Venus Transit 2012 and some facts about Venus

(Image Nasa Venus transit 2004)
On June 6^th. (in Europe) a historical astronomical event will take place. And as long as this is the last time in our lifetimes that we will be able to watch this event, because it happens next on the 11th. of December 2117, i though to bring it to your attention. And so that this does not become comepletly OT, i will add some facts about Venus itself and about the planets volcanism.

Image found on Flickr

In case the sky is overcast you can watch several livestreams: (If you watch them all, you will be really busy;)

• Several Countries: Coca-Cola Space Science Center
• Several Countries: NASA
• Several Countries: NISP
• Several Countries: Planethunters.org
• Several Countries: SLOOH
• Australia: ESA
• Australia: Sky-live.tv
• Germany: AstroNation
• Germany: Astronomie-Werkstatt “Sterne ohne Grenzen”
• Hawaii: Exploratorium
• Hawaii: Keck Observatory
• Hawaii: NASA
• India: Gurudev Observatory
• India: SPACE
• Israel: Bareket Observatory
• Japan: Kyoto University Kwasan Astronomical Observatory
• Japan: Sky-live.tv
• Norway: Andøa Rocket Range
• Norway: Interstellarum
• Norway: Sky-live.tv
• Norway: Viten.no
• Sweden: Alexander Birkner
• Sweden: Venustransit.de
• Svalbard: Departament d’Astronomia i Meteorologia, Universitat de Barcelona
• Svalbard: ESA
• USA: Appalachian State University
• USA: Astronomers without Borders
• USA (Alaska): University of North Dakota
• From Space (von der ISS): NASA
• Updated with a link from Sissel: View from Norway.

Hubble will turn to the moon to watch the transit. From the light that reflects from the moon Nasa wants to draw conclusions about Venus atmosphere. Of course the gases in Venus atmosphere are well known but by studying the results scientists hope to learn how to study atmospheres of extrasolar planets..

Historical transits of Venus
Most likely no human being ever watched a this event before the year 1639 even though it is visible to the naked eye and no shade to the eyes is necessary when the sun is close to the horizon. But you need very good calculations to be prepared and try to glimpse it and those calculations were not available till much later. There are hints that the Persian astronomer Avicenna could maybe have watched the transit in 1032.
1627 Johannes Kepler published Ephemarides in his “Rudoliphinische Tafeln, Rudolphine Tables“. Predicting a Venustransit for 1631 but could not watch it due to his death 1630.

Transit of Venus,  December 4^th 1639

Kepler predicted the next Venus transit for 1761 because he thought in 1639 Venus would miss the sun, but the young british astronomer Jeremiah Horrocks, recalculated in late November 1639 and found the next transit due on December 4^th 1639. He and his friend William Crabtree were probably the fist humans to ever watch such an event and still humankind would have forgotten about it, if Johannes Hevelius  would not have published the report by Horrocks in 1662. Horrocks calculated the Suns Parallax too and found the sun is much farther away than previously thought.

Edmond Halley viewed a transit of Mercury in 1677 and reached the conclusion that with accurate spottings of transits of Mercury and Venus the distance between earth and the Sun could be determined. The method he developed using triangulation,  states that the next transit should be viewed from different spots on earth, as far apart as possible. He knew he would not live to see the next acurance due in 1761 but sent out an urgent request, that his methods should be used with the next transit of Venus.

( Here is a german paper on how Halley calculated the transit,with graphics)

Transit of Venus, June 5^th. 1761

On June 5, 1761 the transit of Venus was observed by 176 scientists from 117 stations all over the world.

The precise observation was hindered through a phenomenon called the ”black drop” As a result the distance to the sun was calculated to be between 125 and 155 million kilometer.

You can find a list of all scientists and locations in this paper http://www.transitofvenus.nl/history.html#1761

The Russian scientist Michail Lomonossow noticed a seam around the planet and concluded that Venus has an atmosphere.

Transit of Venus 3^rd. of June 1769

Again many expeditions were sent out to observe the transit from different places on Earth. The most famous scientist watching this transit was James Cook who observed from Point Venus set up by him on Tahiti, during his voyage around the world. Again the “black drop” caused a disturbance, but the scientists knew it would happen and were better prepared. Later Jerome Lalande calculated the distance to the sun to153 +/-1million kilometer which is accurate up to 2% of the real distance, so Halley´s method had proved to give good results.

Even though there were different methodes to distiguish the solar parallax by then, the transits of Venus 1874 and 1882 rose even more scientific research programms worldwide and 1874 was used as a rehearsal for 1882.

In 2004 the distance earth sun was known with an accuracy of 100 meter, still the scientists recalculated the solar parallax again,partlyjust becauseof the fun torelive the workof the scientists in earlier days. The famous “black drop” could not be watched, so it was probaly due to lesser quality of the ancient telescopes. Here is a page on it by ESO the Eruopean South Observatory

Source: http://www.venustransit.de/venustransits.htm#y1032, among other sources.

Some facts about Venus (link toWikipedia)

Images taken from Wikipedia and by the Nasa´s Magelan probe.

Venus (link to Nasa) is the closest neigbour of the earth and its “sisterplanet” being about the same size. It revolves on an orbit second closest to the sun. To humanity it is known as the morning star as well as the evening star. It has a very thick atmosphere due, supposedly, to a “run away green house effect”. It spins opposite to all other planets and so a day on Venus is longer than a Venus-year.

Venus Volcanism

• Erik Klemetti devoted an article on eruptions to Venus: Dating Volcanic Eruptions on Venus
• New evidence of recent volcanism on Venus. ESA
• Volcanoeson Venus, Oregon Sate University
• How volcanoes work: Volcanoes on Venus

“The surface of Venus is dominated by volcanism and has produced more volcanoes than any other planet in the solar system. It has a surface that is 90% basalt, and about 65% of the planet consists of a mosaic of volcanic lava plains, indicating that volcanism played a major role in shaping its surface. The planet may have had a major global resurfacing event about 500 million years ago,from what scientists can tell from the density of impact craters on the surface. ” (  Wikipedia)

There are different types of volcanoes to be found on Venus.

Central-vent volcanoes: Like shield volcanoes on earth they are characterized by the radially dispersed lava flows extruded by the summit of the mountain. Some of those Volcanoes are really huge and have a diameter from around 100 kilometer. Two of the largest of these are Sif Mons (2 km high and 200 km in diameter) and Sapas Mons (1.5 km high and 400 km in diameter):
Pancake Domes: This variation of volcanoes are not found on earth and maybe unique. The pancakes are thought to be formed by highly viscous, silica-rich lava erupting under Venus’s high atmospheric pressure.
Scalloped margin domes or Ticks: The center appears like a dome but around the structure one can find odd lavaflows. The Ticks are not well understood.
Calderas: Like on earth those features most likely origin in a surface collapse, similar to those found on earth.
Arachnoids: They are so named because they resemble a spider’s web, featuring several concentric ovals surrounded by a complex network of radial fractures. It is not known whether the 250 or so features identified as arachnoids actually share a common origin or are the result of different geological processes.
Corona: A corona is immense circular to oblong structures, generally between 200 and 250 kilometer in diameter, although some can be as large as 1100 km across. These features appear to be unique to Venus.

Images of the Moon, Venus and Jupiter taken on March 3^rd. and 4^th. on my veranda with my mobile phone.

Spica

Additional information:

Venus Transit: A celestial rarity by Nasa.

Source SPACE.com: All about our solar system, outer space and exploration