Let's return to the Earth-Moon pair and illustrate some of their interactions with the following figure. For clarity, all scales on it are violated, and the considered distances, forces, speeds, details and processes are repeatedly exaggerated. However, the qualitative side of the phenomena, the essence of the matter, does not suffer from this.
The hypothetical observer is on high altitude, approximately above north pole Earth* (blue ball on the left). Point O1 is both the center of the Earth and the projection of the pole (more precisely, both poles) onto the drawing plane. The yellow ball on the right is the Moon.
*Note(for precision lovers). Due to the tilt earth's axis, it is better for the observer to be not above the pole itself, but at any distant point of the perpendicular established from the center of the Earth in relation to the plane of the Moon’s orbit (which itself does not coincide slightly, by about 5 degrees, with the plane of the Earth’s orbit - the ecliptic). And even more precisely, drawn through the GCM point (see below), and not through the center of the Earth itself. However, none of these three clarifications doesn't change anything in the bycatch mechanism under consideration (but only complicates the understanding of the issue). It does not depend in any way on the location (or presence) of the observer.
Both of these cosmic bodies together rotate (with a periodicity of about 29 days) around their common center of mass OCM, and he himself moves along the so-called. "Earth's orbit" around the Sun. (Due to its large radius, it is conventionally shown as a straight line segment). It is somehow not customary to notice the rotation of the Earth itself around the GCM with a lunar (almost monthly) cycle. True, this has almost nothing to do with the problem of tides. (But fairness is important).
Under the influence of the gravitational force of the Moon, the globe (and molten subsoil, and Earth's crust with the oceans, and the atmosphere) turns into ellipsoid, elongated in the direction of the Moon (indicated in red, on the left). Closest point to the Moon earth's surface 1 moves to position 2.
Note that this elongation is on average less than one meter. Large difference in water level at sea tides and low tides (in some places on the planet - more than 10 meters) is explained by significant ocean masses of water collected from distances of thousands of kilometers in relatively small shallow waters.
The right (according to the drawing) elevation of the Earth's surface level (point 2) is caused directly by the gravitational force of the Moon. The opposite, left elevation is caused, perhaps, by the specifics of the forces surface tension spherical melt of the planet, which is subject to a lateral force. (The author has no firm confidence in the correctness of this explanation.) In the case of a thick layer of crust (or a completely cooled core), the picture would be similar due to the elastic forces of the solid rocks of the planet.
Other interpreters explain the left elevation by the difference in gravity in different places deformed globe. In the direction perpendicular to the Earth-Moon line, in the low tide zone, the diameter of the Earth is smaller (due to the constancy of the total volume of the planet), which means that gravity is there greatest. And since on average it is unchanged on Earth, it means that on the left there are several smaller. That is why a left elevation is formed there (Perhaps this explanation is correct).
One way or another, in real life ebbs and flows on Earth alternate every 6 hours, so the picture of an ellipsoid elongated in both directions is beyond any doubt.
Due to the relatively rapid rotation of the Earth around its axis ( linear speed surface movement near the equator is approximately 460 m/s), the top of the tidal elevation accumulated at point 2 (no matter whether it is water or land!) is constantly carried away at this speed to the east, to point 3. At point 2, the surface is again slightly raised by the gravitational force of the Moon, but this elevation is again carried away to point 3. Thus, the real position of the top of the tidal rise, point 3, is always shifted in the direction of the Earth’s rotation by an angle of approximately 2 degrees (in the figure indicated by a red arc going from point 2 to point 3 ).
A similar tidal elevation due to the Earth's gravitational force is also present on the solid Moon. According to calculated data, point 5 is elevated above the level of the standard sphere of the Moon (point 4) by 13 meters. Since the Moon is always turned to the earth with one side, the position of point 5 is unchanged both for an terrestrial observer and for an observer located on the Moon itself. (That is, it is a fixed point on the map of the visible part of the Moon).
The gravitational force of the Moon affects not only the entire Earth, but also, in particular, both tidal elevations on Earth. Since the left one is located significantly, almost 13,000 km further, the main impact occurs precisely on the right elevation, the center of which is located at point 3. (This impact is predominant and decisive, so we will only consider it further). Conventionally, it is indicated by force F1. Since its direction does not coincide with the direction to the center of the Earth, it acts on point 3 in such a way as to return it to point 2 (or at least closer to it).
In reality, this work (literally!) is done by force, equal F1, but directed oppositely to it and applied to point 3. This force has a vertical (in the drawing!) component (Ft), directed from t.3 to t.2.
