The orbital period of Mercury's moon. Mercury is the planet closest to the sun

12.10.2019

Compression < 0,0006 Equatorial radius 2439.7 km Medium radius 2439.7 ± 1.0 km Circumference 15329.1 km Surface area 7.48×10 7 km²
0.147 Earth Volume 6.08272×10 10 km³
0.056 Earth Weight 3.3022×10 23 kg
0.055 Earth Average density 5.427 g/cm³
0.984 Earth Acceleration of free fall at the equator 3.7 m/s²
0,38 Second space velocity 4.25 km/s Rotation speed (at the equator) 10.892 km/h Rotation period 58.646 days (1407.5 hours) Tilt axis of rotation 0.01° Right ascension at the north pole 18 h 44 min 2 s
281.01° Declination at the north pole 61.45° Albedo 0.119 (Bond)
0.106 (geom. albedo) Atmosphere Composition of the atmosphere 31.7% potassium
24.9% sodium
9.5%, A. oxygen
7.0% argon
5.9% helium
5.6%, M. oxygen
5.2% nitrogen
3.6% carbon dioxide
3.4% water
3.2% hydrogen

Mercury in natural color (Image Mariner 10)

Mercury- the closest planet to the Sun in the solar system, revolves around the Sun in 88 Earth days. Mercury is an inner planet because its orbit is closer to the Sun than the main asteroid belt. After depriving Pluto of the status of a planet in 2006, Mercury passed the title of the smallest planet in the solar system. Mercury's apparent magnitude ranges from −2.0 to 5.5, but is not easy to see due to its very small angular distance from the Sun (maximum 28.3°). At high latitudes, the planet can never be seen in the dark night sky: Mercury is always hidden in the morning or evening dawn. The optimal time for observing the planet is morning or evening twilight during periods of its elongations (periods of maximum removal of Mercury from the Sun in the sky, occurring several times a year).

It is convenient to observe Mercury at low latitudes and near the equator: this is due to the fact that the duration of twilight is the shortest there. In middle latitudes, finding Mercury is much more difficult and only during the period of the best elongations, and in high latitudes it is impossible at all.

Relatively little is known about the planet. The Mariner-10 apparatus, which studied Mercury in -1975, managed to map only 40-45% of the surface. In January 2008, the interplanetary station MESSENGER flew past Mercury, which will enter orbit around the planet in 2011.

In terms of its physical characteristics, Mercury resembles the Moon and is heavily cratered. The planet has no natural satellites, but has a very rarefied atmosphere. The planet has a large iron core, which is the source of the magnetic field in its totality, which is 0.1 of the earth's. Mercury's core makes up 70 percent of the planet's total volume. The temperature on the surface of Mercury ranges from 90 to 700 (from −180 to +430 ° C). The solar side heats up much more than the polar regions and the far side of the planet.

Despite the smaller radius, Mercury still surpasses in mass such satellites of the giant planets as Ganymede and Titan.

The astronomical symbol of Mercury is a stylized depiction of the winged helmet of the god Mercury with his caduceus.

History and name

The oldest evidence for the observation of Mercury can be found in Sumerian cuneiform texts dating back to the third millennium BC. e. The planet is named after the god of the Roman pantheon Mercury, an analogue of the Greek Hermes and Babylonian Naboo. The ancient Greeks of the time of Hesiod called Mercury "Στίλβων" (Stilbon, Brilliant). Until the 5th century BC e. the Greeks believed that Mercury, visible in the evening and morning sky, are two different objects. In ancient India, Mercury was called Buddha(बुध) and Roginea. In Chinese, Japanese, Vietnamese and Korean, Mercury is called water star(水星) (in accordance with the concept of the "Five Elements". In Hebrew, the name of Mercury sounds like "Kokhav Hama" (כוכב חמה) ("Solar Planet").

planet movement

Mercury moves around the Sun in a rather strongly elongated elliptical orbit (eccentricity 0.205) at an average distance of 57.91 million km (0.387 AU). At perihelion, Mercury is 45.9 million km from the Sun (0.3 AU), at aphelion - 69.7 million km (0.46 AU) At perihelion, Mercury is more than one and a half times closer to the Sun than at aphelion. The inclination of the orbit to the plane of the ecliptic is 7°. Mercury spends 87.97 days per orbit. The average speed of the planet in orbit is 48 km/s.

For a long time it was believed that Mercury is constantly facing the Sun with the same side, and one revolution around its axis takes the same 87.97 days. Observations of detail on the surface of Mercury, made at the limit of resolution, did not seem to contradict this. This misconception was due to the fact that the most favorable conditions for observing Mercury are repeated through a triple synodic period, that is, 348 Earth days, which is approximately equal to six times the rotation period of Mercury (352 days), therefore, approximately the same surface area was observed at different times planets. On the other hand, some astronomers believed that the Mercury day is approximately equal to the Earth day. The truth was revealed only in the mid-1960s, when the radar of Mercury was carried out.

