Planetary Science
Planet Mercury
Planet Uranus

What is the planet Mercury?

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2009-01-13 03:45:49

Mercury is the innermost and smallest planet in the solar

system, orbiting the Sun once every 88 days. It ranges in

brightness from about −2.0 to 5.5 in apparent magnitude, but is not

easily seen as its greatest angular separation from the Sun

(greatest elongation) is only 28.3°. It can only be seen in morning

or evening twilight. Comparatively little is known about the

planet: the only spacecraft to approach Mercury was Mariner 10 from

1974 to 1975, which mapped only 40%–45% of the planet’s surface.

Physically, Mercury is similar in appearance to the Moon as it is

heavily cratered. It has no natural satellites and no substantial

atmosphere. The planet has a large iron core which generates a

magnetic field about 0.1% as strong as that of the Earth[1].

Surface temperatures on Mercury range from about 90 to 700 K (−180

to 430°C, −292 to 806°F), with the subsolar point being the hottest

and the bottoms of craters near the poles being the coldest. The

Romans named the planet after the fleet-footed messenger god

Mercury, probably for its fast apparent motion in the twilight sky.

The astronomical symbol for Mercury, displayed at the top of the

infobox, is a stylized version of the god’s head and winged hat

atop his caduceus, an ancient astrological symbol. The Greeks

called it Στίλβων Stilbon (“the gleaming”) and Hermaon. Before the

5th century BC, Greek astronomers believed the planet to be two

separate objects: one visible only at sunrise, the other only at

sunset. In India, the planet was named Budha (बुध), after the son

of Chandra (the Moon). The Chinese, Korean, Japanese, and

Vietnamese cultures refer to the planet as the water star , based

on the Five Elements. The Hebrews named it Kokhav Hamah (כוכב חמה),

“the star of the hot one” (“the hot one” being the Sun). Mercury is

smaller than several of the natural satellites or moons in our

solar system. MERCURY - is the closest planet to the Sun and so is

also the fastest moving (that gravity!), orbiting our star four

times faster than the Earth. Because it is so close to the Sun the

intense heat doesn't allow any atmosphere to exist, so the daytime

temperatures can reach 400°C whilst at night the thermometer

plunges to -170°C. Diameter: 4,878 kilometres Distance from the

Sun: 57.9 million kilometres Orbits the Sun in (one Mercurian

year): 88 days Rotates in (one day): 58 days 15 hours 30 minutes

Rank: 2nd smallest planet - 8th in size Looks: Like the Moon - lots

of craters OBSERVING MERCURY: Mercury is quite a small planet and

the word 'elusive' is often used in terms of trying to find it.

This is because it stays close to the Sun and so it never appears

far above the horizon. Even some astronomers have not seen

Mercury!, but if you know where and exactly when to look, Mercury

can be fairly easily found. A small telescope will show the phases,

but not any details on Mercury's scorching surface. Due to it's

tilted orbit the best times to see Mercury are the evening skies of

spring or the morning skies during autumn.


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