DETROIT – Perhaps you’ve already heard, but a somewhat uncommon astronomical event happens today, Monday, May 9. It’s called a transit of Mercury.
What’s a transit? For us here on Earth, a transit is when either the planet Mercury or the planet Venus moves right across the sun’s disk (only those two planets are applicable, because they are the only two closer to the sun than Earth and, thus, able to pass directly between the earth and the sun).
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Transits of Mercury aren’t very common, although they occur much more frequently than transits of Venus since Mercury is closer to the sun. The last transit of Mercury was on November 8, 2006, and the next two are November 11, 2019 and November 13, 2032.
Can we see it? The short answer is no -- not with the naked eye.
Mercury is a small planet, and even with a solar filter (which you need, obviously, because we can’t look at the sun with unprotected eyes), we need a telescope to see it cross the solar disk.
Transits of Venus ARE visible with the naked eye (again, with solar filters), and I vividly remember seeing the June 8, 2004 one with my solar filter…I was actually able to see Venus when it was in front of the sun. Oh, and by the way, the next Venus transit is Dec. 11, 2117, so don’t worry about trying to see that one. But Mercury is too small for us to see with the naked eye.
HOWEVER, there will be a number of telescopes around the world and in space observing this heavenly highlight, and you can watch images from NASA’s Solar Dynamics Observatory live as the transit happens here: mercurytransit.gsfc.nasa.gov.
The transit begins at 7:12 AM EDT, that’s when Mercury first moves onto the left edge of the solar disk, and ends at 2:42 PM EDT.
So, this is a long event (seven-and-a-half hours!), which means that you can periodically check in and see its progress at home or at work.