Last month my wife and I travelled to Namaqualand for the beautiful annual display of Spring flowers – the best in the world. On our way back to Port Alfred we spent two nights at the South African Astronomical Observatory (SAAO) 14km to the east of the small Karoo town of Sutherland.
On the evening we arrived 15 people came for an outdoor talk under the stars and a look through a small telescope with a resident astronomer. The next day they and others returned for a morning tour of the giant Southern African Large Telescope (SALT), the largest optical telescope in the southern hemisphere.
You, too, can do this, have an introduction to one of the world’s great optical observatories, and see the stars from one of the darkest places on the planet. To find out how to arrange this, see the SAAO website: https://www.saao.ac.za/visit-sutherland/
To visit SALT during the day you can book a guided tour to see this giant telescope. Its main mirror collects light with 91 individual 1-metre diameter mirrors aligned with each other to 50 billionths of a metre! It is a technological marvel.
I have lived my life as an observational astronomer, starting in the 1960s as an undergraduate student observing at the Mt Laguna Observatory near San Diego; then as a PhD student at the McDonald Observatory in West Texas. During my 24 years at UCT, I spent over 200 weeks making research observations with the SAAO telescopes, so Sutherland and the high Karoo are one of my homes. Then, during my 20 years working in England, I travelled to observe with some of the world’s largest telescopes in the Atacama Desert of Chile and from the top of the 4200-metre extinct volcano, Mauna Kea, in Hawaii.
I never tire of the spectacle of the stars from these remote sites where it is so dark you can see your shadow by the light of the Milky Way; where the stars look so close you think you could touch them; where there are so many stars that the familiar constellations are hard to discern.
The SAAO is important in world astronomical research because of the quality of the observing site at 1800 metres above sea level, the large number of clear nights per year, and especially its unique latitude and longitude. When special events happen in the universe – supernova explosions, gamma-ray bursts, colliding neutron stars, planets passing in front of stars – the observations are time-critical, and often SAAO is the only observatory in the world at the right place at the right time.
SAAO operates four telescopes of its own and hosts more than a dozen others built and operated from many other countries. You will see a forest of domes when you visit SAAO.
SALT has a special design so that it only can rotate about its base, but has a fixed tilt angle. This means that observations are timed for when the Earth’s rotation brings objects, such as stars and galaxies, into view. Most other similar-size giant telescopes can point in all directions. The difference is that the 9.2-metre diameter SALT originally cost US$20 million, whereas the 8-metre diameter Very Large Telescope (VLT) in Chile (which I have used) cost US$200 million, and the Japanese 8-metre telescope in Hawaii (which I have also used) cost US$500 million. Both these latter two telescopes cost US$50,000 per night to operate. You might have objected if we astronomers had asked you to spend your tax Rands for these, while we get outstanding value for money with SALT.
The biggest telescopes now cost so much that they can only be funded by many countries joining in a consortium. The world’s biggest telescope, the Extremely Large Telescope (ELT), is now under construction at the European Southern Observatory in Chile with a consortium of 16 member states, plus the host Chile, funding the €1.5 billion (R30 billion) cost!
The 39-metre diameter ELT will have 798 individual 1.4-meter hexagonal mirrors all aligned to within billionths of a metre. It will have actuators that can flex the mirrors 1000 times per second to change their shape to account for distortions caused by the Earth’s atmosphere. It will have better resolution than the Hubble Space Telescope and will collect 250 times more light to see fainter and further into the beginning of the Universe, to image exoplanets around other stars in our search for life in the Universe, and to expand human knowledge.
You will not be able to visit the ELT, but you can see the current biggest telescope built with similar technology right here in South Africa. I encourage you to visit SALT and see the stunning Sutherland skies.
But remember it can be cold. Very cold. In my more than two decades observing at Sutherland, I have seen snow in every month except January and February – even once at Christmas! We had a “snow braai” that time. It can also be hot in summer, so be prepared for just about anything at all times of the year.
- This article was first published in Talk of the Town, September 19, 2024. The newspaper serving the communities of Ndlambe and the Sunshine Coast, with a weekly wrap of Makhanda news, is available at stores from early on Thursdays.
