DESPITE its enviable location under clear southern skies, Australian astronomy has always led a precarious existence. Successive Australian governments have had to be convinced that investment in observatories 鈥� never likely to boost the country鈥檚 balance of payments 鈥� brings the international prestige that major scientific discoveries engender.
Nevertheless a number of major observatories have been built in New South Wales, which has become the prime site for Australian astronomy. Three optical telescopes, including the 3.9-metre Anglo Australian Telescope (AAT), sit on top of Siding Spring Mountain near Coonabarabran. The Australia Telescope (AT), an instrument for radio astronomy, consists of eight antennae at three separate locations spread over 320 kilometres from Narrabri to Parkes in central NSW. The AT array includes the 64-metre radio telescope at Parkes, which these days is being used to search for extraterrestrial intelligence, but in the past pioneered research on the detection of molecules in space and on quasars, the most distant objects in the Universe. In 1990, 20 months after its opening, the AT discovered a supernova, or exploding star, using radio wavelengths. Until then supernovae had only been observed by optical telescopes.
In New South Wales as well, the Advanced Technology Telescope (ATT), operated by the Australian National University, was the first to find organic molecules in the coma of Halley鈥檚 Comet. And at Narrabri, the Sydney University Stellar Interferometer (SUSI) has pioneered work on accurately measuring the diameter of red and blue giant stars.
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But despite these triumphs, Australian astronomy is once again under challenge. The problem is much deeper than securing funds from wary governments. Its very existence is at issue. How can it compete with space-based telescopes that are not prey to the distortions of the Earth鈥檚 atmosphere and with the large, extremely expensive, optical telescopes that are now being built?
The launch in 1990 of NASA鈥檚 Hubble Space Telescope signalled the maturity of space-based astronomy. Suddenly, with orbiting telescopes, astronomy does not rely solely on telescopes in the southern hemisphere to view southern skies. And, after a hiatus of more than 40 years, new materials and designs are making it possible to build optical and infrared telescopes with diameters of 8 metres or more. The best known example is the 10-metre Keck Telescope, which sits atop the extinct volcano of Mauna Kea on the island of Hawaii. Such a large diameter is possible with the use of computer-controlled segmented mirrors rather than a single chunk of glass.
Australia cannot hope to emulate major achievements such as these. Regardless of the cost, the country has no suitable sites for an 8-metre optical and infrared telescope. Moisture in the air absorbs critical infrared wavelengths, and stray light from rural towns is beginning to affect viewing conditions above Siding Spring Mountain at an infinitesimal, but ultimately unwelcome, rate.
The choices confronting Australian astronomy are very simple: improve existing telescopes, build new telescopes, collaborate with other countries, or give the game away. With the country鈥檚 fine record of astronomical achievement, the fourth and last is an unpalatable option to say the least. Australia is certainly following the first and second strategies, and a report due out soon will strongly urge it to follow the third.
This year, after five years of development, great improvements to the AAT鈥檚 instrumentation are taking place. By the end of the year, the telescope will be using a so-called Two-Degree Field (2dF). Its wide angle field of view will increase the amount of sky that can be studied at any one time and, as a result, the rate at which astronomers can explore the Universe. The instrument is based on an array of 400 optical fibres, each of which can be programmed with great accuracy to correspond to the position of a remote galaxy. The light from each of the 400 target galaxies will be split into distinctive spectra and recorded on optical fibres for analysis and identification. 鈥淭he project recognises the changing role of 4-metre telescopes in an era of 8-metre telescopes and shows that significant things can be done on smaller telescopes by thinking laterally,鈥� says Keith Taylor, the AAT鈥檚 head of instrumentation.
One of the first tasks of the 2dF will be to test the standard model of the Universe by trying to establish the relationship between the current distribution of matter in the Universe and the residual microwave radiation released at the time of the Big Bang 鈥� the so-called 鈥渞ipples in time鈥� discovered in 1992 by NASA鈥檚 Cosmic Background Explorer. The instrument will map the distribution of galaxies, at the rate of 400 galaxies at a time, based on their red shift.
Another telescope which has been recently upgraded is SUSI. This interferometer consists of 12 small mirrors spread apart over a distance of 640 metres. It will be able to see the same level of detail as a single-telescope 640 metres across, which is 64 times the diameter of the biggest optical telescope in the world 鈥� the Keck. Designed to collect light from about 100 000 stars within the Milky Way and no more than 10 000 light years away, SUSI will give new information about the structure and formation of stars. It will also provide more accurate measurements of the distances between them.
The most striking example of the successful upgrading of an old telescope has occurred at the Mount Stromlo Observatory on the outskirts of Canberra. The optics from the Great Melbourne Telescope, which was commissioned in 1868, are being used to search for the 鈥渕issing matter鈥� that astronomers believe makes up 90 per cent of the Universe. The old telescope is now controlled by computer and fitted with a sensor capable of producing 64 megabytes of data every 5 minutes. Astronomers are also searching for microlensing events in the Magellanic Clouds. These occur when light passing a massive object is bent by its gravitational field. Under the right conditions, this magnifies the light of a more distant object causing it to flare in intensity. Such an event was detected at Mount Stromlo in October 1993.
