Planet Mercury
Scientists were late in discovering the planet Mercury, due to its location, as it is close to the western horizon, and therefore the atmosphere works to absorb the light it emits, in addition to the fact that the twilight that appears during sunset contributes to hiding it, which makes it difficult to monitor. However, it is noteworthy that the first information obtained by astronomers about this planet was in the year 1974 AD, when the American spacecraft Mariner headed to its surface to study it. In this article, we will introduce you to a set of information about the planet Mercury.
Movement of Mercury in the solar system
The distance between the planet Mercury and the sun is about 47.6 km, and therefore it is considered the closest planet in the solar system to the sun. Mercury's sidereal day is estimated at 58.65 Earth days, while its sidereal year is equal to 87.97 Earth days. This means that one day on this planet is equivalent to a third of a year. The transit of the planet Mercury occurs between the Sun and the Earth, and is in the form of a small black dot. It is noteworthy that scientists have noticed that each time the transit time is 43 seconds ahead of the previous time, but there has been no logical explanation until now. The gravity on this planet is 0.378 of Earth's gravity, and its inclination from the ecliptic is estimated at about seven degrees.
Mercury observation
The apparent magnitude of Mercury ranges from -2.3 brighter than Sirius to +5.7, and the maximum apparent magnitude is when it is close to the sun in the sky. Observing Mercury is complicated because it is close to the Sun, making it difficult to observe due to its glare. It can be seen for a short time at dawn and dusk, and the Hubble Space Observatory has not been able to watch it at all yet, due to precautions that prevent it from directing it close to the Sun. Mercury can be seen from the southern hemisphere more easily than from the northern hemisphere.
Mercury among the ancients
In the time of Hesiod, the Greeks knew about the planet Mercury, and they called it “Stilbone” (Greek: Στίλβων) and “Hermione” (Greek: Ἑρμάων), thinking that it was two separate celestial bodies. Later they gave him the name Apollo when he is visible at dawn, and Hermes when he is visible at dusk. In the fourth century BC, Greek astronomers realized that the two names belong to the same body. The Romans later gave the name “Mercury” (in Latin: Mercurius) to the planet, which corresponds to the Greek god Hermes, because it moves in the sky faster than any other planet, as does the aforementioned god according to their beliefs. The Roman-Egyptian scientist Claudius Ptolemy wrote about the transit of Mercury in front of the Sun. He suggested that the transit is not observed because of the small size of Mercury and that this transit is infrequent.
Mercury was known to the ancient Chinese as “Xin Xing” (Chinese: 辰星), and it is linked to the north direction and is in the water phase according to the principle of the five elements (Chinese: 五行), which the Chinese believed made up the world.
According to Hindu mythology, the name Buddha was used for him, as is the god Odin according to Scandinavian mythology, while the Mayans represented Mercury with an owl and sometimes with four owls, two of which were for the morning appearance and two for the night appearance, and all of them served as messengers to the underworld. In the fifth century, an Indian astronomical text called Suraiya Siddhanta determined the diameter of the planet Mercury at three thousand and eight miles, that is, with an error less than 1% than the true value of 3,032 miles.
The Arabs used to call this planet Mercury, in reference to “Tarid” and “Mercury,” meaning the one who continues its journey. This symbolizes the great speed with which the planet revolves around the sun. As for Muslim astronomers, in the eleventh century AD, the Andalusian astronomer Ibrahim bin Yahya Al-Zarqali described the orbit of Mercury as elliptical and resembling an egg. In the twelfth century, the scientist Ibn Baja observed two dark spots on the surface of the sun, and Qutb al-Din al-Shirazi later suggested that these two spots were nothing but the transit of Mercury and Venus. That was in the thirteenth century.
Surface geology of Mercury
The surface of Mercury is spherical and very similar to the surface of Earth's moon, and dark spots called lunar seas appear on it, similar to what is on the moon, formed as a result of volcanic activity, and large craters, which indicate its geological activity billions of years ago. Since information about Mercury's terrain is derived from the Mariner 10 flight and ground observations, knowledge about its nature is less than the rest of the planets. Currently, the information obtained through MESSENGER data increases human knowledge of this planet. For example, the discovery of an unusual impact crater with radioactivity that scientists released It has the name “Spider”.
