Transit of Venus

Transit of Venus on 5 and 6 June 2012

June 6, 2012, Venus will pass in front of the huge Sun, specialists talk transit of Venus. Venus between Earth and the Sun, obscures a small part of the solar disk. This unique astronomical event will not happen again 105 years before, in December 2117, although the previous transit of Venus took place on 8 June 2004, this event is relatively rare because after a cycle of two transits in the space of eight years, it happens over a century to see the following. Kepler predicted the transit of Venus on December 7, 1631 but died a year earlier. This transit of 1631 was not observed by astronomers since Kepler's calculations proclaimed the passage at night, when he was a visible part of the day. This is the English clergyman Jeremiah Horrocks (1619-1641) predicted that the second passage after eight years, that of December 4, 1639. The Venus transit of 1731 was the subject of the first campaign of international scientific observation. This transit was observed from different locations on the planet by astronomers of the time to calculate the astronomical unit, i.e. the distance between the Earth / Sun. Measurements of the time were very approximate because scientists have found values ​​between 130 and 158 million kilometers. Currently we use the spacecraft telemetry and radar to calculate the value of the astronomical unit with very high accuracy (few meters), the parallax method has become obsolete. The event of June 2012 is long overdue and astronomers around the world are prepared, coordinating a number of observations.
Even the Hubble Space Telescope observed the eclipse through the spectrometer, an original way.

Of course, Hubble will not point directly at the sun, but it will be directed to the moon to try to capture the small variation in brightness caused by the passage of Venus across the Sun. This type of observation is already used for the detection of exoplanets. In France it is only from 6:37 until 5:50 ET as the end of the transit will be observable and takes about one hour. At 6:55 Venus touches the western edge of the Sun. The mean diameter of Venus is 12 103.6 km while the mean diameter of the Sun is 1,392,000 km, 115 times larger.

NB: For astronomers, the four interesting moments during the transit of Venus are when the circumference of Venus is tangent to that of the solar disk.
- First contact, Venus enters the sun's disk touches the outer edge of the Sun.
- Second contact, Venus is in the solar disc and touches the inner edge of the Sun.
- Third contact, Venus out of the solar disk and touches the inner edge of the Sun.
- Fourth contact, Venus out of the solar disc and touches the outer edge of the Sun.

Image: 3rd contact of the transit of Venus across the Sun June 6, 2012 at 4:37 UT.

Image: The most beautiful pictures of the 2012 Venus transit were taken outside the Earth's atmosphere by the satellite SDO (Solar Dynamics Observatory).
Eighth transit of Venus across the Sun, since the observation with telescopes. Venus is visible in the upper left of the image, out of the sun. Of 5 to 6 June 2012, we can see the progress of the transit of Venus across the Sun, 5th at sunset for North Americans, the six at sunrise for Europeans. A transit of Venus is like a solar eclipse by the Moon, Venus four times larger than the Moon, appears smaller because it is nearest from Earth.
Credit: NASA/SDO, AIA

Venus Transit of June 8, 2004

The previous transit of Venus was observed from the Earth June 8, 2004. This was the first transit of Venus after the appearance of telecommunications. If anyone had seen the previous transit, that of December 6, 1882, many were able to admire the 2004.
The transit of Venus across the Sun of 2004 was one of the best documented astronomical events.
Many images showed transit from Europe, Asia, Africa and North America. These pictures have immortalized this event that is rare transit of Venus across the Sun. Some images showed a double transit of Venus and a plane, or Venus and the International Space Station.
Other images mingled with the event a foreground cloud.

Image: Photo: Marcin Filipek/Polish Association of Amateur Astronomers.

Transit of Venus on 5 and 6 June 2012

During the transit of Venus of June 6, 2012, European observers were particularly disadvantaged because this transit took place between 0:10 ET 6:50 pm Paris time (10:10 p.m. and 4:50 Universal Time). The sun was below the horizon. Venus appeared black, perfectly round and sharply defined on shiny background. Transits of Venus are the rarest eclipses visible from Earth, much rarer than eclipses of the Sun by the Moon or Mercury. The last transit of Venus before 2117, was one of the celestial phenomena the most photographed plenty of history. This live image of the Sun is taken by the SDO satellite. Venus appears to us here, much higher than in reality because of its position relative to the Earth and the Sun, where it is located at 1/3 the distance from the Earth / Sun, we see 2/3 too large. Venus, on the actual image is 33 times smaller than the Sun when in reality it is 115 times smaller.
Credit: NASA / SDO & the AIA, EVE, and HMI teams.

NB: Launched February 11, 2010, SDO is the most sophisticated spacecraft ever designed to study the sun. It is placed in a geosynchronous orbit, a geocentric orbit of a satellite which moves in the same direction as the Earth (from west to east), and whose orbital period is equal to the sidereal rotation period of the Earth (about 23 h 56 min 4.1 s). This orbit has a semi major axis of about 42 200 km.

Image: Venus transit of June 6, 2012 0:32 (UT).