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Rare Venus Transit Won't Happen Again for 105 Years
2004 Venus transit

NASA's TRACE satellite captured this image of Venus crossing the face of the sun as seen from Earth orbit. Credit: NASA

On June 5, something will happen in the heavens that won't again for more than a hundred years. The planet Venus will pass between Earth and the sun, and the transit will be visible to the naked eye.

Astronomers around the world are gearing up for the event. NASA plans to image it with the Hubble Space Telescope and air a live webcast from a mountaintop in Hawaii.

And NASA's sun-watching Solar Dynamics Observatory (SDO) satellite will have an unparalleled orbital view of the seven-hour transit. A team of SDO scientists is heading to Alaska to watch.

Alaska and Hawaii are the only U.S. states where the whole transit can be viewed. The event won't be repeated until 2117.

The transit here will be visible starting at 6:09 p.m. and ends 8:22 p.m. with sunset in Hampton Roads, Virginia.

Like an eclipse

"It will be exactly like a sun eclipse, but here, it is Venus," said Guillaume Gronoff, a scientist at NASA's Langley Research in Hampton, Va., and a member of the Hubble team.

Safety First!
Safe viewing of the Venus transit is essential to prevent your eyes from being seared by the sun. Cheap sunglasses won't work. You'll need welder's glass -- No. 14 - or special viewing glasses that might be sold in stores specifically for this event, and filters if you use a telescope, or a projector. Go to this site for more information:


› Venus Transit Site
› Webcast Info
› Hubble Transit Background

As Venus passes in front of the sun, it will appear "quite small-looking … a small dot on the surface," he said.

Venus transits occur in pairs eight years apart and take place less than once every century. The last one occurred June 8, 2004 and was watched by millions of people around the world. Fifty-three transits of Venus across the sun have happened in the last 4,000 years.

The 2012 event will be webcast by Langley's NASA EDGE vodcast in partnership with the University of Hawaii Institute for Astronomy.

"Leveraging our partnership with the University of Hawaii will let us show real-time images of the transit, for the duration of the event, in various wavelengths of light," said Chris Giersch, the show's host.

Mirror, mirror on the moon

Meanwhile the Hubble Space Telescope will use mirror magic to capture images. Hubble cannot look at the sun directly, so astronomers will point it at Earth's moon, using the surface as a mirror to obtain images.

A similar technique is used to sample the atmospheres of "exoplanets" outside our solar system passing in front of their stars. Astronomers already know the chemical makeup of Venus's atmosphere, and that it does not show signs of life on the planet.

But the Venus transit will be used to test whether this technique will have a chance of detecting the fingerprints of an Earth-like planet outside our solar system that similarly transits its own star.

"One of the big questions about the exoplanets is, what is the composition of the atmosphere? The only way we have to detect that is to study the transits," said Gronoff, who studies the upper atmospheres of planets. "The transit of Venus is perfect as a benchmark for the exoplanets and, we will see if what we discover is in agreement about what we know of Venus."

Locally, the Virginia Peninsula Astronomy/Stargazers plans a June 5 viewing at Huntington Beach on the James River in Newport News, said Lawrence Taylor, a club member who works at NASA Langley.

Michael Finneran
NASA Langley Research Center