Transit of Venus Across the Sun 2012: Latest News news tech spaceflight science & astronomy search for life skywatching entertainment video Transit of Venus Across the Sun 2012: Latest News Get the latest news and tips for the rare Venus transit across the sun on June 6, 2012. The next one is in 2117! Filter by Type Rare Mercury Transit Thrills Skywatchers Around the World (Photos) May 10, 2016 | Article Mercury popped onto the solar disc at 7:16 a.m. EDT (1116 GMT) Monday and departed more than 7 hours later, completing the first "Mercury transit" since 2006. Observers around the world were ready, and many captured stunning photos. Mercury Transit: The History and Science of This Rare Celestial Event May 07, 2016 | Article On Monday, May 9, Mercury will appear to pass across the disk of the sun as seen from Earth. This event — which astronomers call a transit — helped early astronomers measure distances in the solar system. Mercury Transit of the Sun: Why Is It So Rare?

May 06, 2016 | Article Mercury transits occur just 13 times per century, on average. They're so rare because the innermost planet's orbit is inclined by about 7 degrees compared to that of Earth, so Mercury, the sun and our home planet just don't line up all that often. Are You Ready for the Transit of Mercury? Rare Event Occurs in May April 06, 2016 | Article Start preparing now for one of the major astronomical events of 2016: On May 9, Mercury will pass across the face of the sun. Venus Shines Near Saturn in Dazzling Display This Weekend January 06, 2016 | Article On Friday (Jan. 8), the planet Venus will appear to pass close by Saturn, making this a rare opportunity to see two planets at the same time in a telescope's narrow field of view. Venus Shining at Its Best in the Night Sky June 06, 2015 | Article If you've been watching the sky in the early evening lately, you can't have missed seeing the planet Venus in the west and now this planet is putting on brilliant show in the night sky.

Venus, Jupiter and Saturn (Oh, My!) The Brightest Planets of June June 05, 2015 | Article With the northern summer just a few weeks away, the month of June is bringing a delight of planets in the night sky for stargazers to enjoy, but only if weather permits and you know when and where to look. Brilliant Venus and Moon Shine Together Tonight: How to See It April 21, 2015 | Article This evening will be another one of those special occasions when the two brightest objects in the night sky — the moon and a Venus — will get together and, weather permitting, will attract a lot of attention. Venus Points the Way to Mercury in Night Sky This Week January 08, 2015 | Article The hard-to-spot planet Mercury can be found near Venus just after sunset this week, offering a great chance to see the closest planet to sun. Here's how to see Mercury and Venus together in January's night sky.

Planet Venus to Dazzle Stargazers in 2015 Night Sky January 02, 2015 | Article Currently hovering very low in the southwest twilight sky near the setting sun these evenings is the most brilliant of the planets: Venus. And in the New Year, this planet will truly shine. Transit of Venus 2012—Sun Show Will Be Last for a Century Transit of Venus 2012—Sun Show Will Be Last for a Century How to see rare planetary lineup that may unlock puzzles of alien worlds. View Images Venus glides across the sun's face during its previous transit, seen from Flagler Beach Pier in Florida. Photograph by Jim Tiller, Daytona Beach News-Journal/AP Early this week sky-watchers around the world will be able to witness a transit of Venus —a celestial event that won't be seen again for more than a century. Related Content Finding Clarity in the Stars Visible either Tuesday or Wednesday, depending on where you live, the transit will offer astronomers a chance to refine our understanding of Venus as well as to tweak models for searching for planets around other stars. ( Pictures: See what the Venus transit will look like.

) Transits happen when a planet crosses between Earth and the sun. Only Mercury and Venus, which are closer to the sun than our planet, can undergo this unusual alignment. With its relatively tight orbit, Mercury circles the sun fast enough that we see the innermost planet transit every 13 to 14 years. But transits of Venus are exceedingly rare, due to that world's tilted orbit: After the 2012 Venus transit, we won't see another until 2117. During the upcoming transit, Venus will look like a black dot gliding across the face of the sun over the course of about six hours. "Venus's diameter will appear only about a 30th the diameter of the sun, so it will be ... like a pea in front of a watermelon," said Jay Pasachoff , an astronomer at Williams College in Massachusetts. (Read a Q&A with Pasachoff about Venus transits .) "The effect won't be visually impressive, but that black dot against the sun is a remarkable thing to see." Watch a live broadcast of the 2012 transit of Venus.

The entire transit of Venus will be visible from Hawaii, Alaska, New Zealand, Japan, the Philippines, most of Australia, and parts of eastern Asia. Countries in the Western Hemisphere will see the transit on Tuesday, while those in the Eastern Hemisphere will see it on Wednesday. (See a visibility map for the transit of Venus .) Viewers in North America will see Venus start to cross the sun in the late afternoon on Tuesday, but the sun will set with the planet still in transit. Observers in Europe, Africa, and western Australia, meanwhile, will see the sun rise Wednesday morning with Venus already on its face. Venus on the Edge The 2012 transit of Venus will be visible even to the naked eye—although astronomers caution that people should never look directly at the sun without proper protection. To watch safely, observers should always use special "eclipse glasses" or telescopes equipped with solar filters. Perhaps the safest way to watch the transit of Venus is to make a pinhole camera, said Pasachoff, who is also a National Geographic Society Committee for Research and Exploration grantee .

(National Geographic News is a division of the Society.) To do so, cut a hole about a quarter-inch (0.6-centimeter) wide in a piece of cardboard paper, and use the hole to project an image of the sun onto a flat surface, such as a wall or sidewalk. During the transit, the leading edge of Venus's silhouette will first touch the upper left side of the sun's disk. In less than half an hour, Venus's opposite edge will touch the same point of the solar limb. At this stage, the planet's circular shape will appear to be distorted into a teardrop for a few minutes—something astronomers call the black drop effect. "It's believed that this is an effect of blurring by Earth's atmosphere, combined with the apparent slight darkening of the sun's visible surface near its edges," said Ben Burress, a staff astronomer at the Chabot Space and Science Center in Oakland, California. Depending on local sky quality, the altitude of the observer, and the size of the telescope, observers may also glimpse Venus's atmosphere during the transit, Burress said.

(Related: "Venus Spinning Slower Than Thought—Scientists Stumped." ) "A bright rim around the edge of Venus against the background of space may be visible just as Venus is entering or leaving the solar disk," he said. "This is caused by sunlight refracting"—or bending—"in the dense upper atmosphere of Venus." Measuring the Solar System Transits of Venus are so rare because the planet's orbit is tilted just over three degrees from the plane of the solar system. This means that most of the time Venus passes above or below the sun's disk, as seen from Earth. On average, we see four transits of Venus within 243 years. The events happen in pairs spaced eight years apart, and they alternate whether Venus crosses the top or the bottom of the solar disk, Williams' Pasachoff said. This year, for instance, the planet will transit the top of the sun. Astronomers first used telescopes to observe a transit of Venus in 1639.

But it wasn't until 1769 that dozens of scientists scattered across the globe to make detailed measurements of the event, including the famous voyage of British lieutenant James Cook, who had astronomers collecting transit data from the island of Tahiti during his South Pacific expedition. Observations from different locations on Earth allowed scientists to not only triangulate the true size of the sun but also to more accurately determine the distance between the sun and Earth. "Prior to that, the estimates of those scales were mostly educated guesswork," Chabot's Burress said. Based on the 18th-century transit, astronomers calculated that the sun is 95 million miles (153 million kilometers) away—only slightly off from the true Earth-sun distance of 93 million miles (150 million kilometers).

