The SouthernAfrican Large Telescope (SALT), Africa’s largest optical telescope and one of the most powerful in the world, this week turned 20, with an event to commemorate its astronomical excellence and breakthroughs.
This flagship facility for South African and global astronomy was officially inaugurated in 2005 by the then president of the Republic of South Africa, Thabo Mbeki.
SALT is used to study distant stars, galaxies and other celestial objects. Its giant 11-metre mirror, made up of 91 hexagonal segments, allows scientists to collect and analyse light from across the universe. It plays a key role in helping scientists better understand the origins and nature of the universe.
The milestone event was jointly hosted by SALT, the Department of Science, Technology and Innovation (DSTI), and the South African Astronomical Observatory, a national facility of the National Research Foundation (NRF), in Sutherland, Northern Cape, where SALT continues to operate.
It brought together dignitaries, prominent astronomers and scientists, as well as representatives from international partners to reflect on SALT’s scientific impact and legacy.
‘Courageous decision’
Professor Brian Chaboyer, SALT board chairman, said in his welcome address that SALT was the first South African-built optical telescope. He described the decision as courageous on many levels, since previous optical telescopes had all been built outside the country.
“Motivated by an ambitious science white paper from the new government, there was a plan for South Africa to build and operate the largest single optical telescope in the Southern Hemisphere,” said Chaboyer.
Delivering the keynote address, Dr Nomalungelo Gina, deputy minister of science,technology and innovation, said the democratic government’s decision in 1998 to fund SALT’s construction was a defining moment for South African science.
“SALT was built to serve both science and society, linking frontier research with education, technology and socio-economic development. It showed that big science can drive national progress.”
As South Africa looks ahead, Dr Gina reaffirmed the department’s commitment to sustaining and expanding the country’s global leadership in astronomy. “SALT’s 20-year journey is a story of vision, perseverance and excellence. We remain committed to ensuring it continues to shine as a beacon of African science, uniting research, education and innovation for the benefit of humanity.”
SALT is more than a telescope, as it is a symbol of what is possible when vision, investment and international cooperation come together in pursuit of knowledge and progress, Dr Gina noted.
“SALT became the proof of concept, and lessons derived from it were vital to even more ambitious projects, such as the MeerKAT and Square Kilometre Array. Over 20 years, SALT has matured into one of the most scientifically-productive facilities relative to its cost. It has enabled over 600 peer-reviewed publications, produced key discoveries, and collaborated with some of the world’s leading observatories, including Hubble, Swift and ALMA.”
She added that thousands of hours of SALT observation time have supported PhD and MSc research, leading to the development of high-level skills essential for South Africa’s knowledge economy.
“SALT’s 20-yearjourney is a story of vision, perseverance and excellence. I would like to conclude by reaffirming the DSTI’s commitment to sustaining SALT as a beacon of African scientific achievement, one that unites research, education, diplomacy and development under a single national vision.”
Professor Mosa Moshabela, NRF board chairman, emphasised that the conception of SALT was not only a scientific ambition, but a governance decision of courage. “It represented a conviction that South Africa could build and sustain a world-class research facility and, through it, redefine its place in global science.
“Over 50 doctoral theses have been produced using SALT data, and hundreds of students have gained hands-on training at the Observatory. Many of them now occupy leading positions in research and technology, locally and abroad.”
Affectionately known as Africa’s Giant Eye on the Sky, SALT remains the largest single optical telescope in the Southern Hemisphere, capable of detecting light from celestial objects a billion times too faint to be seen with the naked eye, says the NRF.
Originally conceptualised in the late 1990s as a national scientific endeavour, the project became a reality in 1998 when the South African government committed $10 million towards its construction. Completed in 2005, SALT entered full scientific operations in 2011 and has since delivered groundbreaking research that continues to shape our understanding of the universe, adds the NRF.
Key milestones
Over the past two decades, SALT has achieved numerous astronomical milestones, including:
Kilonova of GW170817 (2017): Among the first telescopes to capture the optical afterglow of a neutron star merger, contributing critical data to confirm theories of heavy element formation.
Exoplanet microlensing (2019): Supported the characterisation of newly discovered exoplanets, showcasing SALT’s capacity for rapid follow-up spectroscopy.
Eight super-hot stars unveiled (2020): Identified eight new extremely hot subdwarf stars, advancing understanding of stellar evolution.
“Peekaboo” galaxy discovery (2022): Characterised an ultra-low-metallicity galaxy offering a rare local glimpse into early-Universe conditions.
Four-star multi-stellar system (2023): Confirmed the gravitational binding of a unique quadruple star system, informing theories of multi-star formation.
As SALT embarks on its next decade, the NRF says its partners and international collaborators remain committed to expanding the telescope’s scientific reach and strengthening South Africa’s role as a hub for cutting-edge astronomy.
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