Quelle est la planète la plus proche du soleil ?

La planète Mercure et le soleil

Our distance from the sun seems perfect, because the warmth it gives us is conducive to life. In fact, if we on Earth complain about heat waves, it’s a completely different atmosphere on Mercury, the closest planet to the sun.

Identified since the highest antiquity, by the Assyrians, already in the 20th century BC, Mercury is a very fast and very bright wandering star, visible to the naked eye before sunrise and after sunset. That’s why the Romans called it mercurythe name of messenger of the gods.

How far from the Sun is Mercury?

Of the eight main planets that make up our solar system, Mercury is closer to the sun. It is located 0.39 AU from the latter, which corresponds to 59 million kilometers middle distance

It is also the smallest of all the planets. Its diameter is only 4,879.4 kmThat’s it 3 times smaller than Earth.

His training dates from 4.5 billion years, or from the beginning of the solar system. Scientists believe that it is the result of the collision of a giant asteroid and a protoplanet.

During this event, solar radiation scattered Where destroy considerable amounts of material. This explains the thinness of the outer layer of the planet Simulations on the formation of planets have shown that it took 4 million years for 50% of these current particles turn to Mercury.

The planet Mercury in black and white

physical properties


Like everything telluric planetsMercury has three concentric solid and liquid envelopes including:

  • A norm metal core very dense, occupying almost 42% of its volume, 70% of its total mass. It represents 85% of the radius of the planet that corresponds approximately to 2025km.
  • A layer of molten mantle 200km within a rocky mantle 600km in fusion.
  • A solid shell of 35 to 54km covering the mantle.

Its surface is very similar to the far side of the moon. In fact, it’s riddled with craters resulting from violence meteor falls. Let us mention in particular Caloris Basinwhich measures approximately 1,300 km in diameter. It is the trace of a collision with an asteroid 150 km in size, 3.85 billion years ago.

It can be clearly noticed a large defect on its surface. Scientists believe that this is due to the cooling of its continental crust. Because of this, his lightning experienced a decrease of about 7 km following this phenomenon.

the planet mercury

atmosphere and climate

At first glance, Mercury appears dry and without an atmosphere, but it is not. The probes sent by the POT in particular, they were able to detect a modest proportion of hydrogen, helium, and oxygen. In addition, water vapor has also been included, as well as sodium, calcium and potassium. Which leads them to think that their atmosphere is in continuous renovation.

In fact, his original atmosphere it dispersed shortly after its formation. In addition, the heat, the low gravity of the planet and the greater action of the solar wind make Mercury impossible to maintain a meaningful environment. also justifies large temperature differences on its surface. At the zenith, when the sun is closest to perihelion, it can reach extremes of 420°C. On the contrary, it can reach -175°C in the shadow.

Furthermore, we find frozen at the poles at the bottom of craters 5 km deep and with a temperature of -200°C. This can be explained by the fact that these places are never exposed to the sun.

LOOK ALSO: How many planets are there in the solar system?

How to count the days on Mercury?


orbit of Mercury, in the form elliptical, is the most out of the way of the solar system. its distance from the sun varies by 40%. This figure is equivalent to 46 million km to 70 million km from the sun during its revolution.

She undertakes this journey during 88 earth days only. Thus, one year on Mercury thus corresponds to approximately 3 months on earth.

Instead, turns on itself more slowly due to its rotation period. Day on Mercury corresponds approximately to 59 earth days Initially approx. 2 months.


johannes kepler repeat the observations Tycho Brahe . Thus, it shows that the planet Mars crossed an elliptical orbit with variable speed.

he deduces that the distance from the sun can change. Because of this, the planets move faster closer to the Sun and slow down as they move further away.

In 1965 it was discovered a peculiarity on Mercury. Like what, approaching the perihelion, orbital speed is acceleratedthe planet at some point exceeds its speed of rotation and the sun rises there twice a day.

In other words, a full mercurial day it has a duration of two orbits around the sun (two Mercury years). Furthermore, she makes 3 turns on itself, that is, approximately 176 earth days.

Newton, discovered that the perihelion of Mercury move in time. According to him, it advances with an approximate term of 225,000 years and constantly changing position. This is due in large part to the influence of nearby planets : Jupiter, Venus, Earth.

That is Albert Einstein then who clarifies the reason for this phenomenon. In his theory, he explains that it is the colossal mass of the sun who bend spacetime, thus influencing the motion of Mercury’s perihelion. However, it was in 1915 that we were able to prove this postulate.

The transit of Mercury

Namely, that the plane of Mercury’s orbit is inclined at 7° over that of the earth. This is why this rare phenomenon occurs every 23 Mercury years on average. Thus, the transit of Mercury occurs when passes between the sun and the earth. It is visible as a black dot traversing the solar disk. The last transit of Mercury was on November 11, 2019 and the next one will be on November 13, 2032.

Space missions on Mercury

In 1974, the space probe MARINE 10 of the POT brings us the First images of the surface of Mercury. During its launch into orbit towards Venus, it is scheduled to pass close to Mercury every 2 Mercury years.

In 2004, a more sophisticated probe called DELIVERY COURIER is thrown for a orbit around mercury. However, due to the presence of the sun, regular orbit corrections are made for years before the goal is reached.

it’s just for 2011 that the probe finally reaches its destination. That said, it flew over the planet at a minimum altitude of 200 km and a maximum of 15,200 km. His mission lasts 4 years and ends in 2015.

In 2025, the probe bepicolombo of’ESA/JAXA released in October 2018 It should orbit Mercury. Its purpose is to study the planet and its magnetosphere for 2 years.

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