It turned out that the Mercury sidereal day is equal to 58.65 Earth days, that is, 2/3 of the Mercury year. Such a commensurability of the periods of rotation and revolution of Mercury is a unique phenomenon for the solar system. This is presumably due to the fact that the tidal action of the Sun took away the angular momentum and slowed down the rotation, which was initially faster, until the two periods were connected by an integer ratio. As a result, in one Mercury year, Mercury has time to rotate around its axis by one and a half turns. That is, if at the moment Mercury passes perihelion, a certain point of its surface faces exactly the Sun, then during the next passage of perihelion, exactly the opposite point of the surface will face the Sun, and after another Mercury year, the Sun will again return to the zenith over the first point. As a result, a solar day on Mercury lasts two Mercury years or three Mercury sidereal days.

As a result of such a movement of the planet, “hot longitudes” can be distinguished on it - two opposite meridians, which alternately face the Sun during the passage of perihelion by Mercury, and on which, because of this, it is especially hot even by Mercury standards.

The combination of the movements of the planet gives rise to another unique phenomenon. The speed of rotation of the planet around its axis is practically constant, while the speed of orbital motion is constantly changing. In the segment of the orbit near the perihelion, for about 8 days, the speed of orbital motion exceeds the speed of rotational motion. As a result, the Sun in the sky of Mercury stops, and begins to move in the opposite direction - from west to east. This effect is sometimes called the Joshua effect, after the protagonist of the Book of Joshua from the Bible, who stopped the movement of the Sun (Joshua, x, 12-13). For an observer at longitudes 90° away from the "hot longitudes", the Sun rises (or sets) twice.

It is also interesting that, although Mars and Venus are the closest orbits to Earth, it is Mercury that is the closest planet to Earth most of the time than any other (because others move away to a greater extent without being so “tied” to the Sun).

physical characteristics

Comparative sizes of Mercury, Venus, Earth and Mars

Mercury is the smallest terrestrial planet. Its radius is only 2439.7 ± 1.0 km, smaller than that of Jupiter's moon Ganymede and Saturn's moon Titan. The mass of the planet is 3.3 × 10 23 kg. The average density of Mercury is quite high - 5.43 g / cm³, which is only slightly less than the density of the Earth. Considering that the Earth is larger in size, the value of the density of Mercury indicates an increased content of metals in its bowels. The free fall acceleration on Mercury is 3.70 m/s². The second space velocity is 4.3 km/s.

Kuiper Crater (just below center). MESSENGER image

One of the most noticeable details of the surface of Mercury is the Heat Plain (lat. Caloris Planitia). This crater got its name because it is located near one of the "hot longitudes". Its diameter is about 1300 km. Probably, the body, upon impact of which the crater was formed, had a diameter of at least 100 km. The impact was so strong that seismic waves, having passed the entire planet and focused at the opposite point of the surface, led to the formation of a kind of intersected "chaotic" landscape here.

Atmosphere and physical fields

During the flight of the Mariner-10 spacecraft past Mercury, it was established that the planet has an extremely rarefied atmosphere, the pressure of which is 5 × 10 11 times less than the pressure earth's atmosphere. Under such conditions, atoms collide with the surface of the planet more often than with each other. It consists of atoms captured from the solar wind or knocked out by the solar wind from the surface - helium, sodium, oxygen, potassium, argon, hydrogen. The average lifetime of an atom in the atmosphere is about 200 days.

Mercury has a magnetic field, the intensity of which is 300 times less than the intensity magnetic field Earth. The magnetic field of Mercury has a dipole structure and is highly symmetrical, and its axis deviates by only 2 degrees from the axis of rotation of the planet, which imposes a significant limitation on the range of theories explaining its origin.

Research

An image of a portion of the surface of Mercury taken by the MESSENGER spacecraft

Mercury is the least explored terrestrial planet. Only two vehicles were sent for his research. The first was Mariner 10, which flew past Mercury three times in -1975; the maximum approach was 320 km. As a result, several thousand images were obtained, covering approximately 45% of the planet's surface. Further studies from Earth showed the possibility of the existence of water ice in polar craters.

Mercury in art

In Boris Lyapunov's sci-fi story "Nearest to the Sun" (1956) Soviet cosmonauts landed on Mercury and Venus for the first time to study them.
In Isaac Asimov's story "The Big Sun of Mercury" (a series about Lucky Starr), the action takes place on Mercury.
Isaac Asimov's stories Runaround and The Dying Night, written in 1941 and 1956 respectively, describe Mercury facing the Sun on one side. At the same time, in the second story, the key to the detective story is built on this fact.
In the science fiction novel The Flight of the Earth by Francis Karsak, along with the main plot, a scientific station for studying the Sun is described, located at the North Pole of Mercury. Scientists live on a base located in the eternal shadow of deep craters, and observations are made from giant towers constantly illuminated by the luminary.
In Alan Nurse's science fiction novel Across the Sunny Side, the main characters cross the side of Mercury facing the Sun. The story was written in accordance with the scientific views of its time, when it was assumed that Mercury was constantly facing the Sun on one side.
In the anime animated series Sailor Moon, the planet is personified by the warrior girl Sailor Mercury, she is Ami Mitsuno. Her attack lies in the power of water and ice.
In Clifford Simak's science fiction story "Once Upon a Time on Mercury", the main field of action is Mercury, and the energy form of life on it - balls, surpasses humanity by millions of years of development, having long passed the stage of civilization.

