Mercury is the first planet from the Sun. That, of course, is way too simple an answer. To find the location of Mercury in the sky here on Earth, you need a flat area with a clear view to the horizon. You need a view to the east if you want to find Mercury in the morning before the Sun rises or one to the west if you want to find Mercury in the evening, after the Sun clears the horizon.
In the morning, Mercury will rise in the eastern skies before the Sun. When Mercury is trailing the Sun, you can look to the western sky. Mercury will be a bright star-like object then. Actually, it will be one of the first stars that you see in the night sky. You must work quickly though; it sets not long after the Sun. To place in a more complete way of speaking: Mercury is always within 28 degrees of the Sun. Temperate latitudes can only observe it during twilight and only when it is near elongation. That is from January to April for evening observation in the northern hemisphere and from July to October for morning observation. People in the southern hemisphere should reverse these time frames. Look about ten degrees above the Sun, forty-five minutes before sunrise/set, low in the horizon. Mercury is white but may look pink in the evening. When observed at dawn or dusk, Mercury is so low on the horizon that the light must pass through 10 times the amount of atmosphere than it would if it were directly overhead. While it is fun to look with the unaided eye, it may be advisable to use a small telescope. Mercury is seen as a small disc between 5 and 15 arcseconds across. The disc reveals phases with a superior conjunction and an inferior conjunction.
Mercury has an extremely eccentric orbit. While it orbits as close as 46 million km from the Sun, it also range out to 69,816,900 km. It only takes Mercury 88 Earth days to orbit the Sun and it rotates three time every two orbits for an orbital resonance of 3:2.
the location of Mercury is easy to find, but the planet is the devil to observe from Earth. That is why there is so little known about it.
We have written many stories about Mercury here on Universe Today. Here’s an article about a the discovery that Mercury’s core is liquid. And how Mercury is actually less like the Moon than previously believed.
If you’d like more information on Mercury, check out NASA’s Solar System Exploration Guide, and here’s a link to NASA’s MESSENGER Misson Page.
We have also recorded a whole episode of Astronomy Cast that’s just about planet Mercury. Listen to it here, Episode 49: Mercury.
Reference:
NASA Astronomy Photo of the Day
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