"Since we already knew the relative spacing between the orbits of all the planets, once we determined the Earth-sun distance, in one fell swoop we were able to calculate the distances to all the other planets." Venus Transit a Key to Planetary Puzzles Today, 21st-century astronomers hope to use the 2012 transit of Venus to collect data on the planet's atmosphere and compare their findings to measurements from the European Space Agency's Venus Express orbiter . The orbiter has returned information on intriguing weather patterns in Venus's dense atmosphere, but at close range the craft can see only one region at a time. Venus Crosses the Sun for Last Time Until 2117, Skywatchers Rejoice Venus Crosses the Sun for Last Time Until 2117, Skywatchers Rejoice By Tariq Malik, Space.com Managing Editor | June 6, 2012 01:13am ET MORE This view of the historic transit of Venus of June 5, 2012, shows the path of Venus at different stages of the event as seen by NASA's Solar Dynamics Observatory spacecraft.

Credit: NASA/SDO, HMI NEW YORK – It's something no one alive today will likely ever see again: The planet Venus crossing the sun — a small, black dot moving across the fiery face of our nearest star. The transit of Venus across the sun is one of the rarest celestial sights visible from Earth, one that wowed scientists and amateur observers around the world Tuesday (June 5). The event, arguably the most anticipated skywatching display of the year, marked the last time Venus will cross the sun (as seen from Earth) for 105 years. Only seven Venus transits have been witnessed since the invention of the telescope 400 years ago, and you'd have a long wait for the next one. It won't happen again until Dec. 11, 2117. To celebrate the last transit of Venus in the 21st century, astronomers and skywatchers came together in many sites around the world. In the United States, NASA beamed images of the transit from an observatory atop Mauna Kea in Hawaii (just one of many webcasts from many countries) and welcomed the public to its various space centers, including the Ames Research Center in Moffett Field, Calif.

[ Amazing Venus Transit 2012 Pictures ] "It's truly inspiring to see so many faces here to share this moment with us," Natalie Batalha, the deputy science team leader of NASA's planet-hunting Kepler space telescope, told visitors at Ames. "It's going to give you, I hope, a profound feeling of the grandeur of our own solar system. You're going to see Venus in person, with a spotlight shining on her." Tuesday's transit began just after 6 p.m. EDT (2200 GMT) and lasted about six hours and 40 minutes. It was visible across North America, Europe, Asia and eastern Africa. Because of the International Date Line, some parts of the world saw the transit on June 6. Credit: NASA / SDO A rare celestial sight Venus transits occur when Venus reaches a point in its orbit that brings the planet directly between the Earth and the sun. Since the tilt of Venus' orbit isn't exactly the same as that of Earth, the events are rare, occurring just four times every 243 years. Skywatcher Tim McCord caught the Venus transit on June 5, 2012, in Entiat, WA.

Credit: Tim McCord The transits occur in pairs eight years apart. Since the June 5 transit followed a previous Venus sun crossing in 2004, this is the last one of the current cycle. Venus and Mercury are the only planets that can be seen crossing the sun from Earth since their orbits are between our planet and the sun. The next Mercury transit will be on May 9, 2016. Despite the extreme rarity of Venus transits , they hold a wealth of information about Venus, the sun and our solar system. Since the first documented observation of a Venus transit in 1639, astronomers have used the events to measure the size of the solar system, the intricacies of Venus' atmosphere, the width of the sun and more. [ Venus Crosses Sun's Hellfire in 2012 Transit (Video) ] In fact, NASA and other space agencies trained a fleet of satellites to watch the Venus transit in unprecedented detail. NASA's powerful Solar Dynamics Observatory captured spectacular photos and movies of the entire transit.

Astronomers and skywatchers were eagerly looking forward to seeing the so-called " Black Drop Effect ," an optical illusion that occurs when just after Venus moves on to the sun's disk and just before it exits. During the illusion, the black disk of Venus appears to be connected to the edge of the sun due to a trick of optics, NASA officials said. This image is from NASA Astronaut Don Petttit shot from onboard the International Space Station on June 5, 2012. Credit: NASA Even astronauts in space caught Venus transit fever. NASA astronaut Don Pettit photographed the Venus transit from the observation deck of the International Space Station. He is the first person ever to photograph the transit from space and has been a prolific photographer of Earth and space during his months-long mission aboard the space station. "For scientific purposes today, the transit of Venus is more of an educational opportunity to look at celestial events and learn and be delighted about how our solar systems, and the dynamics of the planets, operate," Pettit said in a video before the transit.

Venus-watching in the Big Apple Here in New York City, hundreds of skywatchers flocked to Manhattan's west side where the Amateur Astronomers Association of New York set up two separate observing posts to catch the historic Venus transit. Clouds and occasional rain put a damper on the viewing, but for brief moments the skies parted allowing for amazing views. Megan McDavid, of Brooklyn, said she came out to see the transit because: "It's a once-in-a-lifetime opportunity. This is my last chance, how could you miss it?" She admitted that the small dot of Venus was "hard to see" without telescope magnification, but said, "I feel lucky we got a few breaks in the clouds and I got a chance to see it." A large crowd turned out to view the transit of Venus at the American Museum of Natural History in New York, where astronomer Steve Beyer explained what the crowd was going to see. Credit: Denise Chow/SPACE.com Elsewhere in Manhattan, nearly 600 people packed the American Museum of Natural History to watch Venus cross the sun. The museum carried NASA's webcast from Mauna Kea live, with the crowd cheering as the event began.

"We watched a dot move across the screen and it was awesome," said skywatching enthusiast Kip Daly, 16, when asked what he'd tell his future children about the transit. Planet Venus is often likened to Earth but with a runaway greenhouse problem. The 2nd planet from the sun is hot shrouded with deadly clouds. Those are hints. Now test your knowledge of Venus facts. Venus transit 2012: Planet Venus moves across the sun | WJLA Circa Venus transit 2012: Planet Venus moves across the sun The transit will appear as a small black dot against the sun. Viewers risk blindness if they attempt to look at it directly. (Photo: Colin.jagoe/flickr) AA Amateurs and experts alike took time out of their daily routine to gaze up at the sky Tuesday. In a rare appearance, the planet Venus passed in front of the sun. It won't do it again for nearly 100 years. Several watch parties were held across the D.C. region to view the amazing event.

"We're in a straight line, Venus is directly between the sun and us, so we see it as the dark shadow showing up right now," Jim Zimbelman, a planetary geologist, said as onlookers watched. Hundreds of years ago, astronomers used events like this to figure out the size of the solar system, Today, they collected data that will help them detect planet hundreds of light years away. Zimbelman explains, "The hope is that we'll improve our ability to detect atmospheres of planets around other stars. I think that's pretty exciting!" The transit was happening during a 6-hour, 40-minute span that began just after 6 p.m. EDT in the United States. What observers could see and for how long depended on their region's exposure to the sun during that exact window of time, and the weather. Those in most areas of North and Central America saw the start of the transit until sunset, while those in western Asia, the eastern half of Africa and most of Europe could catch the transit's end once the sun came up. Hawaii, Alaska, eastern Australia and eastern Asia including Japan, North and South Korea and eastern China get the whole show since the entire transit happens during daylight in those regions.