Notes

Literature

Bronstein V. Mercury is the closest to the Sun // Aksenova M.D. Encyclopedia for children. T. 8. Astronomy - M.: Avanta +, 1997. - S. 512-515. - ISBN 5-89501-008-3
Xanfomality L.V. Unknown Mercury // In the world of science. - 2008. - № 2.

Links

MESSENGER mission website
- Pictures of Mercury taken by Messenger
BepiColombo mission section on the JAXA website
A. Levin. Iron Planet Popular Mechanics #7, 2008
"The closest" Lenta.ru, October 5, 2009, photographs of Mercury taken by "Messenger"
“New images of Mercury published” Lenta.ru, November 4, 2009, about the approach on the night of September 29 to 30, 2009 of Messenger and Mercury

The first photo of MESSENGER from Mercury's orbit, with the bright Debussy crater visible at upper right. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington.

Characteristics of Mercury

Weight: 0.3302 x 1024 kg
Volume: 6.083 x 10 10 km 3
Average radius: 2439.7 km
Average diameter: 4879.4 km
Density: 5.427 g/cm3
Escape velocity (second escape velocity): 4.3 km/s
Surface Gravity: 3.7 m/s2
Optical magnitude: -0.42
Natural satellites: 0
Rings? - Not
Major axis: 57,910,000 km
Orbital period: 87.969 days
Perihelion: 46,000,000 km
Aphelion: 69,820,000 km
Average orbital speed: 47.87 km/s
Maximum orbital speed: 58.98 km/s
Minimum orbital speed: 38.86 km/s
Orbital inclination: 7.00°
Orbital eccentricity: 0.2056
Sidereal rotation period: 1407.6 hours
Day length: 4222.6 hours
Discovery: Known since prehistoric times
Minimum distance from Earth: 77,300,000 km
Maximum distance from Earth: 221,900,000 km
Maximum apparent diameter: 13 arc seconds
Minimum apparent diameter from Earth: 4.5 arcseconds
Maximum optical magnitude: -1.9

Mercury Size

How big is Mercury? surface area, volume and equatorial diameter. Surprisingly, it is also one of the densest. She acquired her title of "smallest" after Pluto was demoted. This is why the old accounts refer to Mercury as the second smallest planet. The above are the three criteria we will use to show .

Some scientists believe that Mercury is actually contracting. The liquid core of the planet occupies 42% of the volume. The rotation of the planet allows to cool a small part of the core. This cooling and contraction is believed to be evidenced by cracks in the planet's surface.

Much like , and the continued presence of these craters indicates that the planet has not been geologically active for billions of years. This knowledge is based on partial mapping of the planet (55%). It is unlikely to change even after MESSENGER maps the entire surface [ed. note: as of April 1, 2012]. The planet was most likely heavily bombarded by asteroids and comets during the Late Heavy Bombardment about 3.8 billion years ago. Some regions would be filled with magmatic eruptions from within the planet. These cratered smooth plains are similar to those found on the Moon. As the planet cooled, individual cracks and ravines formed. These features can be seen on top of other features which are a clear indication that they are new. Volcanic eruptions ceased on Mercury about 700-800 million years ago, when the planet's mantle contracted enough to prevent lava flows.

The WAC image, showing a never-before-photographed region of Mercury's surface, was taken from an altitude of about 450 km above Mercury. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington.

Mercury diameter (and radius)

The diameter of Mercury is 4,879.4 km.

Need a way to compare it to something more similar? The diameter of Mercury is only 38% of the diameter of the Earth. In other words, you could fit almost 3 Mercurys side by side to match the Earth's diameter.

In fact, there are those that have a larger diameter than Mercury. The largest moon in solar system is Jupiter's moon Ganymede, with a diameter of 5.268 km, and the second largest moon is , with a diameter of 5.152 km.

Earth's moon is only 3,474 km in diameter, so Mercury isn't much larger.

If you want to calculate the radius of Mercury, you need to divide the diameter in half. Since the diameter is 4,879.4 km, the radius of Mercury is 2,439.7 km.

Diameter of Mercury in kilometers: 4,879.4 km
Diameter of Mercury in miles: 3,031.9 miles
Radius of Mercury in kilometers: 2,439.7 km
Radius of Mercury in miles: 1,516.0 miles

Circumference of Mercury

The circumference of Mercury is 15.329 km. In other words, if Mercury's equator were perfectly flat and you could drive a car over it, your odometer would add 15.329 km to travel.

