Mercury: the planet you've never seen

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NASA’s MESSENGER spacecraft took this image of Mercury on September 28, 2009, on the way to its third flyby of the planet.  (Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington)
Amy Sayle, Morehead Planetarium
Science Center

So maybe YOU have seen the planet Mercury. But most people have not, or at least they have not realized they’ve seen it.

In an extremely unscientific email poll of fifteen of my friends and relatives, only two reported having knowingly seen Mercury in their lives. And as one said she spotted it at Halloween on Franklin Street, there is some ambiguity about whether she was referring to the actual planet or to a solar system costume.

The other thirteen responded with variations on "are you kidding" and "um, no."

Mercury is elusive. As the innermost planet, it never strays far from the Sun from our point of view on Earth. So you can forget about ever seeing Mercury conveniently placed high in the sky because the Sun would also be nearby, overpowering Mercury's much dimmer light.

Instead, your only chance to see Mercury with your unaided eye is when the planet is in the west soon after sunset, or in the east before sunrise. Right now are the best morning views of Mercury for 2009, but it will still be challenging.

First, you'll need to look quite low in the east. So your eastern horizon must be free of obstructions. (I know, good luck finding a tree-free view around here.)

Second, you'll need to choose a good time. Look too early and Mercury won't have risen yet. Look too late and the brightening sky will wash out Mercury from view.

I recommend trying 45 minutes before sunrise. For the Triangle area, that currently means looking about 6:30 a.m. Binoculars will help. But be careful not to aim them at the Sun after it rises unless you want to fry your eyes permanently.

If skies are clear (and the forecast does look fabulous for the Triangle area), try Thursday morning, October 8, when Mercury will appear very close in the sky to Saturn. Mercury, the brighter of the pair, will be within just 1/3 of a degree of Saturn. You'll notice Venus (the brightest of the three) a little higher than that.

Continue to watch these three planets each morning over the next week, and you’ll witness a slow dance. The morning of Oct. 13, it’s Saturn and Venus that appear as a close pair, with Mercury below.

If you decide to give up on Mercury, you can console yourself with the fact that not even the Hubble Space Telescope gets to see that planet—it's not allowed to point that close to the Sun. (But Mercury is hosting a visit from a spacecraft now.)
You can try for an easier-to-see planet at MPSC's next skywatching session. Weather permitting, we'll be at Jordan Lake's Ebenezer Church Recreation Area on Saturday, October 24, 7:30-9:30 pm. And so will Jupiter.

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