While astronomers used the latest technology to document the transit, American astronaut Don Pettit aboard the International Space Station was planning to take photos of the event and post them online. Meanwhile, terrestrial stargazers were warned to only look at the celestial event with a properly filtered telescope or cardboard eclipse glasses. If the sun is viewed directly, permanent eye damage could result. In Los Angeles, throngs jammed Mount Hollywood where the Griffith Observatory rolled out the red carpet for Venus. The last time the city witnessed a Venus transit was 130 years ago in 1882. A 2004 transit was not visible from the western U.S. Telescopes with special filters were set up next to the lawn and people took turns peering at the sun before and during the transit. Astronomers and volunteers lectured about the rarity of a Venus pass to anyone who would listen. Minutes before Venus first touched the outer edge of the sun, Sousa's "Transit Of Venus March" blared through. The crowd turned their attention skyward. Jamie Jetton took the day off from work to bring her two nephews, 6 and 11, visiting from Arizona to the observatory.

Sporting eclipse glasses, it took a little while before they spotted Venus. "I'm still having fun. It's an experience. It's something we'll talk about for the rest of our lives," she said. Bo Tan, a 32-year-old software engineer took a half day off from work and went with his co-workers to the observatory. He admitted he wasn't an astronomy buff but could not miss this opportunity. He pointed his eclipse glasses at the sun and steadied his Nikon camera behind it to snap pictures. "It makes you feel like a small speck in the universe," he said. In Mexico, at least 100 people lined up two hours early to view the event through telescopes or one of the 150 special viewing glasses on hand, officials said. Observation points were also set up at a dozen locations. Venus, which is extremely hot, is one of Earth's two neighbors and is so close in size to our planet that scientists at times call them near-twins. During the transit, it will appear as a small dot. This will be the seventh transit visible since German astronomer Johannes Kepler first predicted the phenomenon in the 17th century.

Because of the shape and speed of Venus' orbit around the sun and its relationship to Earth's annual trip, transits occur in pairs separated by more than a century. It's nowhere near as dramatic and awe-inspiring as a total solar eclipse, which sweeps a shadow across the Earth, but there will be six more of those this decade. In Hawaii, hundreds of tourists and locals passed through an area of Waikiki Beach where the University of Hawaii set up eight telescopes and two large screens showing webcasts of the transit as seen from telescopes at volcanoes on other Hawaiian islands. But minutes after Venus crossed into the sun's path, clouds rolled overhead and blocked the direct view. "It's always the challenge of being in Hawaii - are you going to be able to see through the clouds," said Greg Mansker, 49, of Pearl City, as he stood in line at a telescope. The intermittent clouds didn't stop people from looking up through filters, but it did drive some to crowd the screens instead. Jenny Kim, 39, of Honolulu, said she told her 11-year-old son the planet's crossing would be the only time he'd get to see the transit in person.

"I don't know what the future will be, so I think this will be good for him," Kim said as she snapped photos of the webcast with her smartphone. Astronomers also planned viewings at Pearl Harbor and Ko Olina. Some observers at the University of Alaska, Anchorage gathered on a campus rooftop, peering at Venus through special filtered glasses and telescopes. "It's not really spectacular when you're looking at it," Kellen Tyrrell, 13, said. "It's just the fact that I'm here seeing it. It's just so cool that I get to experience it." NASA planned a watch party at its Goddard Visitor Center in Maryland with solar telescopes, "Hubble-quality" images from its Solar Dynamics Observatory Mission and expert commentary and presentations. Most people don't tend to gaze at the sun for long periods of time because it's painful and people instinctively look away. But there's the temptation to stare at it during sky shows like solar eclipses or transits of Venus. The eye has a lens and if you stare at the sun, it concentrates sunlight on the retina and can burn a hole through it.

It's similar to when you hold a magnifying glass under the blazing sun and light a piece of paper on fire. It can take several hours for people to notice problems with their eyes but, by that time, the damage is done and, in some cases, irreversible. During the 1970 solar eclipse visible from the eastern U.S., 145 burns of the retina were reported, according to the American Academy of Ophthalmology. Experts from Hong Kong's Space Museum and local astronomical groups were organizing a viewing Wednesday outside the museum's building on the Kowloon waterfront overlooking the southern Chinese city's famed Victoria Harbor. On the East Coast of the United States, amateur astronomer Vince Sempronio was at a viewing hosted by Montgomery College in Takoma Park, Md., but clouds there - as in many other places - left many to crowd around a laptop to watch the NASA webcast instead of the Venus move across the sun. "I was here at the same spot eight years ago when we had the last transit and I was able to show people, using my telescope then. So I'm not too disappointed," Sempronio said.

"If modern science and medicine helps, maybe I'll be around in a hundred and five years to see the next one. But I'm not crossing my fingers." The Associated Press contributed to this report. NASA - Planetary Transits Page Planetary Transits Across the Sun Transit of Mercury on 1973 Nov 10. The transit or passage of a planet across the disk of the Sun may be thought of as a special kind of eclipse. As seen from Earth, only transits of the inner planets Mercury and Venus are possible. Planetary transits are far more rare than eclipses of the Sun by the Moon. On the average, there are 13 transits of Mercury each century. In comparison, transits of Venus usually occur in pairs with eight years separating the two events. However, more than a century elapses between each transit pair. The first transit ever observed was of the planet Mercury in 1631 by the French astronomer Gassendi. A transit of Venus occurred just one month later but Gassendi's attempt to observe it failed because the transit was not visible from Europe. In 1639, Jerimiah Horrocks and William Crabtree became the first to witness a transit of Venus.

At the present time, all transits of Mercury fall within several days of May 08 and November 10. Since Mercury's orbit is inclined seven degrees to Earth's, it intersects the ecliptic at two points or nodes which cross the Sun each year on those dates. If Mercury passes through inferior conjunction at that time, a transit will occur. During November transits, Mercury is near perihelion and exhibits a disk only 10 arc-seconds in diameter. By comparison, the planet is near aphelion during May transits and appears 12 arc-seconds across. However, the probability of a May transit is smaller by a factor of almost two. Mercury's slower orbital motion at aphelion makes it less likely to cross the node during the critical period. November transits recur at intervals of 7, 13, or 33 years while May transits recur only over the latter two intervals. The following table lists all transits of Mercury from 1901 through 2050. For a more complete and detaled list, see Seven Century Catalog of Mercury Transits: 1600 CE to 2300 CE .

Transits of Mercury: 1901-2050 Date Universal Separation* Time (Sun and Mercury) 1907 Nov 14 12:06 759" 1914 Nov 07 12:02 631" 1924 May 08 01:41 85" 1927 Nov 10 05:44 129" 1937 May 11 09:00 955" 1940 Nov 11 23:20 368" 1953 Nov 14 16:54 862" 1957 May 06 01:14 907" 1960 Nov 07 16:53 528" 1970 May 09 08:16 114" 1973 Nov 10 10:32 26" 1986 Nov 13 04

:07 471" 1993 Nov 06 03:57 927" 1999 Nov 15 21:41 963" (graze) 2003 May 07 07:52 708" 2006 Nov 08 21:41 423" 2016 May 09 14:57 319" 2019 Nov 11 15:20 76" 2032 Nov 13 08:54 572" 2039 Nov 07 08:46 822" 2049 May 07 14:24 512" * distance (arc-seconds) between the centers of the Sun and Mercury To determine whether a transit of Mercury is visible from a specific geographic location, it is simply a matter of calculating the Sun's altitude and azimuth during each phase of the transit using information tabulated in the Seven Century Catalog of Mercury Transit .

