 Distant Galaxy Formation and Evolution
How and when galaxies formed and the evolutionary processes that subsequently
shaped them is one of the key questions of modern cosmology. The formation and
evolution of galaxies represents a fundamental but poorly understood transition
between the homogeneous Universe that was produced by the Big Bang, and the
present state in which the familiar astrophysical processes involving stars, planets and
gas clouds take place. In trying to unravel the history of galaxy formation, astronomers
have a distinct advantage over other historians in that they are able to look back in time
directly. With the existing 4m class telescopes, normal galaxies like our own can be
studied out to distances so remote that the light seen from these objects left them when
the Universe was almost half its present age.
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Fig. 6. Artist’s impression of ALMA (Atacama Large Millmeter Array)
The galaxy formation epoch itself will be unlocked in the next decade by submillimetre
and redshifted neutral hydrogen imaging with the Atacama Large Millimetre Array
and the Square Kilometre Array. The ALT will complement these facilities with a 1.2
degree field for infrared redshift determination of submillimetre sources.
A parallel program of equal importance will be to undertake extensive spectroscopic
surveys of galaxies at brightnesses fainter than that charted by the 4m class telescopes.
Spectroscopy allows a two-pronged attack in that it unambiguously provides a distance
estimate for a galaxy as well as spectral information of sufficient detail to ascertain the
physical processes going on within the galaxy.
Photometric surveys of field galaxies with 4m telescopes have shown that there are
many more faint blue galaxies than models predict and there is a monotonic trend
towards bluer colours with increasing faintness. It is tempting to interpret these blue
galaxies as very distant objects seen at much earlier epochs when their star formation
rates were significantly higher. However, in the absence of any distance information,
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an equally feasible hypothesis is that they are a hitherto undiscovered population of
low luminosity dwarf galaxies at relatively nearby distances. Only spectra can resolve
this issue: the ALT with an efficient multi-object spectrograph would have the
capability of observing the many hundreds of faint galaxies necessary to produce a
convincing statistical result.
3.3.2 The Formation of Clusters of Galaxies
X-ray gas marks the site of the first clusters of galaxies to form. The gas is in thermal
equilibrium with the gravitational potential of the clusters. The ALT will complement
new surveys by the x-ray satellites XMM and AXAF.
Fig. 7. X-ray emission from the nearest cluster of galaxies in Virgo. This map is from the ROSAT satellite.
3.4 The ALT as a Probe of Evolution of Stars
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3.4.1 Star Formation Regions
Fig. 8. The closest region of star formation in Orion. Picture courtesy, M. Bessell, ANU.
Understanding the formation of stars and planets is one of the most important and
fundamental unsolved problems in astrophysics. A knowledge of star formation is
central to our understanding of star clusters, galaxy evolution, the build-up of the
chemical elements, planetary formation, and even the origins of life itself. Much has
recently been learned about the conditions under which stars form from observations
made with infrared imaging systems on 4m class telescopes. Yet fundamental questions
remain concerning the distribution with mass of the forming stars (e.g. how many one-
third solar mass stars form for every solar mass star, etc.) and whether this mass
distribution, known as the initial mass function, varies with environment. The processes
by which clouds of cool gas collapse and fragment to form stars are also only poorly
understood, as indeed are the origins of star clusters and the conditions under which
high mass stars form, to name but a few of the unsolved problems in this area. These
though are the priority issues in the subject of star formation and they will be amenable
to direct investigation with the infrared spectrograph of the ALT.
3.5 The Nature of Dark Matter
3.5.1 Brown Dwarfs
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The initial mass function for stars is a basic parameter relevant to many areas of
astronomy, including chemical enrichment studies, and the nature of dark matter in
galaxies. Low mass stars quietly fade to obscurity leaving most of their mass locked-up
in a low-luminosity remnant. Clearly the amount of mass contained in low-luminosity
remnants and the amount of heavy elements added to the interstellar gas per stellar
generation is strongly dependent on the form of the initial mass function. Yet we have
little understanding of how this function is set up and how it is influenced by local
conditions. However, with the wide field, high sensitivity infrared spectroscopic
capabilities of the ALT, we will be able to characterise the stellar initial mass function in
a variety of environments and over a large range in stellar mass. Environmental factors
influencing the form of function can then be studied and the high and low mass limits
to the stars formed identified. This will then lead ultimately to an increased
understanding of the complexities of the star formation process.
The search for brown dwarfs in nearby star clusters will be pursued with great
efficiency by the ALT.
Fig. 9. The star cluster K Cru. Photo: M. Bessell
3.5.2 Galaxy Halos
Before galaxies formed, the gravitational potential wells of galaxies condensed from
concentrations of dark matter. We know little about the potential wells which hold
galaxies together. A field size much larger than Gemini’s is required in order to
measure the motions of objects such as planetary nebulae far from the centres of nearby
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Fig. 10. The dark mass within the halo of the Milky Way remains uncertain. The ALT will dynamically
probe the halos of nearby galaxies for dark matter.
3.5.3 Gravitational Lenses
Some sixty years ago, the astrophysicist Fritz Zwicky had the remarkable insight to
realize that large clusters of galaxies have enough mass to bend light rays. Thus they
could act as giant lenses enabling us to use clusters as natural telescopes to see great
distances across the universe. These gravitational lenses however, produce distorted
images; in most cases a background galaxy is imaged into the form of arc though if the
alignment is appropriate, the background object can be imaged into an Einstein ring.