The characteristics of the albedo indicate the presence of regions with different reflectivity, and thus Mercury has different terrains of mountains, plains, valleys, hills and slopes. Mercury was subjected to meteorite and asteroid bombardment shortly after its formation 4.6 billion years ago, and it may have been exposed during a later period to what is called late heavy bombardment 3.8 billion years ago. During this period, many impact craters were formed and collisions occurred over its entire surface, and with the passage of some time the planet became active. Volcanically, some different terrains were formed. The antiquity of impact craters indicates the internal activity of the planet due to monitoring the different terrain, including mountain ranges, plains, and valleys that intersect the impact craters. Among the most famous features of the surface are two hot areas in which the temperature reaches the highest value. In one of them is located the most famous crater, which is the “Caloris Basin”, which is estimated to be four thousand million years old. It is believed that the reason for its formation is a huge collision that occurred on the surface of the planet in this region, and it was called by this name to mean Temperature, Calorie, as the average temperature reaches a maximum of 430 degrees Celsius when this basin is at the bottom and directly facing the sun. As for the directly opposite side of the basin on the other side, it is an area with irregular elevations and terrain that covers 360,000 square kilometers of the planet’s area and consists of valleys, hills, and mountains that reach a height of two kilometers. It is called the Weird Terrain, which is believed to be caused by waves resulting from... The impact caused by Caloris Crater is the reason for the formation of this region on the opposite side.
Climate on Mercury
The average temperature of Mercury's exposed side to the Sun is 442.5 K, despite the large discrepancy between the lower and upper temperatures, which range between 100 K and 700 K, due to the almost absence of an atmosphere and the sharp drop in temperatures between the equator and the poles. The temperature in the area exposed to the sun reaches 700 K during perihelion and drops to 550 K during aphelion, while the dark side has an average temperature of about 110 K. The intensity of the solar radiation on Mercury ranges between 4.59 and 19.61 times the solar radiation constant of 1.370 W/m2.
No moons for Mercury
Mercury has no characteristic moons, and it and Venus are the as it were planets without a moon framework.
To reply the cause of the irregularity in these two planets, a hypothesis was proposed within the mid-1960s, that Mercury was a moon of Venus and was able to elude its circle around Venus.
Numerous computer reenactment tests are presently being conducted to confirm this speculation and the reasons for the conceivable elude.
As in case the activity of the tidal drive between the two planets had caused this elude, or since the circles of the two planets were distant separated from each other.
Mercury's atmosphere
Mercury is a very small planet, and because of this, its mass and therefore its gravity are far too small to form a significant atmosphere, in addition to its proximity to the sun and its extreme heat, which make its atmosphere escape quickly and easily. However, it has a thin “outer shell,” consisting of: hydrogen, helium, oxygen, sodium, calcium, potassium, and some other elements.[89] The “exosphere” or “exosphere” is the upper layer of the atmosphere, but its scarcity on Mercury and the lack of other layers makes astronomers consider that it does not have an important atmosphere compared to other planets.
But the atoms of its exosphere are not stable, they are constantly escaping its gravity (mainly due to the solar wind), and then are replaced by others from various sources such as: the solar wind itself, ash and debris ejected from the surface due to collisions. In 2008, water vapor was discovered in Mercury's atmosphere, and it is believed to have formed as a result of the meeting of hydrogen and oxygen atoms in the atmosphere. Hydrogen and helium atoms may come into its atmosphere from the solar wind, where Mercury captures them temporarily before escaping back into space due to its weak gravity. There are no clouds, winds, or any other weather phenomena on Mercury.
In its first days after its birth 4.6 billion years ago, Mercury had an atmosphere, but shortly after its birth its atmosphere eroded and disappeared due to the strong solar winds blowing on it due to its close proximity to the sun. The Mariner 10 spacecraft detected trace amounts of helium 1,000 km above Mercury's surface during its flyby in 1974 and 1975. Mariner 10 data are also the first to prove the existence of Mercury's thin outer shell.
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