Mzansi Afrika

From Johannesburg South Africa, a window on the world

Wednesday, May 26, 2004

On Matters Celestial

Transit of Venus
On Tuesday June 8, from sunrise until 1:30 pm, the planet Venus will be
seen as a small dark spot moving across the disk of the Sun. This
"Transit of Venus" is a rare event; no living person has seen one, as
the last occurred in 1882. Since the disk of the Sun is uncomfortably
bright to look at - and sustained staring may result in damage to the
retina - metallic foil, like that commonly used to pack tea bags, should
be held in front of the eye.

While the event will be visible to such suitably protected, but
otherwise naked, eyes, it will be better seen in images of the Sun
projected from telescopes. Weather permitting, a telescope will be set
up in front of the SA Museum, with planetarium staff in attendance.

In history, such transits of Venus, when observed from different
locations on Earth, were important scientific events used for
determining the scale of the Solar System (though nowadays this can be
found far more accurately by spacecraft). Many western nations
despatched expeditions to measure the timings of the transit of Venus,
the most famous being the first voyage of Captain James Cook to the
Pacific to observe the transit of 1761.

Transits of Venus occur in pairs. There will be another in 2012, but the
following pair only in 2117 and 2125. (From Iziko Museums Cape Town)


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