Most planets are spheroids compressed at the poles, so their equatorial circumference is greater than from pole to pole. The faster they rotate, the more flattened the planet is, so the distance from the center of the planet to its poles is shorter than the distance from the center to the equator. But Mercury rotates so slowly that its circumference doesn't depend on where you measure it.

You can calculate the circumference of Mercury yourself using classic math formulas to get the circumference of a circle.

Circumference = 2 x Pi x radius

We know that the radius of Mercury is 2,439.7 km. So if you plug these numbers into: 2 x 3.1415926 x 2439.7 you get 15.329 km.

Circumference of Mercury in kilometers: 15.329 km
Circumference of Mercury in miles: 9.525 km

Crescent of Mercury.

Volume of Mercury

The volume of Mercury is 6.083 x 10 10 km 3 . It seems like a huge number, but Mercury is the smallest planet in the solar system by volume (downgraded to Pluto). It is even smaller than some of the moons in our solar system. The volume of Mercury is only 5.4% of the volume of the Earth, and the Sun is 240.5 million times larger than Mercury in volume.

More than 40% of the volume of mercury is occupied by its core, to be exact 42%. The core has a diameter of about 3,600 km. This makes Mercury the second densest planet among our eight. The core is molten and mostly iron. The molten core can produce a magnetic field that helps reflect the solar wind. The planet's magnetic field and negligible gravity allows it to maintain a negligible atmosphere.

It is believed that Mercury was at one time the larger planet; therefore, had a larger volume. There is one theory to explain its current size that many scientists have accepted on several levels. The theory explains the density of mercury and the high percentage of matter in the core. The theory states that Mercury originally had a ratio of metals to silicates similar to ordinary meteorites, as is characteristic of rocky matter in our solar system. At the time, the planet is believed to have had a mass of about 2.25 times its current mass, but early in the Solar System's history it was hit by a planetesimal that was 1/6th of its mass and several hundred kilometers in diameter. The impact scraped away much of the original crust and mantle, leaving the core as most of the planet and greatly reducing the planet's volume.

Volume of Mercury in cubic kilometers: 6.083 x 10 10 km 3 .

Mass of Mercury
The mass of Mercury is only 5.5% of the earth's mass; actual value 3.30 x 10 23 kg. Since Mercury is the smallest planet in the solar system, you would expect it to be a relatively small mass. On the other hand, Mercury is the second densest planet in our solar system (after Earth). Given its size, the density comes mostly from the core, estimated at nearly half the planet's volume.

The mass of the planet is made up of substances that are 70% metallic and 30% silicate. There are several theories to explain why the planet is so dense and rich in metallic substances. Most of the widely supported theories support that a high core percentage is the result of an impact. In this theory, the planet originally had a ratio of metals to silicates similar to the chondrite meteorites common in our Solar System and 2.25 times its current mass. Early in the history of our universe, Mercury hit a planetesimal-sized impact object that was 1/6 of Mercury's hypothetical mass and hundreds of kilometers in diameter. An impact of this magnitude would have scraped away much of the crust and mantle, leaving a huge core. Scientists believe that a similar incident created our moon. An additional theory says that the planet formed before the Sun's energy stabilized. The planet had a much larger mass in this theory, but the temperatures created by the protosun would have been very high, around 10,000 Kelvin, and most of the rock on the surface would have been vaporized. The rock vapor could then be blown away by the solar wind.

Mass of Mercury in kilograms: 0.3302 x 1024 kg
Mass of Mercury in pounds: 7.2796639 x 1023 pounds
Mass of Mercury in metric tons: 3.30200 x 1020 tons
Mass of Mercury in tons: 3.63983195 x 10 20

An artist's conception of a MESSENGER in orbit around Mercury. Credit: NASA

Mercury's gravity

Mercury's gravity is 38% of Earth's gravity. A person weighing 980 Newtons (about 220 pounds) on Earth would only weigh 372 Newtons (83.6 pounds) landing on the surface of the planet. Mercury is only slightly larger than our Moon, so you can expect gravity to be similar to the moon's 16% of Earth's. The Big Difference in Mercury's Higher Density - It is the second densest planet in the Solar System. In fact, if Mercury were the same size as the Earth, it would be even denser than our own planet.

It is important to clarify the difference between mass and weight. Mass is a measure of how much substance something contains. Therefore, if you have 100 kg of mass on Earth, you have the same amount on Mars, or in intergalactic space. Weight, however, is the gravitational force you feel. Although bathroom scales measure in pounds or kilograms, they should actually measure in newtons, which are a measure of weight.

Take your current weight in either pounds or kilograms and then multiply by 0.38 on the calculator. For example, if you weigh 150 pounds, you would weigh 57 pounds on Mercury. If you weigh 68 kg on a floor scale, your weight on Mercury would be 25.8 kg.

