Transit Of Venus Approaching
May 21, 2012

Transit Of Venus Approaching

Lee Rannals for

In two more weeks, the Earth will get to view a spectacle that hasn't been seen in eight years, and will not be seen again until 2117.

Venus will pass across the face of the sun, producing a tiny silhouette, like a small freckle on a face.

The 7-hour transit will be observed on all seven continents on Tuesday, June 5, starting at 5:09 p.m. Central Time.

The transits of Venus first gained popularity back in the 18th century, a time when the solar system was still a big mystery to scientists.

The 2012 transit is the second of an 8-year pair, the first being back in June 2004.  No one alive during the transit eight-years ago had been around to have seen a Transit of Venus before.

Scientists and astronomers are even better prepared than they were eight years ago, and NASA's Solar Dynamics Observatory (SDO) is now in operation as well.

SDO, which launched back in February of 2010, will be able to provide Hubble-quality images of the event.

Astronomer Sir Edmund Halley was the first to realize that by observing transits from widely-spaced locations, it should be possible to triangulate the distance to Venus using the principles of parallax.

Bad weather and equipment prevented early observers from gathering the data they needed from Venus, so astronomers had to wait until the late 1800s for the invention of photography to take place to finally measure the size of the Solar System as Halley had suggested.

Now, with modern telescopes and camera equipment, astronomers will be able to capture images that seemed impossible back in the 1800s.  During the 2004 transit, one photographer caught the International Space Station transiting the sun alongside Venus.

The transit gives scientists a rare chance to study the atmosphere of Venus from Earth by using the planet's aureole.  As Venus makes contact with the edge of the Sun's disk, its aureole is outlined, showing a thin arc of light.

The aureole is caused by light refracted through the planet's atmosphere, and the brightness and thickness of it can give scientists more clues to the atmosphere temperature on the planet, as well as its cloud layers.

Other than factoring in weather, those wanting to get a glimpse of the Venus transit will need to be wearing some protective eyewear.  NASA says that #14 welder's glass is a good choice when wanting to observe the sun, without burning your retinas.

For photographers, the best way to snap a photo of the once-in-a-lifetime event is to pre-order a solar filter.  Solar filters are not commonly found at camera shops, so it´s best to ensure you have ordered one before June 5.