The planet Mercury is seen here in silhouette, lower third of image, as it transits across the face of the sun Monday, May 9, 2016, as viewed from Boyertown, Pennsylvania. Mercury passes between Earth and the sun only about 13 times a century, with the previous transit taking place in 2006. Images showed Mercury as a tiny black circle, smaller but darker than many sunspots, slowly traversing the Sun’s giant yellow disc.
Although Mercury zooms around the sun every 88 days, Earth, the sun and Mercury rarely align. And because Mercury orbits in a plane that is tilted from Earth’s orbit, it usually moves above or below our line of sight to the sun.
Transits provide a great opportunity to study the way planets and stars move in space – information that has been used throughout the ages to better understand the solar system and which still helps scientists today calibrate their instruments. Three of NASA’s solar telescopes will watch the transit for just that reason.
The May 9 Mercury transit occurred between about 7:12 a.m. and 2:42 p.m. EDT. “Astronomers get excited when any two things come close to each other in the heavens,” said Louis Mayo, program manager at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “This is a big deal for us.”
Mercury transits have been key to helping astronomers throughout history: In 1631, astronomers first observed a Mercury transit. Those observations allowed astronomers to measure the apparent size of Mercury’s disk, as well as help them estimate the distance from Earth to the sun.
“Back in 1631, astronomers were only doing visual observations on very small telescopes by today’s standards,” said Mayo.
Since then, technological advancements have allowed scientists to study the sun and planetary transits in greater detail. In return, transits allow us to test our spacecraft and instruments.
Scientists for the Solar and Heliospheric Observatory, or SOHO (jointly operated by NASA and ESA, the European Space Agency), and NASA’s Solar Dynamics Observatory, or SDO, worked in tandem to study the May 9 transit. The Hinode solar mission also observed the event. Hinode is a collaboration between the space agencies of Japan, the United States, the United Kingdom and Europe led by the Japan Aerospace Exploration Agency.
Photo Credit: (NASA/Bill Ingalls) – NASA/CINEWS