As seen from Earth, Mercury appears to cross the disk of the sun — an event known as a transit — only about 13 times per century. Currently, transits of Mercury always occur in either May or November (this changes over hundreds of years), with spring transits only occurring about a third of the time.
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"During May transits, Mercury's closer to us, …show more content…
The last transit of Mercury took place in 2006, and the next one will occur in 2019. Although the rocky planet appears larger in May, the spring transits are rarer; the next one won't happen until 2049.
Searching for other worlds
During Monday's 7.5-hour transit, scientists will use the giant New Solar Telescope at the Big Bear Solar Observatory in California to try to catch a glimpse of sodium in the planet's thin atmosphere. A planet's atmosphere extends slightly above its surface, so starlight can illuminate the atmosphere when the planet passes in front of a star. On Monday, the scientists hope their observations will help them to better understand how sodium is released from the planet's surface.
Mercury isn't the only planet that transits the sun. Venus makes even less-frequent passages as seen from the Earth — Venus transits the sun in pairs, with the second transit occurring about 8 years after the first. However, the pairs are separated by about a …show more content…
NASA's Kepler Space Telescope studied other stars to search for the faint dimming of light that occurs when a planet passes between the disk of the star and the telescope. According to Jay Pasachoff, a professor at Williams College in Massachusetts who will be at Big Bear on May 9, the dimming of light from the 2003 and 2006 transits of Mercury were too faint to be detected, opening a door to understanding the limits of Kepler and the upcoming Transiting Exoplanet Survey Satellite (TESS), which will be launched in 2017.
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Mercury's transit will be too small to view using homemade pinhole cameras made to study Venus' passage. Telescopes outfitted with special filters will be able to spot the event.
NOTE: Never look directly at the sun without proper protective equipment. Doing so can cause serious eye damage or blindness. Check here to find out how to view the sun safely.
Fixing space