And this component is concrete and real slows down rotation Earth ! Due to this, the length of the earth's day increases annually by 2.10^(-5) seconds. It seems like quite a bit. But what will happen, for example, in a million years? The day will increase by 20 seconds.
And in a few billion years?
Double planet- this is the Earth with the Moon. They have the right to this name because our satellite stands out sharply among the satellites of other planets due to its significant size and mass in relation to its central planet. There are satellites in the solar system absolutely larger and heavier, but in comparison with their central planet they are much smaller than our Moon in relation to the Earth. In fact, the diameter of our Moon is more than a quarter of the Earth’s, and the diameter relative to the largest satellite of other planets is only a 10th of the diameter of its planet (Triton is a satellite of Neptune). Further, the Moon's mass is 1/81 that of the Earth; Meanwhile, the heaviest of the satellites that exists in the solar system, the III satellite of Jupiter, is less than 10,000th of the mass of its central planet.
What proportion of the mass of the central planet is the mass of large satellites is shown in the table below. You can see from this comparison that our Moon, by its mass, makes up the largest fraction of its central planet.
The third thing that gives the Earth-Moon system the right to claim the name “double planet” is the close proximity of both celestial bodies. Many satellites of other planets circle at much long distances: some of Jupiter's moons (for example, the ninth, Fig. 36) circle 65 times further.
Rice. 36.
In connection with this is the curious fact that the path described by the Moon around the Sun differs very little from the path of the Earth. This will seem incredible if you remember that the Moon moves around the Earth at a distance of almost 400,000 km. Let us not forget, however, that while the Moon makes one revolution around the Earth, the Earth itself manages to move along with it approximately the 13th part of its annual path, i.e. 70,000,000 km. Imagine the circular path of the Moon - 2,500,000 km - stretched along a distance 30 times greater. What will remain of its circular shape? Nothing. That is why the path of the Moon near the Sun almost merges with the Earth’s orbit, deviating from it only by 13 barely noticeable protrusions. It can be proven with a simple calculation (which we will not burden the exposition here) that the path of the Moon is everywhere directed towards its Sun concavity. Roughly speaking, it looks like a convex thirteen-sided triangle with softly rounded corners.
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Her companion |
(in fractions of the planet's mass) |
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In Fig. 37 you see an accurate depiction of the paths of the Earth and Moon over the course of one month. The dotted line is the path of the Earth, the solid line is the path of the Moon. They are so close to each other that to depict them separately we had to take a very large drawing scale: the diameter of the earth’s orbit here is 1/2 m. If we took 10 cm for it, then the greatest distance in the drawing between both paths would be less than the thickness of the depicted their lines. Looking at this drawing, you are clearly convinced that the Earth and the Moon move around the Sun almost along the same path and that the name double planet was assigned to them by astronomers quite rightly.
Rice. 37.
So, to an observer placed on the Sun, the Moon's path would appear to be a slightly wavy line, almost coinciding with the Earth's orbit. This does not at all contradict the fact that in relation to the Earth the Moon moves along a small ellipse.
The reason, of course, is that, looking from the Earth, we do not notice the portable movement of the Moon along with the Earth. earth's orbit, because we ourselves participate in it.
- Carefully examining the drawing, you can see that the movement of the Moon is not depicted as strictly uniform. This is actually true. The Moon moves around the Earth in an ellipse, the focus of which is the Earth, and therefore, according to Kepler’s second law, it runs faster in areas close to the Earth than in areas farther away. Eccentricity lunar orbit Quite large: 0.055.
phases relative to the rays of the Sun. The impression is as if the rays of the Sun are bent before reaching the Moon.
The answer lies in the following. The ray going from the Sun to the Moon is actually perpendicular to the line connecting the ends of the month
Rice. 36. In what position relative to the Sun do we see the Moon in different phases.
tsa, and in space it is a straight line. But our eye draws not this straight line in the sky, but its projection onto the concave vault of the sky, that is, a curved line. This is why it seems to us that the Moon is “hung incorrectly” in the sky. The artist must study these features and be able to transfer them to the canvas.