For the relevant equations and a sample calculation , see Transit Visibility . This web page also has links to several Excel files which perform the calculations automatically when the user inputs the latitude and longitude of any location. In 1716, Edmond Halley published a paper describing exactly how transits could be used to measure the Sun's distance, thereby establishing the absolute scale of the solar system from Kepler's third law. Unfortunately, his method proved somewhat impractical since contact timings of the required accuracy are difficult to make. Nevertheless, the 1761 and 1769 expeditions to observe the transits of Venus gave astronomers their first good value for the Sun's distance. Photograph of the Transit of Venus on 1882 Dec 06. Taken by students at Vassar College (Sky & Telescope Feb. 1961). Because Venus's orbit is considerably larger than Mercury's orbit, transits of Venus are much rarer. Indeed, only six such events have occurred since the invention of the telescope (1631,1639, 1761,1769, 1874 and 1882).

Transits of Venus are only possible during early December and June when Venus's orbital nodes pass across the Sun. Transits of Venus show a clear pattern of recurrence at intervals of 8, 121.5, 8 and 105.5 years. The following table lists all transits of Venus during the 800 year period from 1601 through 2400. For a more complete and detaled list, see Six Millennium Catalog of Venus Transits: 2000 BCE to 4000 CE .

Transits of Venus: 1601-2400 Date Universal Separation Time (Sun and Venus) 1631 Dec 07 05:19 940" 1639 Dec 04 18:25 522" 1761 Jun 06 05:19 573" 1769 Jun 03 22:25 608" 1874 Dec 09 04:05 832" 1882 Dec 06 17:06 634" 2004 Jun 08 08:19 627" 2012 Jun 06 01:28 553" 2117 Dec 11 02:48 724" 2125 Dec 08 16:01 733" 2247 Jun 11 11:30 693" 2255 Jun 09 0

4:36 492" 2360 Dec 13 01:40 628" 2368 Dec 10 14:43 835" To determine whether a transit of Venus is visible from a specific geographic location, it is simply a matter of calculating the Sun's altitude and azimuth during each phase of the transit using information tabulated in the Six Millennium Catalog of Venus Transits .

For the relevant equations and a sample calculation , see Transit Visibility . This web page also has links to several Excel files which perform the calculations automatically when the user inputs the latitude and longitude of any location. The 2004 transit of Venus was visible from Europe, Africa and Asia. However, the final stages of the event were also visible from the eastern USA and Canada. Complete details can be found at 2004 Transit of Venus . The 2012 transit of Venus will be visible from North America, the Pacific, Asia, Australia, eastern Europe, and eastern Africa. Details can be found at 2012 Transit of Venus . Transit Predictions Transit of Venus – as it happened | Science | theguardian.com Blog home Transit of Venus – as it happened Join us as we track the final time that Venus will cross the sun in our lifetime with tidbits of history, snatches of science and scraps of literature to enhance the viewing • All times ET MORE: Highlights from this live blog Handout image courtesy of NASA shows the planet Venus at the start of its transit of the Sun, June 5, 2012.

Photograph: Nasa/Reuters 4.15pm: Hello and welcome to our live blog coverage of the 2012 transit of Venus. We are unduly excited to bring you live updates of the action overhead. As the evening progresses we'll add tidbits of history, snatches of science and scraps of literature in an effort to enhance enjoyment of and do justice to what we are about to see: the last transit of our lifetimes. Let's start with the basics: • What's the transit of Venus? It's Venus crossing the sun, and it is one of the most celebrated spectacles in all of astronomy. That's because a pair of such transits in the late 18th-century allowed astronomers to calculate for the first time how big the solar system is. Also it looks cool. • Can I watch it? Yes. Local viewing times are here . In the eastern US it begins at 6.03pm and ends at 12.51am. Astute readers will note that viewing in the east will necessarily be cut short; the sun is not visible at midnight. True, but thanks to Nasa, you can watch the entire breathtaking transit here .

Nasa's live coverage begins at 5.45pm ET. • Do I need special eye protection to view the transit? If you're old enough to read this live blog (which after dark will feature 19th-century nudes of the goddess Venus), you're old enough to know that the answer to that question is yes. To stare into the sun is to risk grave eye damage without the guarantee of sympathy. Nasa has a guide to safe solar viewing here . • A dot on the sun. What's the big deal? Three quick answers: the transit of Venus set in motion one of the greatest quests of all time, a race across the seas to measure the heavens; the transit produced one of the greatest breakthroughs in the history of science; and it won't happen again till 2117, 105 years from now. (The last one occurred in 2004; there were none in all the 20th-century.) Join us! 4.45pm: Transits of Venus occur in pairs. The pairs are separated by alternating chunks of either 121.5 or 105.5 years. The two transits making up a pair are separated by eight years.

The current transit is the second of a pair; its counterpart occurred in June 2004. Guardian science correspondent Ian Sample has assembled a list of questions about the transit, asked and answered. We're not calling them FAQs; with hundred-year chunks of downtime, we just don't think the word "frequently" applies. Here's a bit from Sample's Q&A : What have scientists used the transit for? In the 18th century astronomers set out to far-flung corners of the globe to time the transit of Venus. Combined, their results gave them the first accurate measurement of the distance between the Earth and the sun, a figure they calculated to be between 93 million and 97 million miles (172-180 million kilometres). Today, the accepted distance is 93 million miles. The result allowed astronomers to calculate the size of the solar system. Read the whole Q&A here . Nasa has produced a video explaining the transit of Venus, embedded below, with this to say about the historical importance of the transit: "Astronomer Sir Edmond Halley realized that by observing transits from widely spaced locations on Earth, it should be possible to triangulate the distance to Venus.

The idea galvanized scientists, who set off on expeditions around the world to view a pair of transits in the 1760s. The great explorer James Cook himself was dispatched to observe one from Tahiti, a place as alien to 18th-century Europeans as moon or Mars." 5.05pm: Note to our readers: Scientists believe that the planet Venus has not been live blogged on any of its previous transits. It is unknown whether other activity on Venus or by Venus has previously been subject to blogging elsewhere in the universe not on Earth. Suffice it to say that until we hear differently, and possibly even after we hear differently, we are going to claim the mantle of live blogger pioneers in the realm of cosmic phenomena. Both Capt. James Cook and the botanist Joseph Banks kept extensive diaries on their 1769 voyage to Tahiti to view the transit, but they forgot to upload them upon their return to London. 5.20pm: About 43 minutes to go now until the transit begins. Time to introduce a towering figure in astronomy in general and in the history of observation of the transit of Venus in particular: Edmond Halley.

