The transit of Venus occurs when it is between the Earth and the Sun, on the same line with them. The rarity of this phenomenon is explained by the fact that the plane of the orbit Earth and Venus are angled relative to each other. Transits occur in pairs - two of the December passage with an interval of eight years, then two of June, with the same interval of time between them. The interval between the pair - 121.5 years, and between the second pair and the end of the cycle - 105.5. Then everything is repeated. The entire cycle of 243 years. Thus, the next pair of transits will be seen in 2117 and 2125 respectively.
The duration of the cycle - the value is stable. But the sequence of intervals between the passage changes. The existing will continue until 2846. In subsequent years, the interval between pairs of transits will be 129.5 years.
In 2012, the "small parade of planets" could be observed in almost all parts of the globe. The exception was South America, West Africa and Antarctica. In Russia, this phenomenon was observed almost everywhere but fully only in the Far East and in the northern regions of the country.
Transit of Venus 2012 watched with great interest the scientists and astronomers - fans all over the world. In particular, it was involved an orbital telescope "Hubble". It was aimed at the moon, because the intensity of solar radiation could damage the image sensor. The scientists were to detect a change of brightness satellite, due to the fact that a small part of the sun was closed by Venus, and, with the help of spectroscopy to investigate the chemical composition of its atmosphere. With the experiment was planned to determine whether it is possible by this method to study the atmospheres of other planets.
It was used as a probe NASA SDO, Hinode Japanese and European "Venus Express". Last I worked with a team of scientists on Svalbard. There was also an experiment "Twilight of Venus", during which the researchers observed the transit at the same time from different regions of the world. In particular, it was planned to figure out how in 1761 Mikhail Lomonosov discovered the atmosphere of Venus, and a more detailed study of its composition. For transit was also observed by the crew of the International Space Station.