Venus in transit: The world will be watching

[ladysycamore]

Some of the best views of the June 8 Venus transit will be live on the Internet.
by Francis Reddy

Updated June 7, 2004
When clouds spoiled Guillaume Le Gentil's chance of viewing the 1769 transit of Venus, the French astronomer wrote that he was "more than two weeks in a singular dejection." In 1761, while outrunning British forces during the Seven Years' War, Le Gentil had lost his other opportunity to see this event.
If you're clouded out like Le Gentil on June 8 — well, there's always 2012. But observers with Internet access will have the best seats in the house.

Dozens of institutions will bring the transit to a browser near you, posting images and live video feeds to web sites across the Internet. The equipment ranges from modest to state-of-the-art. Research-grade instruments include the Swedish 1-meter Solar Telescope on the Canary Islands, and the trio of solar telescopes — in Australia, India, and the Canary Islands — of the National Solar Observatory's Global Oscillation Network Group (NSO/GONG). Both sites will be posting images and animations throughout the transit.

Even a few satellites will get in on the act. Right now, Venus can be seen drifting toward the Sun in one view from the Solar and Heliospheric Observatory (SOHO) satellite. SOHO monitors the Sun from a "halo orbit" around a point about 930,000 miles (1.5 million kilometers) closer to the Sun than Earth. The spacecraft is currently offset from a direct line between the pair, so from SOHO's viewpoint, Venus will track beneath the Sun instead of passing directly across it. Still, the spacecraft's instruments will detect the planet as it blocks diffuse ultraviolet light from the Sun's inner corona. Another consequence of the spacecraft's viewpoint is that the transit begins three hours after it starts at Earth. When the transit reaches its height for ground-based observers, around 4:20 A.M. EDT, it will just be starting for SOHO.

The Transition Region and Coronal Explorer (TRACE) satellite watches the Sun from Earth orbit, so its view of the transit will be similar to that seen by observers on the ground — with one exception. The reason scientists traveled the globe to view past transits was that Venus takes a slightly different track across the Sun when viewed from different locations on Earth. This shift is the parallax of Venus and can be used to determine the planet's distance. TRACE travels from pole to pole every orbit. From its perspective, the silhouette of Venus will "bounce" across the solar surface, regularly oscillating above and below the straight-line track Earth-based observers will see.

Both SOHO and TRACE scientists will use the black spot of Venus as a reference for improving their understanding of how stray light scatters within spacecraft instruments.

A table of sites providing live images of the transit is listed below. Because this event is both of historical significance and well publicized, expect Internet traffic to be heavy. Some sites may be unreachable at times.

And if you're clouded out and stuck in an Internet traffic jam? Well, there's always 2012.

Check out the site for Links to Venus transit images & webcasts:
http://www.astronomy.com/Content/Dyn...1/750amyns.asp