Mercury completes its transit across the Sun

On Monday May 9, 2016, Mercury completed a transit across the sun, passing between both Earth and our star. This type of journey only happens approximately 13 times in a century, and the last time it occurred was in 2006.

When a planet passes in front of its star, the event is known as a transit. In the case of our solar system, the only two planets we will ever see make this type of dash across the sun’s disk are Mercury and Venus as they are the closest to the sun.

During the transit, Mercury appeared as a small black dot crossing the edge of the sun from 7:12 a.m., reaching mid-point at approximately 10:47 a.m., and finishing its journey at 2:42 p.m. The entire seven and a half hour path across the sun was visible anywhere in the Eastern United States with magnification and proper solar filters; those in the West were able to observe the transit in progress after sunrise.

NASA’s Solar Dynamics Observatory team captured the entire time lapse. It used its Kepler space telescope, a device that watches for the slight dimming of the light of stars, which reveals an exoplanet has passed in front and blocked a tiny amount of starlight.

The Mercury transit can be used to study the planet’s exosphere, a very thin atmosphere that fizzes into space. Any sunlight that passes through the exosphere is encoded with spectroscopic data that can be used to work out the nature of the environment surrounding Mercury.

Via NASA