Halley is best known to the layperson for having predicted the return of the comet that bears his name. Halley's comet decorates the heavens every 75-76 years (the last time was February 1986; the time before that was April 1910; the next time is July 2061). Edmond Halley, the English astronomer and geophysicist. Photograph: Guardian The historian Andrea Wulf, author of the lovely book "Chasing Venus: The Race to Measure the Heavens," spoke to the Guardian about Halley's role in launching the world expeditions to view the transit – after his death: IN 1716, almost 50 years before the 1761 transit happens, Halley sits down and he writes an essay, in Latin, because that's the international language of science.. ... and in this essay, he says, 'This is what we have to do. In 1761, you all have to work together.' And he very much emphasizes that all the different European nations should make use of their colonial possessions. The English would send someone out to India, the Dutch to Jakarta.

He's using the trading empires to have this idea. He knows that this can only happen if everybody works together. That's why he writes it in Latin. And what's so visionary about it is he knows that he's not going to see this, unless he would be 104, which he knows he's not going to be. So it's like a call of action for a future generation. Here's the webcast. 5.40pm: Andrea Wulf's history of the chase to observe the 18th century transits of Venus begins with an epigraph from Jeremiah Horrocks, the young amateur astronomer who, with his partner William Crabtree, was the only person to see the 1639 transit. The English astronomer Jeremiah Horrocks becoming the first person to witness a transit of Venus in 1639. Horrocks writes with uncommon eloquence – and a malaise that seems quaint for a scientist – about the transit.

"The planet Venus drawn from her seclusion, modesly delineating on the sun, without disguise, her real magnitude, whilst her disc, at other times SO lovely, is here obscured in melancholy gloom." 5.48pm: Just 15 minutes to go, or so! We've moved the video player to the top of the blog for your viewing pleasure. John Philip Sousa, the American composer of that most venerable orchestral form – the march – is most famous for " The Washington Post " and " Semper Fidelis ." These tunes are so deeply ingrained in the national psyche that studies have shown them to be annoyingly stuck in the head of a full 30 percent of the population at any given time. Sousa was known as "The March King." And you know what calls for a march? A planet marching across the face of the sun. The December 1882 Transit of Venus lasted 6 hours and 18 minutes, according to NASA . The next year, Sousa published his "Transit of Venus" march .

It's about two minutes long, depending on your tempo, meaning that it could have been played on repeat approximately 189 times during the 1882 transit. Can you imagine hearing this 189 times in a row? 5.57pm: Cultural output inspired by the transit of Venus is not limited to the composition of marches. In 1880, two years before the second transit of the 19th century, the French painter Edmond Louis Dupain was commissioned to complete a grand allegorical painting of Venus crossing the sun. Venus devant le soleil by Edmond Louis Dupain (1886). The painting, completed in 1886, now adorns the ceiling of the western rotunda of the Perrault wing of the Paris Observatory. In the painting the sun is on a chariot surrounded by fog and rosy-cheeked nudes. Venus is naked, wearing a star on her head, attended by doves. 6.03pm: There it is! (There it is?) Venus touches the sun at 18:03:50 ET (=22.03.50 UT).

The ingress interior – when the planet is wholly in front of the sun – happens at 18:21:21. The transit center falls at 21:27:27; the egress interior at 24:33:33 and the egress exterior at 24:51:25. 6.07pm: Some viewers appear to be having trouble accessing the Nasa site. — Ever Lazz (@Everlazz) June 5, 2012 6.21pm: We have posted a new video feed of the transit at the top of the blog. Let us know if it's working. At 22:19:50 it looks like this: Venus begins her transit. Meanwhile keep an eye on that Nasa feed here . 6.32pm: The Nasa scientists viewing Venus as the planet passes fully onto the face of the sun are very thrilled. The tiny disc of Venus is crossing onto the sun in the 8 o'clock position.

You may be seeing images that make Venus look like it's entering the sun at around 2 o'clock; that is because depending on the type of telescope, the images you see will be reversed and sometimes flipped left to right. For those observers viewing the phenomenon directly, the planet appears to be crossing the sun from the lower left. 6.44pm: We have just spoken with Jason Kendall, who heads up Nasa's Solar System Ambassador Program in New York City. Jason is hosting an event in Riverside Park to watch the transit – and it has drawn almost a thousand attendees. Contacted by phone at the event, Kendall yells "What did we just see five minutes ago?" and raises his phone to the crowd. "Venus!!" a wave of exuberant yells comes back. "Almost 900 people are here on the pier," said Kendall. "We've been able to see it, despite the clouds. We saw second contact and now it's getting across. We've handed out a couple hundred sunglasses, and people are having a great time watching it, and it's a great succses here in NYC!" Kendall said the sun was lowering toward the Hudson but there were still a good two hours of viewing time left.

"We're kind of fortunate that we have clouds, because we're at capacity here," Kendall said. "I think the clouds discouraged some people." "They're having fun when they see it, it's very exciting when it comes out. It's officially a happening here in New York City!" 6.56pm: Venus at the start of its transit of the Sun. Handout image courtesy of Nasa shows the planet Venus at the start of its transit of the Sun, June 5, 2012. Photograph: Nasa/Reuters 7.09pm: Now for a little more on the incredible history of this spectacle. After Horrocks saw his transit in 1639, the next pair of transits to be observed happened in 1761 and 1769. And this time hundreds of astronomers were watching. They crossed the ocean, fought their way into Siberia, set up observation stations in the New World and the East Indies and even the Arctic. Multiple scientists, including the astronomer with Capt. James Cook, died at sea.

Some of the fatalities owed to the fact that the Seven Years War was still being fought at the time of the first transit, and English and French vessels attacked one another whenever they crossed. They all were acting at the behest of one man: Edmond Halley, who died in 1742. Why was Halley so eager that hordes of astronomers disperse to the ends of the Earth decades after his death to watch a planet pass between the Earth and the sun? Halley realized that accurate measurements of the time it took Venus to cross the sun, when taken from distant points on Earth, could be used to establish the distance between the Earth and Venus, and thus the distance between the Earth and the sun. The 17th century German mathematician Johannes Kepler had already calculated the proportional distances of the solar system. Thanks to Kepler, scientists knew that Jupiter is five times as far away from the sun as Earth is, for example. They knew the proportional distances. They just didn't know the absolute distances. This was the central quest of astronomy: to determine the size of the solar system. And suddenly Halley saw how it could be done, using the transit of Venus.

7.18pm: A very successful backyard capture of the transit. And the sun smiled upon us! #venustransit twitpic.com/9t7ern 7.25pm: The aforementioned John Philip Sousa, the renowned composer of the march " Transit of Venus, " among other marches, was also a novelist. He wrote the march in 1883, but Sousa wasn't done with the transit. In 1920 he published a novel called "The Transit of Venus." "The March King," John Philip Sousa, whose lesser-known works include "The Transit of Venus." Sousa was also a novelist and an expert trapshooter. Photograph: US Public domain. Here's the crucial scene, on page 221: The day of days for the expedition arrived. The observation of the transit was a superb success. The sky was clear, the sun shone brightly, and the little black disc we call Venus, situated between our planet and the sun, behaved like a real lady, and photographs and data of value were obtained. Riveting stuff.

