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Rare transit of Venus to be visible 5-6 June | Venus will cross the face of the Sun on 5-6 June,
a rare occurrence that will not be seen again for over a hundred years. ESA’s
Venus Express, a spacecraft orbiting the planet, will be reporting the event live
from the Arctic island of Spitsbergen . And the Venus Express science team will
be discussing the latest scientific results from the mission while enjoying a
unique view of the 2012 transit under the ’midnight Sun’. A transit of Venus occurs
only when Venus passes directly between the Sun and Earth. Since the orbital plane
of Venus is not exactly aligned with that of Earth, transits occur very rarely,
in pairs eight years apart but separated by more than a century. The last transit
was enjoyed in June 2004 but the next will not be seen until 2117. Venus transits
are of great historical significance because they gave astronomers a way to measure
the size of the Solar System. The transits of the 18th century enabled astronomers
to calculate the distance to the Sun by timing how long it took for Venus to cross
the solar disc from different locations on Earth and then using simple trigonometry.
Also, during the transit of 1761 astronomers noticed a halo of light around the
planet’s dark edge, revealing Venus to have an atmosphere. Thanks to spacecraft
that have since visited Venus, including Venus Express, we now know that it hosts
an inhospitable dense atmosphere of carbon dioxide and nitrogen with clouds of
sulphuric acid. Today transit events are a valuable tool for developing methods
for detecting and characterising planets orbiting other stars than the Sun, planets
that astronomers refer to as exoplanets. As a planet passes in front of a star,
it temporarily blocks out a tiny portion of the starlight, revealing its presence
and providing information about the planet’s size. Europe ’s CoRot space telescope
has used this technique to discover over 20 exoplanets. Transits are also being
used to search for exoplanets that may harbor life. If the planet has an atmosphere
a small fraction of the light from the star will pass through this atmosphere
and reveal its properties, such as the presence of water or methane. During next
month’s transit, astronomers will have the chance to test these techniques and
add to the data collected during only six previous Venus transits observed since
the invention of the telescope in the early 1600s. The 2012 transit will be visible
in its entirety only from the western Pacific, eastern Asia, eastern Australia
and high northern latitudes. For the US , the transit will begin in the afternoon
of 5 June and for much of Europe the Sun will rise on 6 June with the transit
almost finished.
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