You can also flip this number to figure out how much stronger you would be. For example, how high you could jump, or how much weight you could lift. The current high jump world record is 2.43 meters. Divide 2.43 by 0.38 and you would have a world high jump record if it were reached on Mercury. In this case, it would be 6.4 meters.

In order to avoid Mercury's gravity, you need to move at a speed of 4.3 km/s, or about 15,480 km/h. Compare this to Earth, where the escape velocity (ESV) of our planet is 11.2 km/s. If you compare the ratio between two planets, you get 38%.

Gravity on the surface of Mercury: 3.7 m/s 2
Escape velocity (second space velocity) of Mercury: 4.3 km/s

Density of Mercury

The density of Mercury is the second highest in the Solar System. Earth is the only denser planet. It is equal to 5.427 g/cm 3 compared to the earth's density of 5.515 g/cm 3 . If gravitational contraction were removed from the equation, Mercury would be denser. The high density of the planet is a sign of a large percentage of the core. The core makes up 42% of the total volume of Mercury.

Mercury is a terrestrial planet like Earth, only one of four in our solar system. Mercury has about 70% metallic substances and 30% silicates. Add in the density of Mercury and scientists can deduce the details of its internal structure. While the Earth's high density is largely responsible for the gravitational contraction at the core, Mercury is much smaller and not as much compressed internally. These facts have led NASA scientists and others to speculate that its core must be large and contain crushing amounts of iron. Planetary geologists estimate that the planet's molten core comprises about 42% of its volume. On Earth, the core occupies 17%.

Internal structure of Mercury.

This leaves the silicate mantle only 500-700 kkm thick. Data from Mariner 10 led scientists to believe that the crust is even thinner, on the order of 100-300 km. The mantle surrounds the core, which has more iron than any other planet in the solar system. So what caused this disproportionate amount of core matter? Most scientists accept the theory that Mercury had a ratio of metals to silicates similar to common meteorites - chondrites - several billion years ago. They also believe that it had a mass of 2.25 times its current mass; however, Mercury may have hit a planetesimal 1/6 the mass of Mercury and hundreds of kilometers in diameter. The impact would have scraped away much of the original crust and mantle, leaving a larger percentage of the planet at the core.

While scientists have a few facts about Mercury's density, there are more to be discovered. Mariner 10 sent back a lot of information, but was able to study only 44% of the planet's surface. fills in the gaps on the map as you read this article, and the BepiColumbo mission will go further in expanding our knowledge of this planet. Soon, more theories will emerge to explain the high density of the planet.

Density of Mercury in grams per cubic centimeter: 5.427 g/cm 3 .

Axis of Mercury

Like all planets in the Solar System, Mercury's axis is tilted from . In this case, the axial tilt is 2.11 degrees.

What exactly is the axial tilt of the planet? First imagine that the Sun is a ball in the middle of a flat disc, like a vinyl disc or CD. The planets are in orbit around the Sun inside this disk (larger or smaller). This disk is known as the plane of the ecliptic. Each planet also rotates on its own axis when it is in orbit around the sun. If the planet rotated perfectly straight up and down, then this line through the north and south poles of the planet would be perfectly parallel with the poles of the Sun, the planet would have an axial tilt of 0 degrees. Of course, none of the planets has such an inclination.

So if you were to draw a line between the north and south poles of Mercury and compare it to an imaginary line, Mercury would have no axial tilt at all, that angle would be 2.11 degrees. You might be surprised to know that Mercury's tilt is the smallest of all the planets in the solar system. For example, the tilt of the Earth is 23.4 degrees. And Uranus is generally turned upside down on its axis and rotates with an axial inclination of 97.8 degrees.

Here on Earth, the axial tilt of our planet causes the seasons. When it's summer in the northern hemisphere North Pole deflected outward. You get more sunlight in the summer, so it's warmer, and less in the winter.

Mercury does not experience any seasons. Due to the fact that it has almost no axial tilt. Of course, it doesn't have much of an atmosphere to keep the sun warm. Any side facing the Sun heats up to 700 Kelvin, while the side away from the Sun has temperatures below 100 Kelvin.

Axial tilt of Mercury: 2.11°.

Photo taken from the MESSENGER spacecraft.

The planet Mercury is the most close planet to the sun. It is located at a distance of only 58 million km from our star (for comparison, from the Earth to the Sun 150 million km). Like all planets, it is named after a Roman god, in this case, the Roman god of commerce - just like the ancient Greek god Hermes.

Its diameter is only 4879 km, which makes it the smallest planet in the solar system. It is even smaller than the moons Ganymede and Titan. But it has a metallic core, which is almost half the volume of the planet. This gives it a lot of mass and strong gravity, more than one might expect. On Mercury, your weight would be 38% of your weight on Earth.

Orbit

Mercury revolves around the Sun in a highly elongated elliptical orbit.

At its closest point, it approaches the Sun at 46 million km, and then moves away to 70 million km. It takes the planet only 88 days to orbit the sun.

