09 June 2012


Three days ago the planet Venus passed between the Earth and the Sun.  Such an event is called a transit, and the 2012 transit of Venus was one of the most-photographed celestial events in history.  According to NASA, "These [Venusian] transits occur in pairs eight years apart that are separated from each other by 105 or 121 years.  The last transit was in 2004 and the next will not happen until 2117."

In the image above (click to enlarge), Venus is the black sphere just inside the upper left arc, as it begins its transit.  Photos and videos like this give us a priceless perspective on the scale of objects and the distances between them.  Here's what I mean ~ we viewers on Earth are 93 million miles from the sun.  Venus, with 80 percent of Earth's mass, orbits at about 64 million miles from the Sun (and 29 million miles from Earth's orbit).  Yes, Venus is about two-thirds of the distance out from Sun to Earth.  Further, If you lined up 109 Earths in a row, they would equal the Sun's diameter.  Venus is even smaller than Earth.  It is the foreshortening of telephotography that creates the illusion that Venus is as large (relative to the Sun) as it appears to be in the image above.  The silhouette of Venus might be compared to that of the head of a pin, closer to the viewer than to the light bulb on the ceiling.

My Chicago friend Bill sent a link to what must surely be the definitive collection of videos of the Venus transit, provided by NASA, collected at various wavelengths of light.  Enjoy.

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