Thanks to Google's work at digitizing the holdings of the New York Public library, you can read the entire novel, all 250 pages, online here. Do you know what else John Philip Sousa was preternaturally gifted at? Trapshooting. He apparently never missed. His induction page to the Trapshooting Hall of Fame, which exists, is here . 7.33pm: A beautiful image of the transit as seen from New York City, where we're about 50 minutes from sundown. Venus begins to cross the Sun's face during the transit of Venus as seen from the west side of Manhattan in New York. Photograph: Stan Honda/AFP/Getty Images 7.40pm: My colleague Katie Rogers has a dispatch from space – cyberspace: In a Google+ corner of the Internet, several professional and amateur astronomers from Vancouver Island to San Francisco have attached their telescopes to cameras and are "hanging out" in real-time. Fraser Cain, founder of space website Universe Today , said the group bumped its weekly "Virtual Star Party" to Tuesday in order to watch the event. Google+ user Fraser Cain What can a novice stargazer learn from this transit?

"Only six [transits] have occurred since the invention of the telescope," Cain said. "It's because of the transit of Venus that we even know how big the solar system is. It's one of the most fundamental observations that have ever been made in the history of astronomy." 7.49pm: Venus inside of the sun projected through a telescope onto a piece of cardboard on the Gold Coast, Queensland, Australia. Taken on the Gold Coast, Queensland, Australia. Jim White operates the telescope and bit of cardboard. Photograph: Warren Murray for the Guardian A moment captured by Guardian production editor Warren Murray. 7.57pm: In her magisterial " Chasing Venus: The Race to Measure the Heavens ," Andrea Wulf traces the dramatic transformation of Venus from object of mythological awe to instrument of scientific revelation. The Birth of Venus by Sandro Botticelli. Photograph: Summerfield Press/Corbis Here's Wulf: The Ancient Babylonians called her Ishtar, too the Greeks she was Aphrodite and to the Romans Venus – goddess of love, fertility, and beauty. She is the brightest star in the night sky and visible even on a clear day.

Some saw her as the harbinger of morning and evening, of new seasons or portentous times. She reigns as the 'Morning Star' or the 'Bringer of Light' for 260 days, and then disappears to rise again as the 'Evening Star' and the 'Bringer of Dawn.' Venus has inspired people for centuries, but in the 1760s astronomers believed that the planet held the answer to one of the biggest questions in science – she was the key to understanding the size of the solar system. 8.08pm: We've just passed the two-hour mark of Venus' 2012 transit of the sun, the last such transit of our lifetimes. The planet is about 30 percent of the way through its journey. In the below image, courtesy of Nasa, the path Venus is taking is flipped, so that it appears the planet is crossing the sun from the upper right. In fact, from our vantage, Venus is crossing the sun across the bottom from the lower left. Venus two hours into its 2012 transit of the sun. She looks a bit lonely out there. No?

8.18pm: How does the calculation of the size of the solar system based on observations of the transit of Venus work? The Exploratorium museum in San Francisco has an explainer that will be especially pleasing for readers with a passing acquaintance with math. Imagine two different people, one on each pole of the Earth, viewing the transit of Venus. The person on the North pole sees Venus following one path across the Sun. The person on the South pole sees Venus follow a slightly higher path, one that's shifted a little to the north. Because we see the Sun as a circle, these two different paths will have different lengths. Halley proposed that an easy way to measure the difference between the lengths of these two paths would be to time the transits, using the four phases of the transit—the first, second, third, and fourth contacts—as indicators. With the two different paths known, the distance between the Earth and the Sun can be pretty easily calculated using trigonometry and Kepler's third law of planetary motion. How the distance from the Earth to the sun is calculated using measurements of the transit of Venus, in a screen grab from the web site of the Exploratorium museum in San Francisco. Visit the Exploratorium here .

There's more trigonometry where that came from. 8.40pm: Captain James Cook, the legendary explorer who circled the world twice before being hacked to death on a Hawaiian beach midway through his third circumnavigation, who commanded the first English vessel to penetrate the Pacific Isles (where his crew launched an epidemic of venereal disease) and who became the first explorer to touch Australia's east coast, got his big start chasing the transit of Venus. At the request of the Royal Society, King George III commissioned an expedition to Tahiti to observe the 1769 transit from the cloudless and deeply southern skies of the Pacific. In "The Age of Wonder," Richard Holmes argues that Cook's great voyage marked the dawn of a golden age of Romantic science – romantic in the same sense that we have Romantic poetry. (The Age of Wonder ended, Holmes says, with the voyage of Charles Darwin's Beagle to the Galapagos islands in 1831.) Captain Cook: Photograph: Australian News And Info Bureau/taken from picture library Here's Holmes on Cook's trip: The Endeavour expedition remained for three months on Tahiti. Its main object was to observe a Transit of Venus across the face of the sun.

(Cook stated that this was the reason their settlement was named Fort Venus, though his junior officers gave a different explanation.) The expedition was organised by the Admiralty, but also partly financed by the Royal Society, which suppled L4,000 towards astronomical observations. [...] Through the brilliance of Cook's navigation, and the skill of his crew-management, the Endeavour arrived at Tahiti with over six weeks in which to prepare for its main task, the transit observations. Previous expeditions had often been decimated by this stage, but Cook had lost only four men, and none to disease. In an interview with the Guardian , historian Andrea Wulf summarized the results of the expedition and others around the world. They start calculating [the distance from the Earth to the sun] in the summer after the transit. But they have to wait for Cook to come back, in July 1771. Then they calculate and they come up with a range that goes from 93 million miles to 97 million miles. Today's value is just under 93 million. So they're pretty, pretty, pretty close. Compared to what they thought in the 17th century. So I think the result is pretty impressive.

8.56pm: One of the most pleasing ways to catch the transit of Venus is with a telescope projection. That's just what our production editor Warren Murray has got up to in a park on the Gold Coast, Queensland, Australia. He's cut this video with his wife, Lenny White, narrating, and her dad, Jim White, on telescope. If you've ever wondered how to start a fire with a telescope, you might watch through to the end. Can do, liliyaW! Here is a gallery of images of Venus making her transit – and of Earthlings watching it. Handout image courtesy of NASA shows the planet Venus at the start of its transit of the Sun, June 5, 2012. Photograph: Nasa/Reuters And here's a Nasa shot. The sun: it's hot. 9.07pm: In just 20 minutes, at 9.27.27pm ET, Venus will be exactly halfway through her 2012 trip across the sun.

9.15pm: And if you're really hungry for a universe of pictures of the transit of Venus, my colleague Katie Rogers points out, you can surf on over to Nasa's transit of Venus Flickr challenge page . The transit of Venus on Flickr. You want Venus? They got Venus . 9.33pm: Venus is now just over halfway through its 2012 transit of the sun. This image from Nasa shows the sun through a telescope with a purple filter. The telescope has projected a flipped image, so that Venus appears to have entered the sun from the right, when in fact it came in from the left. Venus halfway through her 2012 transit of the sun, in a Nasa screen grab. A NASA map of where on Earth the 2012 transit of Venus will be visible. Delisle figured it out 250 years ago. 11.30pm ET / 4.30am BST: Goodnight, Venus: The sun with its temporary alien mole has been down for nearly three hours now in New York. For us, the transit is well and truly over.

