SA astronomy has a rich history and a promising future

Ian Glass, associate research astronomer at the South African Astronomical Observatory, writes about the pioneering work that has been done over the past few decades by astronomers in South Africa.

- Ian Glass

The South African Astronomical Observatory in Cape Town turned 200 last year and it is the oldest permanent observatory in the Southern Hemisphere. This observatory is a fundamental part of South Africa’s long history of astronomical research, which began when French academic Nicolas Louis de La Caille visited Cape Town from 1751 to 1753. He undertook a careful examination of every square degree of the southern sky. This resulted in the first comprehensive sky survey ever made, in either hemisphere.

The Royal Observatory, Cape Town of Good Hope (today the South African Astronomical Observatory) was established in 1820. It became, and remained for 150 years, the most important source of star positions in the Southern Hemisphere sky. This was in terms of accuracy and the number of measurements made.

In the years that followed its foundation, the observatory’s laborious work led to important scientific discoveries.

Cape astronomers were responsible for, among other things, the first measurement of the distance to a star; the first photographic sky survey; and the accurate measurement of the distance to the sun. They were at the forefront of developments in stellar spectroscopy. This is the detailed analysis of a star’s light to find out its composition and movement towards or away from the sun. They also determined the shape of the Earth in the Southern Hemisphere and conducted the first accurate countrywide survey measurements of Southern Africa.

MEASURING STELLAR DISTANCES