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Did you know you can use an inexpensive webcam to capture images of Jupiter and other objects in the night sky?

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A Light Year

Mercury is the closest planet to the Sun.


The Planet Mercury

Mercury is an extreme planet: the smallest, the densest, the one with the oldest surface, the one with the largest daily variations in surface temperature, and the least explored.

Mercury is the closest planet to our Sun. It is named for the ancient Roman god of trade and profit. Legend says Mercury's winged sandals gave him super speed. Mercury the planet is super fast, too. It zips around the Sun every 88 days - faster than any other planet. No wonder it got its name from the quickest of the ancient gods.

Mercury is just over a third as far from the sun as the Earth is; it is 0.387 A.U. from the sun (on average). Mercury's orbit is very eccentric; at aphelion (the point in the orbit farthest from the sun) Mercury is 70 million km from the sun, at perihelion Mercury is 46 million km from the sun.

There are no seasons on Mercury. Seasons are caused by the tilt of the axis relative to the planet's orbit. Since Mercury's axis is directly perpendicular to its motion (not tilted), it has no seasons.

Since the planet Mercury is close to the sun you will only see it near sunrise or just after sunset depending on which side of the sun the planet is on.
Like the Moon, the planet Mercury exhibits phases as seen from Earth. The first and last quarter phases occur at greatest elongation east and west, respectively, when Mercury's separation from the Sun ranges anywhere from 17.9° at perihelion to 27.8° at aphelion. At greatest elongation west, Mercury rises at its earliest before the Sun, and at greatest elongation east, it sets at its latest after the Sun.
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