I've caught Mercury a few of times in recent days. Quite a feat when you consider that the tiny planet orbits the Sun at a breezy 112,000 mph. Of course, what I mean is I've 'caught' a glimpse of it above the southwestern horizon shortly after sunset. Even that is nothing to scoff at. Because the inner-most planet never gets far from the Sun it's notoriously hard to see. Viewing alternates from just before dawn to just after sunset. For reasons of orbit and inclination it has been relatively easy to spot recently. While it's starting to sink and fade you should still be able to see it for the next couple of days. Try looking low in the southwest about 6:00 pm. Binoculars, a clear sky and a little luck will help.
I think of our solar system as a big, diverse, raucous family. The Sun holds everybody together, but just barely. Many of the siblings have large families of their own, with Jupiter and Saturn having many dozens of moons between them. Mercury is definitely the runt of the litter, but it makes up in energy and eccentricity for what it lacks in size. Here's a brief portrait...
* Mercury is the smallest planet (remember that Pluto is no longer consider to be a planet). It's only a little bigger than our Moon and actually looks like the Moon with lots of craters. Both Jupiter and Saturn have moons larger than Mercury. To add insult to injury, Mercury is actually shrinking as it's iron core cools.
* Maybe there's a reason that Mercury and the Moon look alike. One theory posits that in the distant past Mercury collide with the Earth and the resulting debris came together to become our Moon.
* Mercury takes 88 days to orbit the Sun in a highly eccentric, egg shaped path where it's distance from the Sun varies between 29 million miles and 43 million miles.
* It rotates on it axis once every 58+ earth days but because of the speed of it's orbit a day/night cycle (what we would think of as a day) takes 176 of our days.
* Because it has almost no atmosphere to moderate temperature, the difference between its sun lite side (800 degrees F) and its dark side (-290 degrees F) is extreme. Of the planets, only Venus is hotter. Given enough time and foot dragging on climate change, maybe Earth can catch-up.
* While Mercury has no moons, it does have lots of craters and they have traditionally been named after famous (Earth based) writers and artists. Basho, Booticelli and Copland are all there.
* The Sun appears three times as large in Mercury's sky as it does here on Earth. If you love sunrises and sunsets Mercury may be your place. In an odd artifact of Mercury's rotation and orbit the Sun can be seen to rise, hesitate, and then sink back below the horizon before rising again. Sort of like me trying to get out of bed in the morning. The same phenomenon can sometimes be seen at sunset.
Forget about booking your flight to visit this strange world. It's really quite hard to get too with only a couple of spacecraft having made the journey. I believe there's one on the way now but not due to arrive for several years. In the meantime try for an evening sighting on the next clear night. Just remember to bundle up because January is finally acting like...well, like January. It's cold out there.
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