The AT may also be in line for an overhaul. A report prepared by the National Committee for Astronomy (NCA) of the Australian Academy of Science is due out shortly that will recommend an upgrading of the AT. The report, Australian Astronomy Beyond 2000, says that the AT should be able to make measurements in wavelengths of 3 millimetres as well as the 10-centimetre wavelengths currently used. 鈥淎t these wavelengths we will be able to look at the movement of warm dust inside galaxies, and the low energy processes in places where stars ignite,鈥� says Ray Norris, head of the astrophysics group at the AT.
The upgrade will cost about A$10 million. If it is done, it will allow the AT to build on earlier discoveries involving the imaging of methanol masers in the dust clouds of embryonic stars. Molecules of methanol in galactic gas clouds emit intense radiation in very narrow frequency ranges turning the molecules into giant masers, the radio equivalent of lasers. 鈥淭hree-millimetre radio astronomy will permit us to look at processes involving carbon monoxide using the very long baselines available to the AT, and greatly improve our understanding of how planets may form around young stars,鈥� says Norris.
At least one new observatory is likely 鈥� the Australian International Gravitational Observatory, to be sited 60 kilometres north of Perth. The observatory 鈥� a gravity wave detector 鈥� will search for bursts of energy associated with black holes and neutron stars, and look for the gravity waves that were predicted by Albert Einstein but have not yet been discovered. Installation of a gravity wave detector has been nominated by a government-appointed panel as one of the big scientific projects that Australia should fund to keep pace with overseas research, but funding is not yet guaranteed. According to David Blair from the University of Western Australia, the governments of India, Argentina and China have agreed to contribute a total of A$9.4 million to the project. The WA government will put in another A$5 million, but a further $8 million is required from the Australian government. Blair is confident that construction will start early next year.
Another project 鈥� the siting of a 2.5-metre infrared telescope on the plateau of the Australian Antarctic Territory 鈥� has the backing of the Beyond 2000 report, but it will not be constructed for at least ten years. According to Michael Burton from the School of Physics at University of New South Wales, a 2.5 -metre telescope at Antarctica would be more than a match for the much larger instruments in Hawaii. 鈥淚t would exploit infrared windows obscured by atmospheric vapour in other locations,鈥� he says.
Over the last two years, a team lead by Burton has been testing sites near the South Pole for the proposed observatory. One promising location, called Dome C, is a spot on the Antarctic icecap which is higher, drier and less windy than the Pole itself. The next stage of the project will be to place an automated observatory on the plateau to verify the viewing characteristics over time.
Burton believes that Australia should also participate in international plans to tether 8-metre optical infrared telescopes to balloons in the atmosphere above a support tase on the plateau. 鈥淭his requires a pointing ability accurate to fractions of an arc second, but the technology appears to be achievable,鈥� he says.
According to the report, Australia risks falling behind in astronomy because it is not engaging in enough international collaboration. It mentions the country鈥檚 recent failure to accept an invitation to join the consortium of European nations in the European Southern Observatory (ESO) as one significant example. The ESO was formed in 1965 to operate telescopes in Chile. Australia was invited to become a full member in January last year 鈥� for an initial fee of A$11 million and an annual fee of A$5 million 鈥� to participate in its Very Large Telescope (VLT) project at Cerro Paranal in Chile鈥檚 Antacama Desert. The VLT consists of an array of four 8-metre telescopes. The first will come in 1998.
The Beyond 2000 report says that Australian astronomers need to have access to a facility like the VLT if they wish to remain internationally competitive. Current problems faced by the country鈥檚 astronomers include the fact that viewing time at Australia鈥檚 main observatories is often chronically oversubscribed. At the AAT, for example, the request for time on the telescope can be four times greater than the viewing time available.
The report makes its pitch to the government in economic terms as well. It says ESO membership will benefit the economy because of the industrial innovation that will be required to enable Australia to participate in highly competitive, world class astronomical research. Opportunities will arise for Australian industry in fields such as robotics, electronics, specialised instrumentatation and image processing software.
If Australia鈥檚 astronomers are granted two of their wishes 鈥� participation in ESO and an upgrade of the AT 鈥� it will be possible to form a vast baseline array for radio astronomy, stretching from Chile to New South Wales. The ESO plan to construct a large submillimetre wavelength array at Cerro Paranal by early next century.
The NCA report says that Australia must join the ESO 鈥� at the fee on offer 鈥� if it wants to be part of astronomy鈥檚 new world order. The fee is cheap compared to what it would cost the country to go it alone. The NCA recommends that A$110 million be spent between now and the year 2000 so that Australia can participate as an equal partner in large scale projects such as the VLT. Australia should also build new telescopes and continue to upgrade existing facilities where possible. Other proposals worth investigating are a 1-kilometre square radio telescope based in either the Gibson or Great Stony deserts and a share of the International Cosmic Ray Observatory, if it is sited in Australia. The stark alternative to a substantial investment is the relegation of the country鈥檚 telescopes to tourist attractions of historical relevance only.
First light
THE sixth governor of the colony of New South Wales. Thomas Makdougall Brisbane, was a military man. He attained the post of Brigadier-General after leading British troops in France, the West Indies and in America. Brisbane was also an amateur astronomer. With his own money, he built an observatory at Parramatta, not far from Port Jackson where Austtralia was first settled. In June 1822, just a few weeks after it was commissioned, the observatory was the first in the world to witness the predicted return on Encke鈥檚 comet. NSW has remained at the centre of astronomy in Australia.