The Large Magellanic Cloud is a nearby irregular dwarf galaxy that was the subject of the IRSF’s first research mission.
An aerial view of the site, with the Southern African Large Telescope (Salt) on the left and the IRSF on the far right.
(Image: Tetsuya Nagata, Nagoya University)
The Salt is the largest such instrument in the entire southern hemisphere.
• Anacletta Koloko
Science communication unit, South
African Agency for Science and
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Scientists from Japan, South Africa and other African countries came together in early October at the Space Science Colloquium to share the latest developments in the fields of astronomy, space science and satellite applications.
The event was co-hosted by the national Department of Science and Technology, with the Japanese Embassy in South Africa.
Dr Takahiro Nagayama of Nagoya University filled attendees in on the infrared survey facility (IRSF), a joint Japan-South Africa project located in Sutherland, Northern Cape province, at an altitude of 1 761 metres. Nagayama is the manager of the facility and has been involved with it since its inception in 1998.
The IRSF is situated on the same site as the Southern African Large Telescope (Salt) – the largest optical telescope in the southern hemisphere – and a number of other instruments including the Alan Cousins telescope, the Elizabeth telescope, and the Korean Yonsei telescope. This makes the site one of the best places in the world to conduct advanced astronomy, according to Nagayama.
The IRSF is a 1.4m telescope with an infrared (IR) camera. It was developed by scientists at Nagoya, with the help of the South African Astronomical Observatory (SAAO) and the National Astronomical Observatory of Japan.
It’s Japan’s first southern hemisphere IR telescope. The country decided on South Africa as a host for several reasons.
“We knew we had to build a telescope in the southern hemisphere, because there are many important celestial objects that are only visible in the southern sky,” explained Nagayama.
South Africa was chosen from an initial group of three candidates, with Chile and Australia. It was selected as the best of the three because it had excellent weather as well as an extremely competent astronomical community, and there was no language barrier, as there was in South America.
“The South African people are also very friendly and good to work with. South Africa was the best site for us at that time, and I believe it still is now.”
Japan entered into the agreement with the SAAO in 1998 and soon afterwards, the project received a grant from the Japanese ministry of science and technology, to the tune of some US$7-million.
“The SAAO has provided the infrastructure, including power, water, internet, and the site itself,” said Nagayama. “The local astronomical community built the dome and building.”
Nagoya provided the telescope and near-IR camera known as Sirius, which was developed by graduate students. “You won’t find any big names – Sony, Nikon – in this project,” said Nagayama.
Surveying our skies
Initially, the main function of IRSF was to conduct a thorough study of the Small and Large Magellanic Clouds – small irregular galaxies that lie close to the Milky Way – using a tri-wavelength observation technique.
The Magellanic Cloud survey was completed in 2007 and then the Indian Department of Space used the telescope to survey the central region of the Milky Way. There are other research projects ongoing.
The presence of the IRSF in South Africa has brought the world’s best astronomers to the country and helped to develop its scientific talent. In the 12 years since the telescope came into operation, 142 observers, of whom 81 were Japanese and 61 foreign, have visited from 31 institutes – 13 from Japan, six from South Africa and 12 from other countries including Korea, the UK and US.
Also, studies have resulted in 87 refereed papers, 11 of them with South Africans as the first author. Finally, 19 PhDs have been awarded for research carried out at IRSF, to 16 Japanese scholars and three from the University of Cape Town.
“We hope the collaboration will continue,” said Nagayama. “The IRSF is so far the most successful science collaboration between South Africa and Japan.”
Uncovering the secrets of the universe
Nagayama explained the reasons for choosing to work in infrared instead of visible light.
“Astronomers are interested in concepts such as the possibility of a second earth beyond our solar system, dark energy, black holes, and the dawn and end of the universe,” he said. “Traditionally we have observed these things with visible light, but today we can use the whole electromagnetic spectrum, from gamma rays to radio.”
Probably the most well-known example of this technology, he said, is the Hubble telescope, which has a 2.4m primary mirror and captures images in the near-ultraviolet to near-infrared bands.
The Hubble is in a low earth orbit and because it is not subjected to atmospheric turbulence, said Nagayama, its images are sharp.
However, when taking images of objects that are very far away, visible light does not produce the best pictures. Interstellar dust results in a phenomenon known as scattering of visible light, and the picture that is finally received is degraded, but this doesn’t affect IR as much.
“Also, visible light can’t penetrate the interstellar dust to see into and behind the Milky Way, but IR can,” said Nagayama. “The centre of our galaxy is hidden to visible light, but we can see it clearly in IR because the dust is invisible at these wavelengths.”
Sirius can take simultaneous images in three different bands – wavelengths of 1.2µ (micron), 1.6µ and 2.1µ respectively – because of its special mirrors. The optics are cooled by a closed-cycle refrigerator to about 100 kelvin, or -173 degrees Celsius.
“We can also create a false-colour composite image by colouring the three bands blue, green and red respectively.”
Complementing each other
Nagayama described another major Japanese astronomical project, the Subaru telescope, which is an 8.4m single mirror telescope built on the summit of the volcanic Mount Mauna Kea in Hawaii.
“Although Subaru has a bigger mirror than Hubble and takes good pictures, Hubble is better because it is in space,” said Nagayama.
Other Japanese large projects include the Akari (IR), Suzaku (x-ray) and the Alma radio telescope, while South Africa has the Salt, whose aperture is larger than Subaru, and the KAT-7, MeerKAT and Square Kilometre Array, all of which are projects involving radio telescopes.
Altogether, said Nagayama, this means that the Japanese and South African projects have an observation range from gamma or y-ray, through x-ray, UV, visible light, IR, and radio.
“These projects complement each other,” he said, “meaning that the coverage between Japan and South Africa is effective across the full spectrum of electromagnetic waves.”