NASA image: Mercury transit
On May 9, 2016, Mercury passed directly between the sun and Earth.
This event – which happens about 13 times each century – is called a transit.
NASA's Solar Dynamics Observatory, or SDO, studies the sun 24/7 and captured the entire seven-and-a-half-hour event.
This composite image of Mercury's journey across the sun was created with visible-light images from the Helioseismic and Magnetic Imager on SDO.
Read more: Little Mercury a black dot as it crosses vast face of sun—http://phys.org/news/2016-05-mercury-black-dot-vast-sun.html