From Earth's perspective, on June 5 and 6, Venus will pass across the face of the Sun. By observing the tiny fraction of sunlight that passes through Venus's atmosphere using the Hubble Space Telescope, it is hoped that the planet's atmospheric makeup can be determined. Though we already know the nature of Venus's atmosphere, it is hoped the event will help astronomers hone techniques, already in use, that may one day help to identify Earth-like planets in far-away solar systems. The catch? Hubble cannot observe the Sun directly. Instead it will look at the Moon to observe reflected light.
Read the full article: Hubble to use Moon as giant mirror to observe Venus transit