The Venus Twilight Experiment
Refraction and scattering phenomena during the transit of Venus on June 5-6, 2012
Planetary transits are a powerful method for discovering and characterizing exoplanets, but no transits can be seen in more details than those involving our own Solar System members, such as the transits of Venus and Mercury in front of the Sun.
|A. and S. Rondi - June 8, 2004 |
During and around Venus transits, in particular, interesting phenomena occurs, related to physical and chemical properties of its atmosphere. During ingress and egress a bright and thin luminous arc (the "aureole") is observable, appearing around the circumference of Venus disk which is partially outside the solar limb. This peculiar aspect of the planet has been observed for the first time in 1761 and then in all the subsequent transits, with varying intensity and aspect. Farther away from the Sun, the aureole - due to light refraction - disappears and Venus shines from the light diffused by droplets dispersed above its thick cloud deck.
We are establishing an international collaboration for deploying specialized instruments in the transit visibility area. We also realy upon the collaboration of observers that will use professional instruments at several sites. The multi-wavelength data will be interpreted thanks to a numerical model capable of reproducing the observations.
Our final aims are a better characterization of these twilight phenomena
and - in turn - an improved undestarding of the atmosphere of Venus, jointly with the observations obtained by Venus Express, the probe now orbiting the planet.
keywords: Venus transit 2012, Venus aureole, twilight phenomena, twilight experiment, Venus Express, Venus atmosphere, coronagraph, coronography, cytherograph, planetary transits