At first glance, Mercury is very similar to our moon. It has a cratered surface as well as ancient lava flows. The largest crater is the Kaloris basin, almost 1300 km across. Like our Moon, it has no discernible atmosphere. But below the surface is very different from the moon. It has a huge iron core surrounded by a thick layer of mantle rocks and thin crust. gravity on the planet is 1/3 of Earth's.

It slowly rotates around its axis, making one revolution in 59 days.

Atmosphere

It is very sparse and consists of trapped particles of the solar wind. Without an atmosphere, it cannot retain heat from the sun. The side that faces the Sun heats up to 450°C while the shady side cools down to -170°C.

Study

BepiColumbo, which was launched to explore the planet

The first spacecraft to reach Mercury was Mariner 10, which flew past the planet in 1974. He was able to photograph about half of the planet's surface over several flybys. Then in 2004 NASA launched the MESSENGER spacecraft mission. At the moment, the spacecraft has entered orbit and is studying it in great detail.

If you want to see it without a telescope, it's difficult because the planet is in the bright rays of the Sun most of the time.

During the visibility period, you can see it in the west just after sunset, or in the east before sunrise. In a telescope, a planet has phases, like that of the moon, depending on the position in its orbit.

Mercury - the smallest planet in, is at the closest distance from the Sun, belongs to the terrestrial planets. The mass of Mercury is about 20 times less than that of the earth, and the planet has no natural satellites. According to scientists, the planet has a frozen iron core, which occupies about half of the planet's volume, followed by a mantle, and a silicate shell on the surface.

The surface of Mercury is very reminiscent of the moon, and is densely covered with craters, most of which are of impact origin - from a collision with fragments that have remained since the formation of the solar system about 4 billion years ago. The surface of the planet is covered with long, deep cracks, which may have formed as a result of the gradual cooling and compression of the planet's core.

The similarity of Mercury and the Moon lies not only in the landscape, but also in a number of other features, in particular, the diameter of both celestial bodies- 3476 km for the Moon, 4878 for Mercury. A day on Mercury is about 58 Earth days, or exactly 2/3 of a Mercury year. Another curious fact of the “lunar” similarity is connected with this - from the Earth, Mercury, like the Moon, always sees only the “front side”.

The same effect would have been if the Mercury day were exactly equal to the Mercury year, so before the beginning of the space age and observations using radar, it was believed that the period of rotation of the planet around its axis is 58 days.

Mercury moves very slowly around its axis, but it moves very quickly in orbit. On Mercury, a solar day is equal to 176 Earth days, that is, during this time, thanks to the addition of orbital and axial movements, two “Mercurian” years have time to pass on the planet!

Atmosphere and temperature on Mercury

Thanks to spacecraft, it was possible to find out that Mercury has an extremely rarefied helium atmosphere, which contains an insignificant state of neon, argon and hydrogen.

As for the actual properties of Mercury, they are in many ways similar to those of the moon - on the night side the temperature drops to -180 degrees Celsius, which is enough to freeze carbon dioxide and liquefy oxygen, on the daytime it rises to 430, which is enough to melt lead and zinc . However, due to the extremely weak thermal conductivity of the loose surface layer, already at a depth of a meter, the temperature stabilizes at plus 75.

This is due to the absence of a noticeable atmosphere on the planet. However, there is still some semblance of an atmosphere - from atoms emitted as part of the solar wind, mostly metallic.

Study and observation of Mercury

It is possible to observe Mercury, even without the help of a telescope, after sunset and before sunrise, however, certain difficulties arise due to the location of the planet, even during these periods it is not always noticeable.

In the projection onto the celestial sphere, the planet is visible as a star-shaped object that does not depart from the Sun further than 28 degrees of arc, with a strongly variable brightness - from minus 1.9 to plus 5.5 magnitude, that is, approximately 912 times. It is possible to notice such an object at dusk only in ideal atmospheric conditions and if you know where to look. And the displacement of the "star" per day exceeds four degrees of the arc - it was for this "speed" that the planet at one time received its name in honor of the Roman god of trade with winged sandals.

Near perihelion, Mercury comes so close to the Sun, and its orbital speed increases so much that for an observer on Mercury, the Sun moves backwards. Mercury is so close to the Sun that it is very difficult to observe it.

In mid-latitudes (including Russia), the planet is noticeable only in the summer months and after sunset.

You can observe Mercury in the sky, but you need to know exactly where to look - the planet is visible very low above the horizon (lower left corner)

The temperature on the surface of Mercury varies significantly: from -180 C on the dark side to +430 C on the sunny side. At the same time, since the axis of the planet almost does not deviate from 0 degrees, even on the planet closest to the Sun (at its poles), there are craters, the bottom of which the sun's rays never reached.

2. Mercury makes one revolution around the Sun in 88 Earth days, and around its axis one revolution in 58.65 days, which is 2/3 of one year on Mercury. This paradox is caused by the fact that Mercury is affected by the tidal influence of the Sun.

