astroengine writes: "On June 5 or 6 this year — the exact time and date depends on where you are in the world — Venus will be visible as a small black circle crossing the disk of the sun. Usually, the Hubble Space Telescope would have no business observing this event — the sun is too close for its optics. But plans are afoot for Hubble to observe the reflected sunlight bouncing off the lunar surface during the transit. As the sunlight will pass through the Venusian atmosphere, the transit will provide invaluable spectroscopic data about Venus' atmospheric composition. This, in turn, will help astronomers in characterizing the atmospheres of planets orbiting other stars."