Zwicky also predicted that the effects of gravitational lensing would allow us to
measure the amount of matter in the cluster itself, a measurement which is difficult by
any other method since it appears that most of the cluster mass is in the form of "dark
matter", that is matter which does not emit any detectable light.
But it was not until 1985 that Zwicky's predictions were confirmed. With the advent of
high efficiency detectors it was possible to see for the first time distorted images of
background galaxies around a cluster of galaxies which was itself halfway across the
universe. From the geometry of the gravitational lensing effect, we know that these
background images must be even more distant than the cluster, both in time and space.
Thus by this technique we are able to directly select a sample of very distant galaxies for
study, something that is not easily achieved in other ways. As well, the observed effects
of the gravitational lensing can be used measure the distribution of mass in the cluster.
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Fig. 11 shows a ~2hr red exposure taken by Warrick Couch, UNSW, and his colleagues of the rich galaxy
cluster Abell 2218 using the Wide Field and Planetary Camera-2 on the Hubble Space Telescope. The
highly conspicuous arc-like features spread across the image are due to the lensing effect of the
enormously strongly gravitational field of the cluster. It acts like an enormous gravitational telescope,
which magnifies, brightens and distorts images of objects that lie far beyond it. The arcs are the distorted
images of a very distant galaxy population which is about two times farther away than the lensing cluster,
which is itself at a distance of ~2.5 billion light years. The arcs provide a direct glimpse of how star
forming regions are distributed in remote galaxies, and other clues to the early evolution of galaxies. The
abundance of lensing features in Abell 2218 has also been used to make a detailed map of the distribution
of matter (both luminous and dark) within the cluster.
While images such as that depicted can be obtained with 4m class telescopes at excellent
sites, the follow-up spectroscopic studies of the gravitationally lensed images of the
background galaxies, which are needed to tell us their distance and evolutionary state
for example, are almost impossible to obtain with anything but an 8m class telescope.
We can be confident then that this will be one area of Astronomy where the superb
optics and enormous light gathering power of the ALT will make a revolutionary
The Australian Large Telescope Project will allow Australian astronomers and their
students, and indeed the Australian public as a whole, to share in the exciting
discoveries that will flow from the ALT in the next decade. While the above sections list
a number of scientific questions that will be answered with the ALT, it should be kept in
mind that ever since Galileo turned his crude telescope to the Milky Way and
discovered it to be made of a myriad of stars, the greatest discoveries to come from new
instruments are those that were not expected or anticipated. There is no doubt this will
also be the case for the ALT. Clancy's vision splendid epitomizes the appeal of
Astronomy to both the scientist and the public as a whole:
"and at night the wondrous glory of the everlasting stars"
A. Banjo Paterson, Clancy of the Overflow
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Primary mission: Visible and Near Infrared Wide-Field Imaging and Multi-Object Spectroscopy.
• Primary Mirror Aperture 6.6m
• Primary Focal Ratio f1.7
• Optical Design Ritchey-Chretien
• Telescope Focal Ratio f6
• Secondary Mirror Aperture 1.87m
• Secondary Obscuration 8% of primary aperture
• Focal Positions Cassegrain, with back focal
- for use with a tertiary flat mirror and support
4 for up to 4 instruments
5 Nasmyth possibly not excluded
Field of View
• Field of View (corrected).
1.2 degrees with 0.3 arcsec (rms) or better image quality.
• Field of View (uncorrected).
>10 arcminutes with 0.3 arcsec (rms) or better image quality.
>2 arcminutes with 0.1 arcsec (rms) or better.
• Two element corrector, with telecentric field curvature (approx 0.6m diam).
• Atmospheric dispersion corrector (if required).
• Low order aberration correction and control on secondary (not tip/tilt).
• Plate Scale 5.2”/mm
• Absolute Pointing ~1 arcsec.
• Tracking Resolution <0.1 arcsec rms over 1 minute (goal).
<0.3 arcsec rms over 1 hour (goal).
• Encoder Resolution 0.01 arcsec.
• 24m dome with integral aluminizing plant. Active seeing control measures.
• Remote operation of telescope and observatory.
• Latitude 20˚31’N 30˚13’S
• Longitude 155˚53’W 70˚42’W
• Altitude metres (feet) 4200 (13,780) 2715 (8,907)
• Seeing, Median @ 550nm 0.46 arcsec 0.6 arcsec
• Precipitable Water Vapor 1-2mm 2mm winter
• Spectroscopic Nights/yr ~250 ~280
• Photometric Nights/yr ~180 ~220
• Annual Precipitation. Cm <35 <22
• Diurnal Temp. Range 10˚C 15˚C
• Humidity; median 25% ~25%
• Temp. average night +2˚C +4˚C
• Wind; average night ~6.5m/s ~7.2m/s
Alt/altp/fa 21 28/11/11 11:43
Appendix B: Instrumentation for the ALT
1) a 25 arcminute multi-slit LDSS-style spectrograph. We anticipate that the AAO would
carry out a design study for construction of a $2M instrument.
2) an intermediate resolution optical or optical+ir or IR spectrograph.
The ANDES instrument, proposed to ARC for construction starting in 2000 would be a suitable
prototype. ANDES is the next generation 2dF multiobject spectrograph.
Estimated cost: $3M plus $1.1M of in-kind contributions (labour) from universities.
Summary. Two instruments are required, and one of these should be built in Australia at a cost
of $5M of new funding and $1.1M of labour contributed by universities. The other one should be
contributed by the other partners.
Fig. 12 A cut-away view of the ANDES spectrograph configured for a Nasmyth focus.
The ALT would require a Cassegrain configuration.
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