3. Mercury's magnetic field strength is 300 times less than the magnetic field strength of the planet Earth, the magnetic axis of Mercury is inclined to the axis of rotation by 12 degrees.

4. Mercury is the smallest of all the planets of the terrestrial group, it is so small that it is inferior in size to the largest satellites of Saturn and Jupiter - Titan and Ganymede.

5. Despite the fact that Venus and Mars are closest to the Earth in terms of their orbits, Mercury is closer to the Earth for a longer period of time than any other planet.

6. The surface of Mercury resembles the surface of the Moon - it, like the Moon, is dotted with a large number of craters. The biggest and most important difference between these two bodies is the presence on Mercury a large number jagged slopes - the so-called scarps, which stretch for several hundred kilometers. They were formed by compression, which accompanied the cooling of the planet's core.

7. Almost the most noticeable detail on the surface of the planet is the Plain of Heat. This is a crater that got its name due to its location near one of the "hot longitudes". 1300 km is the diameter of this crater. A body that hit the surface of Mercury in ancient times must have had a diameter of at least 100 km.

8. Around the sun, the planet Mercury rotates at an average speed of 47.87 km / s, which makes it the most fast planet solar system.

9. Mercury is the only planet in the solar system that has Joshua effect. This effect looks like this: the Sun, if we were to observe it from the surface of Mercury, at a certain moment would have to stop in the sky, and then continue moving, but not from east to west, but vice versa - from west to east. This is possible as a result of the fact that for about 8 days the rotational speed of Mercury is less than the orbital speed of the planet.

10. Not so long ago, thanks to mathematical modeling, scientists came up with the assumption that Mercury is not an independent planet, but a long-lost satellite of Venus. However, while there is no material evidence, this is nothing more than a theory.

Mercury is the first planet in the solar system. Not so long ago, it occupied almost the last place among all 9 planets in terms of its size. But, as we know, under the Moon nothing lasts forever. In 2006, Pluto lost planetary status due to its oversized size. He began to be called dwarf planet. Thus, Mercury is now at the end of a series of cosmic bodies that cut innumerable circles around the Sun. But it's about size. In relation to the Sun, the planet is closest - 57.91 million km. This is the average value. Mercury rotates in an overly elongated orbit, the length of which is 360 million km. That is why it is sometimes further from the Sun, then, on the contrary, closer to it. At perihelion (the point of the orbit closest to the Sun), the planet approaches the flaming star at 45.9 million km. And at aphelion (the farthest point of the orbit), the distance to the Sun increases and equals 69.82 million km.

Regarding the Earth, here the scale is slightly different. Mercury from time to time approaches us up to 82 million km or diverges up to a distance of 217 million km. The smallest figure does not mean at all that the planet can be carefully and for a long time examined in a telescope. Mercury deviates from the Sun by an angular distance of 28 degrees. From here it emerges that this planet can be observed from the Earth just before dawn or after sunset. You can see it almost at the horizon line. Also, you can not see the whole body as a whole, but only half of it. Mercury is rushing in orbit at a speed of 48 km per second. The planet makes a complete revolution around the Sun in 88 Earth days. The value that shows how different an orbit is from a circle is 0.205. The run-up between the plane of the orbit and the plane of the equator is 3 degrees. This suggests that the planet is characterized by minor seasonal changes. Mercury is a terrestrial planet. This also includes Mars, Earth and Venus. All of them have a very high density. The diameter of the planet is 4880 km. As it is not a shame to realize, but here even some satellites of the planets bypassed it. Diameter of the major satellite, Ganymede, which orbits Jupiter, is 5262 km. Titan, a satellite of Saturn, has no less solid appearance. Its diameter is 5150 km. The diameter of Callisto (satellite of Jupiter) is 4820 km. The Moon is the most popular satellite in the solar system. Its diameter is 3474 km.

Earth and Mercury

It turns out that Mercury is not so unpresentable and nondescript. Everything is known in comparison. A small planet loses well in size to the Earth. Compared to our planet, this small cosmic body looks like a fragile creature. Its mass is 18 times less than the earth's, and its volume is 17.8 times. The area of Mercury lags behind the area of the Earth by 6.8 times.

Features of Mercury's orbit

As mentioned above, the planet makes a complete revolution around the Sun in 88 days. It rotates around its axis in 59 Earth days. The average speed is 48 km per second. Mercury moves slower in some parts of its orbit, faster in others. Its maximum speed at perihelion is 59 km per second. The planet tries to skip the closest area to the Sun as soon as possible. At aphelion, Mercury's speed is 39 km per second. The interaction of speed around the axis and speed along the orbit gives a striking effect. For 59 days, any part of the planet is in one position to the starry sky. This section returns to the Sun after 2 Mercurial years or 176 days. From this it turns out that the solar day on the planet is equal to 176 days. At perihelion there is interesting fact. Here, the orbital rotation speed becomes greater than the movement around the axis. This is how the effect of Joshua (the leader of the Jews who stopped the Sun) arises at longitudes that are turned towards the luminary.

