History of Mercury

Mercury is the smallest planet in the solar system and the closest to the Sun. Planet name is taken from the name of the messenger god of ancient Rome. He was given the name because of its motion in the sky very quickly. From Earth, Mercury can only be observed visually at a maximum distance of 28.3 ° from the Sun. That is, the planet is visible in the eastern sky just before sunrise or after sunset in the west. With such a small angle range, we only have a maximum of 1 hour 53 minutes to observe the planet, which is when Mercury reaches maximum elongation. So, we will never be able to see Mercury zenith (see picture below). The planet is experiencing two inferior conjunctions in the intervening 116 days, so the appearance alternately in the east and west occurred within an interval of about 60 days. Since the emergence of the alternate planet that was identified by the ancient Greeks as 2 different objects. At that time, Mercury appears in the eastern sky and was given the name Apollo appears in the western sky was named Hermes.

Uniqueness Mercury

If we are in Mercury, we can see the sun moving retrograde in the sky. At one location, after rising in the east and before crossing the meridian, the Sun would move slightly backwards, stopped, then moved back to the west to sunset. Please see for yourself by using a sky simulation program (eg Stellarium). The cause of the Sun's retrograde motion is due at the time of the revolution Mercury's angular speed becomes equal to the rate of rotation angle.

Mercury around the Sun during the 88 days of Earth, while the rotation period is 58.7 Earth days. We can see that the ratio of the period of revolution and rotation is 2/3. That is, the planet of revolution completed 2 times in the same time with 3 times rotation. Even so, Mercury takes 176 Earth days to experience all day and night. Means a day on Mercury is much longer than one year.

Physical Characteristics

Planet rock is only about 4800 km in diameter. This size is smaller than Ganymede and Titan (2 largest satellite in the solar system) but Mercury is still more massive of the two. With a density of 5.43 g / cm ^ 3, Mercury became the second highest density of objects in the solar system after Earth. The core of this planet are known to be dominant relative to its size, reaching 42% of the total volume with a radius of 1800 km.

Eccentricity of the orbit of Mercury is the greatest of all the planets, which is 0.21. The distance of the sun between 46 million miles to 70 million miles. While the distance from Earth varies between 77 million km and 222 million km and kecerlangannya ranged between -2.3 (brighter than the star Sirius) and 5.7.

Mercury orbit inclination to the ecliptic is 7 degrees. The tilt angle of the axis of rotation axis of revolution is close to zero, about 0.027 degrees. Still smaller than Jupiter which was 3.1 degrees. With such a small angle, no 4 seasons in the northern and southern hemisphere of Mercury. The temperature at the surface varies between 80-700 K.

Flight Mission to Mercury

Mercury is one of the objects that are difficult to observe, so not much information to be gained from it. Even the new planet's rotation period is well known in 1965 after Mercury observed by radar. Shipping a vehicle to examine Mercury up close was not easy. Its position close to the sun, lack of atmosphere, and the difference in the rate of orbit are some things difficult. As a result, until now there were only two successful missions to observe Mercury, the Mariner 10 and Messenger.

Mariner 10 spacecraft was launched on 3 November 1973. Departure process that utilizes the planet Venus (the "slingshot" gravity) is the first carried out in the history of space flight. When passed near Venus, the spacecraft took footage of the planet's ultraviolet photography. Although Venus has been observed with ground-based telescopes before, still photos provided Mariner 10 Venus is inviting admiration researchers.

This vehicle has been providing exceptional knowledge of Mercury's surface and detect the magnetic field of Mercury. One thing that was surprising to the researchers this planet has a slow rotation. Finally, in 1975 Mariner 10 was defunct after its fuel runs out and the contact stopped.