Destinations:
A transit is the passing of an apparently smaller object in front of an apparently larger object from a specific vantage point. In our solar system, events traditionally defined as transits include the passing of
Mercury and
Venus across the
sun. As seen from Earth, only transits of the inner planets
Mercury and
Venus are possible. Planetary transits are far more rare than eclipses of the sun by the moon. On average, there are thirteen transits of
Mercury each century. In comparison, transits of
Venus usually occur in pairs with eight years separating the two events.
Now that we have spacecraft in multiple vantage points in our solar system, we observe more transits than from only Earth and in better detail. For example, the transit of Ariel across Uranus was recently observed by the Hubble Space Telescope. We have also used transits to our advantage to discover other planets around other stars. A transit occurs when a planet passes across the disk of its parent star. Not unlike an eclipse, when transits are observed, the planet passing in front of the star causes a reduction of the star's brightness as seen from Earth. This is one of several methods used to find exo-planets orbiting stars in distant planetary systems.
Missions:
Although it will not observe the Mercury transit, The MESSENGER mission is still on its way to Mercury. Its next milestone is the second flyby of Venus in June 2007 as it continues to get closer in to Mercury's orbit.
Mars Reconnaissance Orbiter now orbiting Mars, begins its principle science phase this month.
The Kepler Mission, a NASA Discovery mission planned for a 2012 launch, will observe transits of stars within our Milky Way galaxy to detect and characterize Earth-size and smaller planets. Results from this mission will allow us to place our solar system within the continuum of planetary systems in the galaxy.
Features:
There are several features on our website to help you learn more about transits and Mercury- Discover Mercury: The 2006 Transit , the historical perspective of a 2004 Venus transit and Mercury unveiled.
Fast Lesson Finder:
K-12 Activities: Search our Fast Lesson Finder to find classroom lessons related to our solar system and beyond. Some activities related to this month's theme includes Searching for Habitable Worlds and Sensing the Invisible from the MESSENGER mission.
People:
Meet T. Adrian Hill: A master of many trades on the MESSENGER and New Horizons missions.
Other Themes
