Venus makes transit across the Sun (Buthan Gragham)

 

The planet Venus passes across the sun, an astronomical event that won't be seen again until 2117. NBC's Mike Taibbi reports.

NASA via Reuters
An extreme ultraviolet picture of the sun from NASA's Solar Dynamics Observatory shows the planet Venus in transit, as well as dramatic swirls of solar activity.

Stan Honda / AFP - Getty Images
Venus can be seen at top right, beginning to cross the face of the sun, in a picture of the transit taken from Manhattan's West Side.

Andrew Burton / Getty Images
New Yorkers observe the last-in-a-lifetime transit of Venus from the High Line park.

NASA / SDO via Reuters
The planet Venus begins its six-hour-plus journey across the face of the sun, as seen in a close-up from NASA's Solar Dynamics Observatory.

Stan Honda / AFP - Getty Images
Clouds partially obscure the sun during the transit of Venus, as seen from Riverside Park on Manhattan's West Side.
The first scientific observation of a Venus transit took place in 1639, and there have five other transits to watch between then and now. Because of the orbital mechanics of our solar system, Venus can be seen crossing the sun's disk from Earth in pairs of occurrences separated by eight years. There are gaps of either 105.5 or 121.5 years between one pair and the next. One transit took place in 2004, and this is the second event in the pair. The next transit won't be seen until the year 2117 — thus, this is the last event of its kind that anyone alive today is likely to see.

Advertise | AdChoices

Scientifically speaking, the most important moments come as Venus crosses the edge of the sun's disk. That's when the sunlight refracted by Venus' atmosphere can be most easily detected — revealing the atmosphere's chemical signature. Astronomers eventually hope to use a similar technique to analyze the atmosphere of planets passing across alien suns, so this transit provides a good practice run for the technique. Even the Hubble Space Telescope is trying out the method, by checking the characteristics of the sunlight reflected by the moon during the transit.
If you want to see the transit yourself, make sure you do it safely — either by using appropriate protective eyewear or indirect observation methods such as a pinhole camera. There may be special events planned today by your local astronomy club, science center or observatory. Do not gaze at the sun without proper protection. Sunglasses won't do the trick, no matter how many you pile onto your face. Get the details from this safety guide.

Follow @CosmicLog

The safest and surest way to see the transit is on the Web. So check out this list of webcasts, and check back for updates as the transit continues.
·        NASA TV and NASA EDGE at Mauna Kea: The Hawaii show starts at 5:45 p.m. ET.
·        Exploratorium: The San Francisco science center's seasoned webcast team will be webcasting from Mauna Loa, Hawaii, starting at 6 p.m. ET.
·        Univ. of North Dakota SEMS (in Alaska): UND's Tim Young says the road show and the chat will start cooking from Alaska at 5:45 p.m. ET. "It is one of two locations in the U.S. that will see the whole transit," he told me via email. "The other is Hawaii, and other groups are webcasting from there."
·        Slooh Space Camera: Slooh starts its rock-solid webcast at 5:30 p.m. ET, featuring a dozen or more video feeds from Sweden, Norway, Australia, New Zealand, Hawaii, Arizona, New Mexico and other locales.
·        Universe Today: Live shots from around the world with commentary from Bad Astronomer Phil Plait, Pamela Gay and other celebrity guests.
·        Astronomers Without Borders: This show will be webcast from California's Mount Wilson Observatory.
·        Coca-Cola Space Science Center: Columbus State University's science center in Georgia is offering pictures from the home base in Columbus, Ga., as well as from Utah, Mongolia and Australia. The webcast gets started at 5:30 p.m. ET.
·        Mount Lemmon SkyCenter: The University of Arizona's astronomy center starts webcasting at 5 p.m. ET.
·        Appalachian State University: The view from one of the Rankin Science Observatory's 11-inch telescopes will be streamed from Boone, N.C., during a public viewing event.
·        Planet Hunters: The exoplanet-searchers will be carrying a webcast courtesy of theGLORIA Project, with live updates from Norway, Australia and Japan starting at 6:04 p.m. ET.
·        Bareket Observatory: The webcast from Israel starts at 10:33 p.m. ET, which is around sun-up at the site.
·        Kwasan Observatory: Watch a Japanese webcast from Kyoto.
·        Sky Watchers Association of North Bengal: SWAN's webcast from India gets under way at around 7:12 p.m. ET.
·        European Space Agency: ESA's Venus Transit Monitor will be transmitting images from Norway and Australia. Check out ESA's Transit of Venus blog for more.
·        And still more... NASA's Venus Transit website links to more webcasts, as doesSpace.com and Sky and Telescope.