Feature

Pass the SALT, Please

New Zealand astronomers hope to join an international group to use a large telescope in South Africa to study the southern sky.

Dr Glen Mackie, Associate Professor Peter Cottrell, Associate Professor Phil Yock

The year is 2005. A giant optical/infrared telescope, the largest in the southern hemisphere, surveys the clear skies above Sutherland, in the high veldt of South Africa. The Southern African Large Telescope (SALT) has been built in the first few years of the new millennium using an innovative design and new optical and mechanical technologies.

SALT is capable of observing proto-planetary systems orbiting other stars, the oldest stars, gamma-ray bursters, newly formed galaxies and the nuclei of luminous quasars with a sensitivity far greater than other telescopes. It is a key instrument in solving many of the questions about the origin and evolution of planets, stars and galaxies, and thus the universe.

Tonight SALT is observing a recently discovered supernova for a New Zealand astronomer, Dr Lana Tinsley from the University of Auckland. She has found slight spectral differences in other distant supernovae, and SALT's large light-gathering capability is allowing her to determine whether such differences are common to these exploding stellar systems. Her observations could have important consequences for results derived in the late 1990s that used distant supernovae as "standard candles" and suggested that the universe would expand forever.

Now let us return to 1998. SALT exists on the drawing board only. It will be a southern version of the existing Hobby-Eberly Telescope (HET) at McDonald Observatory, Texas. HET's unique design has allowed a 10-metre diameter telescope to be built for 20% of the cost of a conventional telescope of the same size. The key design features include a spherical (rather than paraboloid), segmented mirror that is at a fixed elevation to the sky. By moving the telescope in azimuth, 70% of the visible sky can be observed. SALT is the most significant southern hemisphere-initiated optical/infrared astronomical project for many decades.

SALT will be designed with a slightly different elevation from HET to allow it to observe key objects in the rich southern sky, including the Large and Small Magellanic Clouds. SALT, like HET, will be a spectroscopic telescope that records light spread out into its spectral components rather than obtaining an image. Large-aperture spectroscopic telescopes are essential tools that will work in parallel with high performance imaging instruments aboard space-based telescopes such as Hubble Space Telescope (HST) and its successor, the Next Generation Space Telescope (NGST). So whilst HST and NGST produce two-dimensional information, SALT will detect the third dimension (the spectrum of the object), providing important distance and object composition information.

New Zealand astronomers, scientists and technologists at universities, Carter Observatory and Crown Research Institutes propose to join SALT, and will be seeking funds from a range of agencies over the next 6 to 12 months.

The South African Minister of Arts, Culture, Science & Technology, Lionel Mtshali, announced that South Africa has committed $US10 million towards SALT, which would become a flagship science project in the new South Africa. This is half the construction cost of this telescope.

Mtshali notes that "astronomy has played an important role in the lives of people since the dawn of civilisation. Astronomy can, with some justification, be called the first of the sciences. For this reason astronomy plays a powerful role in the public appreciation of science and technology" and that this project "offers us the potential to use our access to the southern skies...to move to the cutting edge of a field which has excited human imagination since time immemorial."

To fund the other half of the construction cost, South Africa is seeking international partners. The South African Foundation for Research Development has noted that "good progress has been made in identifying partners -- potential collaborators include Poland, New Zealand and universities in the [US] and Germany".

South Africa is seeking partners that can guarantee the final 50% of project costs within the next 18 months. Recent international meetings have shown that many potential partners have secured funds to join the project. A narrow window of opportunity exists for other potential collaborators, including New Zealand.

New Zealand Benefits

The New Zealand consortium is seeking partnership in SALT at the 5% level, a viable contribution. Part of our contribution could include a substantial contract to build one of the telescope's initial instruments here, which would provide opportunities for optical design and fabrication within the universities and Crown Research Institutes. The project would provide substantial spin-offs in a number of technological fields -- optical engineering and fabrication and detector technology.

The project would also provide a major boost for the fundamental sciences in New Zealand. This is a unique opportunity to become involved in a big international science and technology project for relatively modest investment.

New Zealand astronomers are well placed to take advantage of SALT's capabilities and to expand their role in southern hemisphere astronomy. Currently astronomers here use small- to medium-sized telescopes at Mount John University Observatory near Lake Tekapo. Future instrumentation and detector upgrades will allow these telescopes to remain internationally competitive with similar sized telescopes.

Large telescopes, however, require the best high-altitude observing sites. SALT offers New Zealand an exciting opportunity to undertake research using a telescope of the largest size.

SALT will allow New Zealand to join the majority of other nations (such as the US, UK, Japan, Australia, Canada and most European countries) involved in astronomical research that have already joined existing large telescope projects such as the European Southern Observatory-Very Large Telescope, Keck I and II, Gemini North and South, HET and Magellan. Some of the research that can be done with SALT includes:

• planetary searches
• studies of the early chemical evolution of our galaxy and its neighbours
• high resolution studies of variable stars
• identification of transient events such as gamma ray bursters and supernovae
• studies of the formation and evolution of normal galaxies
• determining physical processes in active galactic nuclei (e.g., quasars, Seyferts, blazars) that harbour accretion disks and supermassive black holes
• studies of other objects in the distant, early universe

Importantly, these opportunities will allow New Zealand PhD students to be involved in the most up to date astrophysics projects, thus building on our existing reputation of producing world class astronomers.

A Telescope for the New Millennium

There are also science and technology education and promotion possibilities with this project. Information about the telescope and research will be available via the World Wide Web. South Africa has already allocated money to build a new public education and outreach centre near the telescope site. The research carried out with such an instrument could also help promote science and technology careers in New Zealand.

The telescope will be very much an instrument of the new millennium. All observers from the partner countries will submit their observation requirements via the Internet, and the observations will be queue scheduled and completed by astronomers based in South Africa. When the observation has finished, the data will be available via the Internet. This is becoming the normal observing mode for many telescopes. Whilst travel time and money will be saved, some astronomers would insist the "romance" of the science has gone!

Recent discoveries such as gamma ray burster distances, extra-solar planets, microquasars in our galaxy and gravitational lensing by galaxies and clusters of galaxies suggest that SALT will lead the way in discovering similar, new, exotic astronomical objects in the 21st century. We hope that New Zealand scientists and students are along for the exciting ride. For more information about SALT, see the World Wide Web site at http://www.saao.ac.za/salt/

Associate Professor Peter Cottrell is in the Physics and Astronomy Department at Canterbury University.
Dr Glen Mackie is a Senior Astronomer at Carter Observatory.
Associate Professor Phil Yock is a particle physicist at the University of Auckland, and the overall group leader for the MOA project in New Zealand.