Monday, May 9, 2016

Rare Mercury Transit Wows Skywatchers

NASA's Solar Dynamics Observatory captures Mercury transit on May 9. Credit: NASA

Skywatchers across the globe have enjoyed an opportunity to see Mercury transit the Sun. Mercury's sojourn between Earth and our star lasted from 11:12 until 18:42 GMT. 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. As a result, Mercury transits occur only about 13 times a century. It was the third such pass of 14 this century; Mercury will not make another transit until 2019 and then 2032.

“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.

Open University's David Rothery said the celestial event did not present any novel scientific opportunities - but was special nonetheless.

"From this transit, we're unlikely to learn anything we don't already know," he told BBC Inside Science. "But what a wonderful event for showing people Mercury. It's a hard planet to see.

The entirety of Mercury's journey was viewable to the eastern U.S. and Canada, as well as most of western Europe and South America.

To catch a glimpse, viewers needed binoculars or telescopes with protective solar filters. Mercury's journey could also be seen via a livestream on NASA Television online as well as a website dedicated to the transit showing satellite imagery.


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