As its June 6
2012 transit begins
Earth's sister planet
crosses the edge of the Sun in this stunning
from the Hinode spacecraft.
The timing of limb crossings during the
rare transits was used historically to
the distance to Venus and
determine a value for the Earth-Sun distance
called the astronomical unit.
like this one show the event against
an evocative backdrop of the turbulent solar surface with prominences
lofted above the Sun's edge by twisting magnetic fields.
Remarkably, the thin ring of light seen surrounding the planet's dark
silhouette is sunlight refracted by
Venus' thick atmosphere.