But as the sun comes up in the UK, it should be visible there, depending on the cloud cover. Coming up is the egress interior (12.33am ET, 5.33am BST) to be followed by the egress exterior 18 minutes later. And then we will never see it again. We're going to end this live blog now and join those of you watching the Nasa live feed . We want to thank you for reading and especially for all the insightful comments. Goodnight, Venus. Transit of Venus Across The Sun 2012: Clip :53 - The transit of Venus across the Sun has enthralled astronomers and amateur stargazers alike. They gathered across the world to view the rare phenomenon. The planet appeared as a small black pinhole moving slowly across the face of our Sun. People turned their gaze to the small silhouette of Venus in a spectacle that will not be seen again until 2117. NOTE: NO NARRATIONS by Russia Today Clip :53 - The transit of Venus across the Sun has enthralled astronomers and amateur stargazers alike. They gathered across the world to view the rare phenomenon.

The planet appeared as a small black pinhole moving slowly across the face of our Sun. People turned their gaze to the small silhouette of Venus in a spectacle that will not be seen again until 2117. NOTE: NO NARRATIONS Get the Playrific Classical Historian app today - The Classical Historian - History Learning Games and Educational Activities Playrific makes childrens apps with exciting, intelligent, educational & fun content from around the world. Related ServiAstro What is the "black drop" effect? What is a transit? A transit is the crossing of a planet or any other celestial body in front of the Sun. Among the Solar System planets, only Mercury and Venus can transit across the Sun because they orbit closer in than the Earth. The Moon can also transit across the Sun and this is what we know as a solar eclipse. What can we see during a transit? During a transit we can see the disc of the planet projected on the bright surface of the Sun. The planet appears as a small dark disc (because of the brightness contrast between the night hemisphere of the planet and the surface of the Sun) that changes in position with time.

The apparent size of Venus seen from Earth is about 30 times smaller than the size of the sun. By comparison, Mercury shows an apparent disk about 160 times smaller than the sun. How can we observe a transit? NEVER LOOK AT THE SUN DIRECTLY. Looking at the Sun directly without protection or trough eyeglasses (including sunglasses), telescopes or any other instrument not designed for solar observation may result in severe eye injury and blindness. Because of the small apparent size of Mercury, it will be impossible to observe the planet's disc during the transit unless aided with an optical instrument. The safest way to observe the transit is by projecting the image of the Sun trough a telescope onto a white screen (see figure below). In addition, this procedure permits the simultaneous observation of the phenomenon to a group of people. The case of Venus is slightly more favourable, because of its larger size it might be observable with the naked eye (ALWAYS UTILIZING A SOLAR FILTER). However, the projection method will yield a better viewing of the event. How often does a transit of Mercury occur? The last transit of Mercury were: November 15, 1999.

This traffic, however, was not visible from any point of Spain in any of its phases. November 10, 1973, visible from Spain. May 7, 2003, the last transit visible from Spain. Webcasted by ServiAstro November 8, 2006. Invisible from Spain And a transit of Venus? The last pair of transits of Venus occurred on June 5 2012 and June 8 2004 . The transit of 2012 was hardly visible from the mainland, the 2004 change was visible in all its stages from all over the peninsula. The previous pair of transits of Venus occurred in 1874 and 1882. Only the second was partially visible from Spain. When did the last transit take place? The last transit of Mercury was on November 15, 1999. This transit, however, was not visible from Europe during any of its phases. The last transit visible from Europe occurred on November 10, 1973.

In the case of Venus the last pair of transits took place during 1874 and 1882. Only the second one was observable from Europe. When will the next transits occur? The next transit of Mercury will be on November 11, 2019 and from the mainland will be visible only in part, because the sun will set before the transit finished. The next pair of transits of Venus will occur the years 2117 and 2125. How long does the May 9 transit last for? The transit of Mercury of May 9, 2016, has an approximate duration of 7 hours and 30 minutes. In the most faourable cases, a transit of Mercury can last for up to 8 hours. On average, the transits that occur on November are shorter than those occurring on May, because the former take place when Mercury is closer to its perihelion (minimum orbital distance from the Sun) and, by Kepler's Second Law, it moves faster than near the aphelion (in years with transit, Mercury has its aphelion shortly before the beginning of May).

The maximum duration of a transit of Venus is also slightly over 8 hours. How does Mercury look like? Mercury is the planet closest to the Sun. It is prossibly the poorest known planet of the Solar System (besides Pluto). It has only been visited by one space mission, Mariner 10, in 1973 and 1974, which was just able to take images of one of its hemispheres. The picture resulting from Mariner's 10 observations is that of a planet without atmosphere and with a surface populated with numerous impact craters. Some characteristics of Mercury (from Astronomï¿½a General Teï¿½rica y Prï¿½ctica. D.Galadï¿½-Enrï¿½quez & J.

Gutiï¿½rrez Cabello) Mass 0.055 Solar masses Equatorial radius 2439 km Mean density 5.43 g/cm3 Rotation period 58.646 days Orbital period 87.969 days Average distance to the Sun 0.3871 AU (57900000 km) Orbital eccentricity 0.206 Orbital inclination 7.0 degrees Who was the first person to observe a transit? The first observation of a transit of Mercury was registered in 1631 by the French astronomer Pierre Gassendi. Even though the telescope, necessary to observe the transits, was in use since until approximately 1610, no one observed the transits of 1615, 1618 and 1628, because their occurrence was not known. The release of new tables with more accurate positions of the planets (the Rudolphine Tables of Kepler in 1627) made possible the prediction and observation of the transit of 1931. The first transit of Venus was observed in 1939 by the briton J.

Horrocks. As it turns out, Kepler had predicted a transit of Venus for 1931. However, despite the efforts of Gassendi, the transit was not observed because it occurred during nighttime in France (this fact was obviously unknown to Gassendi because of the limited accuracy of Kepler's tables). Kepler, however, did not predict a transit for 1639. It was Horrocks himself who, on October 1639, when comparing Kepler's tables with the older and inaccurate tables of Lansberg, realized that the latter were predicting a possible transit of Venus on November of the same year. Horrocks confirmed the prediction with his own calculations but the short time available caused that the event was not widely announced. Thus, only Horrocks, his brother Jonas and his friend Crabtree were aware of the occurrence with enough anticipation. Both Horrocks and Crabtree observed the transit and took some measurements but it seems that Horrock's brother never observed it. What scientific importance has a transit? Currently, the transits of Mercury are just a curiosity with almost no scientific interest. The same can be said of the transits of Venus.

Among the few contributions that Mercury's transits can make today is the study of Earth's rotational velocity. When the circumstances of a transit observed in the past are known (i.e., contact times and observing site), one can eventually infer small variations of the length of the day along the centuries. The situation, however, was radically different up to the XIXth century. Until then, the transits of Venus, as suggested by Edmond Halley in 1716 , had been used to attempt an accurate measure of the mean distance between the Earth and the Sun, namely the Astronomical Unit. Many scientific expeditions were organized to observe the transits of 1761, 1769, 1874 and 1882. But, in spite of all the efforts, several observational limitations, most notably the black drop effect, made impossible a sufficiently accurate determination of the Astronomical Unit through the method of the transits of Venus. During the second half of the XIXth century and along the XXth century, new methods were developed to determine the Earth-Sun distance, none of them implying the transit of Venus or Mercury across the Sun.

