Mbeki inaugurates 'gigantic African eye' in Karoo

The Southern African Large Telescope (Salt) at the South African Astronomical Observatory outside Sutherland is powerful enough to discern the detail on a R2 coin at a distance of 5km.

The largest single optical telescope in the southern hemisphere, Salt is a modified version of the Hobby-Eberly Telescope at the MacDonald Observatory in Texas in the United States.

Salt will enable the country to remain among the front ranks of those involved in astronomy, President Thabo Mbeki said on Thursday.

Speaking at the inauguration of Salt at the South African Astronomical Observatory near Sutherland in the Northern Cape, he said the global scientific community will benefit greatly from the venture.

“Even those of us who know nothing about astronomy have awaited this day with great anticipation ... that this giant eye in the Karoo will tell us as yet unknown and exciting things about ourselves,” he said.

The inauguration of Salt was attended by about 1 000 guests, including Minister of Science and Technology Mosibudi Mangena; his deputy, Derek Hanekom; and Northern Cape Premier Dipuo Peters.

‘Gigantic African eye’

Referred to by Mbeki as “a gigantic African eye through which we can see the universe”, the 100-tonne instrument has taken five years to build.

It gathers light through an array of 91 hexagonal mirror segments, each with a spherical surface.
Precise positioning of these allows them to function optically as if they were a single 10m surface.

The 13m-long telescope is housed in a specially designed building capped by a 26m-diameter aluminium dome.

Light from objects in Salt’s field of view is relayed via optical fibres to instruments in a basement room below the instrument.

Sixty percent of Salt’s components were made in South Africa.

The engineers who built it boast the concrete ring forming the base of the telescope is the smoothest, flattest piece of concrete cast to date in South Africa, deviating by no more than 1mm from a flat plane over its about 50m circumference.

Remote viewing

Astronomers do not need to visit the telescope to do their stargazing. This is done by dedicated operations staff at the South African Astronomical Observatory, who carry out the observations and then send the data to the astronomer via the internet.

The telescope’s operators say among the distant objects their instrument will be aimed at are stars, galaxies and quasars a billion times too faint to be seen with the unaided eye.

Salt will allow them to study the birth of the earliest galaxies and stars, follow the life cycles and motions of those in neighbouring galaxies and our own Milky Way, and “probe the nature of violent exotic processes in exploding stars, gamma-ray bursters and black holes”.

On September 1 this year, exactly five years after the groundbreaking ceremony marking the start of construction, Salt captured its “first light” images.

Among these were pictures of part of the Lagoon nebula, a region 3 800 light years away in which stars of high mass and luminosity are being born, in the process emitting enough ultraviolet radiation to stimulate atoms in the surrounding gas clouds to emit light.

The total cost of building Salt, according to the Department of Science and Technology, “has been kept within the original estimate of $20-million”.

South Africa contributed a third of this, with the rest coming from partners in Germany, New Zealand, Poland, the United Kingdom and the United States.—Sapa