On Monday, May 9, 2016, people around the globe (with the exception of Australia and easternmost Asia) will be able to watch the transit of Mercury - an astronomical event when Mercury passes between the Earth and the Sun.
This rare event only happens around 13 times every 100 years. The last time it happened was in 2006 and the next time will be in 2019.
What time does the transit of Mercury start?
In the United States, the transit of Mercury begins on Monday, May 9, around 7:15 AM Eastern Daylight Time. Although the transit begins before sunrise on the U.S. west coast, it lasts for more than seven hours so everyone in the U.S. can watch the astronomical event.
How to watch the transit of Mercury
A telescope with a safe solar filter will be required to see the tiny disk of Mercury crawling across the face of the sun. Mercury is too small to be seen without magnification. Do not look at the Sun with the naked eye or unfiltered telescopes or binoculars.
Watch the transit of Mercury online
If you can't find access to a good telescope, NASA's Solar Dynamics Observatory will broadcast the event in real time on its website at: http://mercurytransit.gsfc.nasa.gov
Scientists will use the transit to study Mercury
NASA scientist Rosemary Killen and her colleagues plan to use the transit to study Mercury’s ultra-thin atmosphere or exosphere. The atoms in Mercury’s exosphere come from the surface of Mercury itself. They are blasted into space by solar radiation, solar wind bombardment and meteoroids. This gives Mercury a comet-like tail stretched out as long as 1.2 million miles. You cannot see this tail during the transit, however.
"When Mercury is in front of the sun, we can study the exosphere close to the planet. Sodium in the exosphere absorbs and re-emits a yellow-orange color from sunlight, and by measuring that absorption we can learn about the density of gas there,” said Killen.