A rare celestial occurrence — the transit of Venus — will be visible to earthlings this evening. Next chance to see it: December 2117.
“The most simple explanation is that the planet Venus will pass between us and the sun, and it will appear as a dot on the surface of the sun that will move across the face of the sun,” said Walter Powell, a volunteer with the Stilabower Public Observatory in Lamar.
The observatory will be open for the event.
For astronomers throughout the ages, the transit of Venus has offered a scientific way to measure the size of our solar system by calculating the distance between the Earth and the sun.
The transit, although it happens only every century or so, actually occurs in pairs about eight years apart, with the first crossing for the current transit in 2004. Before that, the last transit of Venus took place in 1882.
Observers in the Midwest will see the transit of Venus starting at 5:04 p.m. today until sunset. The entire transit will last more than six hours.
“It’s the rarest of the rare,” Astronomy magazine’s Bob Berman said in a broadcast publicizing today’s live feed of the event on the space website Slooh. He and Slooh’s Patrick Paolucci predict that more than 1 million people will visit the site to witness what they are billing as “a worldwide event.”
“They only happen twice a century,” Berman said. “It happens, followed by 121 1/2 years before the next one; then eight; then 105; another eight years; 121 1/2 years; eight. That’s the sequence, and it repeats forever. Nobody alive now will see that next one. This is the last transit for everybody living today, so that makes it very rare and very special.”
In Lamar, Powell will open the observatory at Fifth and Maple streets from about 5 to 8:30 p.m. to give area residents a place to view the transit. Although a telescope is not necessary, the transit is best seen when it is magnified.
Powell said he hopes viewers in Lamar will be able to use the observatory’s 14-inch telescope, which he plans to outfit with a solar filter.
“Through a telescope without a filter, it would instantly fry your eye,” he said. “But if our solar filter isn’t viable — as we haven’t used it in a while and don’t yet know its condition — we can still set up a projection apparatus to view it instead.”
For those without access to a telescope, viewing from a yard is fine, Powell said, but people should “never look at it with the naked eye” or with standard sunglasses. Instead, he recommends making a pinhole projector using a thin piece of cardboard opaque enough to block the sunlight, then projecting the image onto a sheet of paper beneath it.
Experts suggest that one widely available filter for safe solar viewing is No. 14 welder’s glass. It is imperative that the welding hood houses a No. 14 or darker filter.
A variety of viewing methods also are described in detail at http://venustransit.nasa.gov, where NASA will offer a live webcast of the event that will last the length of the transit. The footage will stream live from the summit of Mauna Kea, Hawaii, with accompanying commentary from experts. Times are subject to change, but the webcast is scheduled to begin at 4:45 p.m. Joplin time.
Another option is to view the transit from your armchair via www.slooh.com.
“It’s the biggie on the calendar,” said Slooh’s Paolucci.
“Historically, with many observations made through the centuries, we’re able to pin down the true scale of the solar system, the true distance to the sun, so it’s of great scientific interest for many many centuries,” Berman said. “Now, it’s a little less crucial scientifically, but it’s still plenty interesting as a spectacle.”
VENUS IS EARTH’S nearest neighbor. Only two celestial objects, other than the Earth’s moon, eclipse the sun: Mercury, which is too small to be seen with the naked eye, and Venus.