Later today, our sister planet Venus will be inching its way across the face of the sun, providing a rare show to viewers around the world.
Transits of Venus have happened only 53 times in the last 4,000 years. They occur at most twice a century, with the most recent one in 2004. The next transit isn’t expected until Dec. 2117, making this the last chance to see the event in your lifetime.
Today’s event begins just after 3 p.m. PDT and will last nearly seven hours. It will be visible from all seven continents and is expected to attract millions of viewers. It’s not too late to get out and see the event live. You can find hundreds of places across the U.S. to watch the transit from, including universities, local museums, and amateur astronomer group parties. NASA has provided a great Google Maps mashup to search for events in your area.
Because of its extensive time length, the transit will overlap with sunset or sunrise in many areas. You can calculate which part of the transit you’ll see, but never fear: The full extent of the action will be visible live on the web no matter where you are.
Here, Wired Science has collected some of the best places on the internet to see this spectacular occurrence, and we’ll be hosting the best of these live feeds here on our site later today.
- NASA’s EDGE program will be hosting a feed from one of the best locations on Earth: on top of Mauna Kea in Hawaii, starting at 2:45 p.m. PDT. From here, the entire extent of the transit will be visible and the feed will include scientists and historians providing in-depth information at the transit.
- Astronomers Without Borders will have a live feed from Mount Wilson Observatory in California and will feature commentary from top experts in the history of astronomy.
- The Slooh Space Camera will track Venus from 10 different feeds using telescopes around the world beginning at 3 p.m. PDT. The consortium has lined up a distinguished speaker list including solar astronomer Lucie Green from the Mullard Space Science Laboratory, Bob Berman, monthly columnist for Astronomy Magazine, and John Spencer of the Southwest Research Institute. Slooh will also allow viewers to snap and share their own transit pictures from the feeds.
- The Exploratorium in San Francisco will have a live telescope feed with audio commentary every 30 minutes during the transit, starting at 3 p.m. PDT. The museum will also be creating a live sound composition from the video in real time.
- The National Solar Observatory will be updating its site with images from around the globe every minute, including experimental 3-D stereo images and films. The facility’s YouTube channel will also host movies of the final two hours of the event.
- The University of Barcelona in Spain will broadcast a live transit video from the Arctic Svalbard archipelago, in the northernmost part of Norway.
- Kwasan Observatory in Kyoto will have a live broadcast from a telescope in Japan.
- Perhaps the best seat in the house won’t be on Earth but rather flying high above it. Astronaut Don Pettit plans to photograph the transit from his perch on the International Space Station, marking the first time that humans have seen the transit from space. Pettit’s photos will be posted to a NASA Flickr account starting on June 5 around 3 p.m. PDT.
The transit of Venus is important not just for its rarity but also the historical weight it carries. Astronomers in the 17th century had used the laws of physics to calculate the relative distances between the planets, and learned, for instance, that Mars is about three times further from Venus than Earth is. But no one back then knew how to calculate the actual distance.
The transit of Venus gave astronomers in the preceding three centuries the opportunity to deduce the distance between Earth and Venus. Because of their separation, people on different sides of the Earth see Venus hit the sun’s limb at slightly different times. By combining this data with the known diameter of the Earth, and plugging it into some old-fashioned trigonometry equations, astronomers could calculate the distance between Earth and Venus. This, in turn, provided a yardstick to figuring out the size of the solar system in general.
During the 1700s in particular, European nations mounted expensive and often dangerous expeditions that sent scientists and explorers to the far reaches of our planet to get the data for these distance calculations. Captain James Cook made a famous sketch of his observation during the 1769 transit from Tahiti. More recently, researchers at Lick Observatory in California have strung together photographic plates from the 1882 transit to produce a movie recreating the event.
You can also participate in a modern-day experiment to recreate the heady days of scientific exploration. By downloading a free app, inputting your location as well as the exact time when Venus crosses and exits the sun’s limbs, you can help calculate the size of the solar system.
Even though astronomers have used modern robotic spacecraft to measure the size of the solar system with high accuracy, this year’s transit will help gather some interesting 21st century data. By observing how the sun’s light filters through Venus’ atmosphere, scientists will gain valuable information about its composition, map the carbon dioxide at infrared wavelengths, and study Venusian winds. Similar techniques could one day be used to probe the atmospheres of exoplanets around distant stars.
Image: Gestrgangleri/Wikimedia Commons