The past strong scientific interest of these events was therefore lost. Currently, only phenomena derived from the transits such as the mentioned black drop effect are subject of observation and study. What is the "black drop" effect? Shortly after the internal contact between the discs of the Sun and the planet (Mercury or Venus) something strange occurs. Instead of separating clearly from the solar limb, the disc of the planet seems to stick for a few seconds to the solar disc, and experiences a deformation in the appearance of a black drop. The same phenomenon repeats again just before the last internal contact. . The effect of the black drop prevents an accurate registration of the times of contact between the disc of the planet and the Sun, and was the chief cause of the failure of the attempts to determine the Earth-Sun distance using Halley's method. The main cause of the occurrence of this phenomenon is the turbulence of Earth's atmosphere, albeit the solar disc being slightly darker at the edge than at its center (known as limb darkening) is also partly responsible. We can simulate the black drop effect by joining our fingers slowly and observing the resulting shadow.

Just before they reach contact a meniscus-shaped shadow arises and seems to join the fingers together, similarly to what occurs between the limb of the Sun and the planet. If you want a more complete explanation of the black drop effect follow the link (in English, very technical). The 2012 Transit of Venus | NASA The 2012 Transit of Venus May 24, 2012 [image-63] On June 5th, 2012, Venus will pass across the face of the sun, producing a silhouette that no one alive today will likely see again. Transits of Venus are very rare, coming in pairs separated by more than a hundred years. This June's transit, the bookend of a 2004-2012 pair, won't be repeated until the year 2117. Fortunately, the event is widely visible. Observers on seven continents, even a sliver of Antarctica, will be in position to see it. The nearly 7-hour transit begins at 3:09 pm Pacific Daylight Time (22:09 UT) on June 5th.

The timing favors observers in the mid-Pacific where the sun is high overhead during the crossing. In the USA, the transit will be at its best around sunset. That's good, too. Creative photographers will have a field day imaging the swollen red sun "punctured" by the circular disk of Venus. Observing tip: Do not stare at the sun. Venus covers too little of the solar disk to block the blinding glare. Instead, use some type of projection technique or a solar filter. A #14 welder's glass is a good choice. Many astronomy clubs will have solar telescopes set up to observe the event; contact your local club for details. Transits of Venus first gained worldwide attention in the 18th century. In those days, the size of the solar system was one of the biggest mysteries of science. The relative spacing of planets was known, but not their absolute distances. How many miles would you have to travel to reach another world? The answer was as mysterious then as the nature of dark energy is now. Venus was the key, according to astronomer Edmund Halley.

He realized that by observing transits from widely-spaced locations on Earth it should be possible to triangulate the distance to Venus using the principles of parallax. The idea galvanized scientists who set off on expeditions around the world to view a pair of transits in the 1760s. The great explorer James Cook himself was dispatched to observe one from Tahiti, a place as alien to 18th-century Europeans as the Moon or Mars might seem to us now. Some historians have called the international effort the "the Apollo program of the 18th century." [image-51]In retrospect, the experiment falls into the category of things that sound better than they actually are. Bad weather, primitive optics, and the natural "fuzziness" of Venus’s atmosphere and other factors prevented those early observers from gathering the data they needed. Proper timing of a transit would have to wait for the invention of photography in the century after Cook’s voyage. In the late 1800s, astronomers armed with cameras finally measured the size of the Solar System as Edmund Halley had suggested. This year’s transit is the second of an 8-year pair.

Anticipation was high in June 2004 as Venus approached the sun. No one alive at the time had seen a Transit of Venus with their own eyes, and the hand-drawn sketches and grainy photos of previous centuries scarcely prepared them for what was about to happen. Modern solar telescopes captured unprecedented view of Venus’s atmosphere backlit by solar fire. They saw Venus transiting the sun’s ghostly corona, and gliding past magnetic filaments big enough to swallow the planet whole. 2012 should be even better as cameras and solar telescopes have improved. Moreover, NASA’s Solar Dynamics Observatory is going to be watching too. SDO will produce Hubble-quality images of this rare event. [image-36] The 2012 Transit of Venus | Science Mission Directorate Science Mission Directorate Join Mailing List May 18, 2012: On June 5th, 2012, Venus will pass across the face of the sun, producing a silhouette that no one alive today will likely see again. Transits of Venus are very rare, coming in pairs separated by more than a hundred years.

This June's transit, the bookend of a 2004-2012 pair, won't be repeated until the year 2117. Fortunately, the event is widely visible. Observers on seven continents, even a sliver of Antarctica, will be in position to see it. Click on the image to view a ScienceCast video about the 2012 Transit of Venus. Photo credit: David Finlay of Sydney, Australia (June 8, 2004). The nearly 7-hour transit begins at 3:09 pm Pacific Daylight Time (22:09 UT) on June 5th. The timing favors observers in the mid-Pacific where the sun is high overhead during the crossing. In the USA, the transit will at its best around sunset. That's good, too. Creative photographers will have a field day imaging the swollen red sun "punctured" by the circular disk of Venus. Observing tip: Do not stare at the sun. Venus covers too little of the solar disk to block the blinding glare. Instead, use some type of projection technique or a solar filter. A #14 welder's glass is a good choice.

Many astronomy clubs will have solar telescopes set up to observe the event; contact your local club for details. The June 8, 2004, transit of Venus photographed by Frans Snik at the Dutch Open Telescope in La Palma, Canary Islands. [ more ] Transits of Venus first gained worldwide attention in the 18th century. In those days, the size of the solar system was one of the biggest mysteries of science. The relative spacing of planets was known, but not their absolute distances. How many miles would you have to travel to reach another world? The answer was as mysterious then as the nature of dark energy is now. Venus was the key, according to astronomer Edmund Halley. He realized that by observing transits from widely-spaced locations on Earth it should be possible to triangulate the distance to Venus using the principles of parallax. The idea galvanized scientists who set off on expeditions around the world to view a pair of transits in the 1760s. The great explorer James Cook himself was dispatched to observe one from Tahiti, a place as alien to 18th-century Europeans as the Moon or Mars might seem to us now.

Some historians have called the international effort the "the Apollo program of the 18th century." In retrospect, the experiment falls into the category of things that sound better than they actually are. Bad weather, primitive optics, the natural "fuzziness" of Venus’s atmosphere, and other factors prevented those early observers from gathering the data they needed. Proper timing of a transit would have to wait for the invention of photography in the century after Cook’s voyage. In the late 1800s, astronomers armed with cameras finally measured the size of the Solar System as Edmund Halley had suggested. A double transit: the ISS+Venus on June 8, 2004. Photo credit: Tomas Maruska of Stupava, Slovakia [ more ] This year’s transit is the second of an 8-year pair. Anticipation was high in June 2004 as Venus approached the sun. No one alive at the time had seen a Transit of Venus with their own eyes, and the hand-drawn sketches and grainy photos of previous centuries scarcely prepared them for what was about to happen. Modern solar telescopes captured unprecedented view of Venus’s atmosphere backlit by solar fire.

They saw Venus transiting the sun’s ghostly corona, and gliding past magnetic filaments big enough to swallow the planet whole. One photographer even caught a spaceship, the International Space Station, transiting the sun alongside Venus. 2012 should be even better as cameras and solar telescopes have improved. Moreover, NASA’s Solar Dynamics Observatory is going to be watching too. SDO will produce Hubble-quality images of this rare event. For more news and information as the date of transit approaches, stay tuned to .

Question: Which planet did a transit across the sun in 2012?
Answer: VENUS