Mercury is the closest planet to the sun. The
orbit, or path, it takes around the sun is not in a circle like Earth.
The path it takes is called an ellipse, which is like a circle that
has been stretched out. For this reason, the distance from Mercury to
the Sun varies from about 27 million miles at its closest, to about 41
million miles at its furthest.
Mercury races around the Sun faster than any other planet. A Mercurian
year (the time it takes for the planet to go once around the Sun, is
only 88 days, while our year on Earth is 365 days. Mercury does not
spin as fast as Earth, though, so a Mercurian day (the time it takes a
planet to rotate once) is 59 Earth days!
- Can I See It?
Yes you can, and you won't need a telescope, but Mercury is normally
visible for a few days only three or four times a year. Because of its
closeness to the Sun, Mercury is normally hidden by sunlight. When the
planet is visible, you either have to get up before sunrise or be
watching closely just after sunset. Mercury never gets very far above
the horizon, so you will also need a place where can see clearly to
either the east or west. Check the sky maps here at Astronomy for
Kids. If Mercury is going to be visible, we will tell you when and how
to see it.
How Big Is It?
Mercury is the second smallest planet in the solar system. Pluto is
the only planet that is smaller. Earth is about 7,200 miles in
diameter, while tiny Mercury is less than half that size at about
3,000 miles in diameter. Put another way, if Earth was the size of a
baseball, Mercury would be a little smaller than a ping-pong ball.
Mercury is so small that Ganymede, one of Jupiter's moons, and Titan,
one of Saturn's moons, are both larger.
How Did It Get Its Name?
Mercury is named for the Roman god of commerce and thievery. It may
have gotten this name because of the way it quickly appears and
disappears from our view.
What Is It Made Of?
Mercury is one of the rocky planets of the solar system, along with
Earth and Venus. Mercury is made up mostly of iron, with a thin rocky
layer on the planet surface.
What's It Like on The Surface?
On thje surface of Mercury, you will see that there are many craters on its surface.
The planet has been hit many, many times through the years by
asteroids and other objects. These impacts are responsible for all the
craters on the surface. Earth probably had this many craters at one
time, but our weather has worn the down over the years.
The weather on Mercury varies from extremely hot to extremely cold. If
you were on the side of the planet facing towards the Sun, you would
quickly melt, as the temperature would be around 700 degrees! The
"daytime" temperature on Mercury varies, depending on how
close it is to the Sun. At the other extreme, the temperature on the
"nighttime" side of the planet (the side away from the Sun)
can be over 300 degrees below zero! Mercury is not a very pleasant
place.
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