Sunrise on the planet

The sun stops and then starts moving in reverse side. The luminary tends to the East, completely ignoring the western direction destined for it. This continues for 7 days, until Mercury passes the closest part of its orbit to the Sun. Then its orbital speed begins to decrease, and the movement of the Sun slows down. In the place where the speeds coincide, the luminary stops. A little time passes, and it begins to move in the opposite direction - from east to west. Regarding longitudes, the picture is even more surprising. If people lived here, they would watch two sunsets and two sunrises. Initially, the Sun would have risen, as expected, in the east. In a moment it would stop. After the beginning of the movement back and would disappear over the horizon. After 7 days, it would again shine in the east and make its way to highest point in the sky. Such striking features of the planet's orbit became known in the 60s. Previously, scientists believed that it is always turned to the Sun on one side, and moves around the axis at the same speed as around the yellow star.

The structure of Mercury

Until the first half of the 70s, little was known about its structure. In 1974, in March, the interplanetary station Mariner-10 flew 703 km from the planet. She repeated her maneuver in September of the same year. Now its distance to Mercury was equal to 48 thousand km. And in 1975, the station made another orbit at a distance of 327 km. It is noteworthy that the magnetic field was recorded by the equipment. It did not represent a powerful formation, but compared to Venus, it looked quite significant. Mercury's magnetic field is 100 times smaller than Earth's. Its magnetic axis is 2 degrees out of alignment with the axis of rotation. The presence of such a formation confirms that this object has a core, where this very field is created. Today there is such a scheme for the structure of the planet - Mercury has an iron-nickel hot core and a silicate shell that surrounds it. The core temperature is 730 degrees. The nucleus is large. It contains 70% of the mass of the entire planet. The core diameter is 3600 km. The thickness of the silicate layer is within 650 km.

planet surface

The planet is littered with craters. In some places they are located very densely, in others there are very few of them. The largest crater is Beethoven, its diameter is 625 km. Scientists suggest that the flat terrain is younger than that dotted with many sinkholes. It was formed due to eruptions of lava, which covered all the craters and made the surface even. Here is the largest formation, which is called the Heat Plain. This is an ancient crater with a diameter of 1300 km. It is surrounded by a mountainous ring. It is believed that lava eruptions flooded this place and made it almost invisible. Opposite this plain there are many hills that can reach a height of 2 km. The lowlands are narrow. Apparently, a large asteroid that fell on Mercury provoked a shift in its bowels. In one place a large dent was left, and on the other side the crust rose and thus formed a displacement of rocks and faults. Something similar can be observed in other parts of the planet. These formations have a different geological history. Their shape is wedge-shaped. The width reaches tens of kilometers. It seems that this is a rock that was squeezed out under enormous pressure from the deep bowels.

There is a theory that these creations arose with a decrease in the temperature regimes of the planet. The core began to cool and shrink at the same time. Thus, upper layer also began to decrease. Bark shifts were provoked. This is how this peculiar landscape of the planet was formed. Now temperature conditions Mercury also have certain specifics. Given that the planet is close to the Sun, the conclusion follows: the surface that faces the yellow star has too high a temperature. Its maximum can be 430 degrees (at perihelion). In aphelion, respectively, cooler - 290 degrees. In other parts of the orbit, the temperature fluctuates between 320-340 degrees. It is easy to guess that at night the situation here is completely different. At this time, the temperature is kept at minus 180. It turns out that in one part of the planet there is a terrible heat, and in another at the same time terrible cold. An unexpected fact that the planet has reserves of water ice. It is found at the bottom of large craters at polar points. The sun's rays do not penetrate here. Mercury's atmosphere contains 3.5% water. It is delivered to the planet by comets. Some collide with Mercury as they approach the Sun and stay there forever. The ice melts into water and it evaporates into the atmosphere. At cold temperatures, it settles to the surface and turns back into ice. If it was at the bottom of the crater or at the pole, it freezes and does not return to the gaseous state. Since temperature differences are observed here, the conclusion follows: the cosmic body has no atmosphere. More precisely, there is a gas cushion available, but it is too rarefied. Main chemical element This planet's atmosphere is helium. It is brought here by the solar wind, a stream of plasma that flows out of the solar corona. Its main constituents are hydrogen and helium. The first is present in the atmosphere, but in a smaller ratio.

Research

Although Mercury is not at a great distance from the Earth, its study is quite difficult. This is due to the peculiarities of the orbit. This planet is very difficult to see in the sky. Only by observing it up close, you can get a complete picture of the planet. In 1974, such an opportunity arose. As already mentioned, this year there was an interplanetary station "Mariner-10" near the planet. She took pictures that mapped nearly half of Mercury's surface. In 2008, the Messenger station honored the planet with attention. Of course, they will continue to study the planet. What surprises it will present, we will see. After all, space is so unpredictable, and its inhabitants are mysterious and secretive.