It's a phenomenon that takes place about 13 times in a century and won't happen again till 2032, but yesterday South Africans experienced this rare celestial event witnessing the Mercury transit across the sun.

 

Joining star gazers from across the globe, locals got out their telescopes or went online to see the transit, which last occurred on 9 May 2016.

 

The Department of Science and Innovation (DSI) was one of 20 sites countrywide that hosted viewing events yesterday. Other hosts included the South Africa Radio Astronomy Observatory, the Office of Astronomy for Development and the African Astronomical Society.

 

Charles Takalani, Junior Astronomy Policy Researcher at the DSI and Interim Administrative Officer at the African Astronomical Society, explained what transits are and why they occur.

 

"Transits in our solar system occur when Mercury or Venus passes directly in the field of view of Earth and the Sun. When Mercury came between the Sun and the Earth on Monday, the planet Mercury appeared as a small black dot moving across the face of the Sun (unlike a solar eclipse, when the Moon wholly or partially covers the Sun).

 

"As Mercury and Venus lie within the orbit of the Earth, they sometimes come exactly between us and the Sun, and can be seen crossing the face of the Sun for the duration of a few hours. These planets are much farther away from us than the Moon, and therefore appear to be much smaller in the sky than the Moon.  Because of the size of these planets relative to the Sun, a transit can only be seen by means of a telescope," said Takalani.

 

The transit could be observed only by projecting the image of the Sun through a small telescope. Observers were warned not to look at the Sun directly, even for a second, whether through a telescope or binoculars or with the naked eye, as this could cause permanent eye damage.  It is perfectly safe to look at the image projected onto a piece of paper.

 

The transit started at about 14:35 and lasted until sunset yesterday.

 

Takalani believes that it is important to raise awareness about such events in relation to planets in our solar system, as they are so rare and interesting for people to witness. It also creates an interest among young people who might be inspired to pursue careers in astronomy or other science-related fields.

 

The DSI invests heavily in astronomy and space-related programmes.