Mercury
Messenger Of The Gods

mercury

This barren looking rock is named Mercury... in honor of the fleet-footed messenger of the gods who is also known as Hermes.

This planet of incredible speed and swiftness, because of it's closeness to the sun,  is able to complete a year before it completes a day.

The planet is so fast it circles the sun in about 88 Earth days, sunrise to sunrise  though is about 176 Earth days.

Unfortunately, this closeness is what makes viewing it so hard. Viewed from Earth you are always looking towards the sun and it tends to get lost in the glare.

Because of this the planet is only visible for a short time either just before sunrise or just after sunset, depending on where it is in its orbit.

The best time to hunt for this speedster is when it is near greatest elongation from the Sun, when the distance between the two in our sky is farthest. Greatest elongations occur often. There are two kinds of Elongations: The Eastern Elongation occurs when the planet is in the evening sky and the Western Elongation Occurs when a planet is in the morning sky.

When a planet is at Elongation, it is furthest from the Sun as viewed from Earth, so it's view is best at that point.

mercury as half moon

The spring and early summer prove to be the best times of year for observers in the Northern Hemisphere during evening elongations, while the fall and early winter are best in the early morning.

The exact opposite is true from the Southern Hemisphere. Even then, binoculars can help isolate the planet.

In a telescope, Mercury appears as a tiny gray disk. Like Venus and the Moon,it goes through different phases.

The apparent size of its disk varies with phase. Because the planet hugs so close to the horizon, the disk usually shimmers from atmospheric turbulence.

A better image can be obtained when the planet is higher in the sky, during evening or morning twilight, even though the contrast won't be as good.

It is at its brightest as seen from Earth when it is at a gibbous phase. This is between either quarter phase and full.

Although the planet is further away from Earth when it is gibbous than when it is a crescent, the greater illuminated area visible more than compensates for the greater distance.

The opposite is true for Venus which appears brightest when it is a thin crescent. Because it is much closer to Earth than when gibbous.

Because these inner planets are inside the Earth's orbit their positions as viewed from the Earth are never very far from the position of the Sun.

Because Mercury is an inner planet it will never resolve to a whole disk in a telescope. When it is in the position to be "Full" it is located on the far side of the Sun relative to the Earth.

When viewing, the planet will appear as a crescent or gibbous shape. It will appear pinkish with gray markings.

The apparent magnitude varies between about −2.3, which is brighter than Sirius, and 5.7.

rocky mercury

Very similar in appearance to the Moon: it is heavily cratered with regions of smooth plains, has no natural satellites or moons of its own and no substantial atmosphere.

Greek astronomers believed the planet to be two separate objects: one visible only at sunrise, which they called Apollo; the other visible only at sunset, which they called Hermes. They realized eventually that it was after all the same one just moving so fast in its orbit it seemed to be two separate objects.

Mercury is only about one-third the size of the Earth. It is smaller than any other planet, and two of the solar system's moons.

Mercury is the second most dense planet after Earth.

› Mercury
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