Double planet
A double planet is the Earth and the Moon. They have the right to this name because our satellite stands out sharply among the satellites of other planets due to its significant size and mass in relation to its central planet. There are satellites in the solar system that are absolutely larger and heavier, but in comparison with their central planet they are much smaller than our Moon in relation to the Earth. In fact, the diameter of our Moon is more than a quarter of the Earth’s, and the diameter relative to the largest satellite of other planets is only a 10th of the diameter of its planet (Triton is a satellite of Neptune). Further, the mass of the Moon is 1/81 the mass of the Earth; Meanwhile, the heaviest satellite that exists in the solar system, the III satellite of Jupiter, is less than 10,000th of the mass of its central planet.
What proportion of the mass of the central planet is the mass of large satellites is shown by the plate on page 50.
You can see from this comparison that our Moon, in terms of its mass, makes up the largest share of its central planet.
The third thing that gives the Earth-Moon system the right to claim the name “double planet” is the close proximity of both celestial bodies. Many satellites of other planets circle at much greater distances: some satellites of Jupiter (for example, the ninth, Fig. 37 ) circle 65 times further.
In connection with this is the curious fact that the path described by the Moon around the Sun differs very little from the path of the Earth. This will seem incredible if you remember that the Moon moves around the Earth at a distance of almost 400,000 km. Let us not forget, however, that for now
The Moon makes one revolution around the Earth, the Earth itself manages to move along with it approximately the 13th part of its annual path, i.e.
Her companion | Weight (in fractions) |
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mass of the planet) |
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Rice. 37. The Earth-Moon system compared with the Jupiter system. (The dimensions of the celestial bodies themselves are not shown to scale.)
70,000,000 km. Imagine the circular path of the Moon - 2,500,000 km - stretched along a distance 30 times greater. What will remain of its circular shape? Nothing. That is why the path of the Moon near the Sun almost merges with the Earth’s orbit, deviating from it only by 13 barely noticeable protrusions. It can be proven with a simple calculation (which we will not burden the exposition here) that the path of the Moon is everywhere facing the Sun with its concavity. Roughly speaking, it looks like a thirteen-sided triangle with softly rounded corners.
In Fig. 38 you see an accurate depiction of the paths of the Earth and Moon over the course of one month. The dotted line is the path of the Earth, the solid line is the path of the Moon. They are so close to each other that to depict them separately we had to take a very large drawing scale: the diameter of the earth’s orbit here is ½ m. If we took 10 cm for it, then the greatest distance in the drawing between both paths would be less than the thickness of the lines depicting them . Looking at this drawing, you are clearly convinced that the Earth and the Moon move around the Sun almost along the same path and that the name “double planet” was assigned to them by astronomers quite rightly1).
So, for an observer placed on the Sun, the path of the Moon would appear to be a slightly wavy line, almost coinciding with the orbit of the Earth. This does not at all contradict the fact that in relation to the Earth the Moon moves along a small ellipse.
1) Carefully examining the drawing, you can notice that the movement of the Moon is not depicted as strictly uniform. This is actually true. The Moon moves around the Earth in an ellipse, the focus of which is the Earth, and therefore, according to Kepler’s second law, it runs faster in areas close to the Earth than in areas farther away. The eccentricity of the lunar orbit is quite large: 0.055.
The reason, of course, is that, looking from the Earth, we do not notice the portable movement of the Moon along with the Earth in the Earth’s orbit, since we ourselves participate in it.
Why doesn't the Moon fall on the Sun?
The question may seem naive. Why on earth would the Moon fall on the Sun? After all, the Earth attracts her more strongly distant sun and, naturally, makes it revolve around itself.
Readers who think this way will be surprised to learn that the opposite is true: the Moon is more strongly attracted by the Sun, not by the Earth!
The calculation shows that this is so. Let's compare the forces that attract the Moon: the force of the Sun and the force of the Earth. Both forces depend on two circumstances: on the magnitude of the attractive mass and on the distance of this mass from the Moon. The mass of the Sun is 330,000 times greater than the mass of the Earth; the Sun would attract the Moon the same number of times more strongly than the Earth if the distance to the Moon were the same in both cases. But the Sun is about 400 times farther from the Moon than the Earth. The force of attraction decreases in proportion to the square of the distance; therefore, the attraction of the Sun must be reduced by 4002, i.e. 160,000 times. This means that solar gravity is 330,000 times stronger than the earth’s, i.e.
Rice. 38. Monthly path of Lupa ( solid line) and the Earth (dotted line) around the Sun.
more than two times.
So, the Moon is attracted by the Sun twice as much as by the Earth. Why then, in fact, is the Moon not
collapsing into the sun? Why does the Earth still force the Moon to revolve around it, and does not the action of the Sun take over?
The Moon does not fall on the Sun for the same reason that the Earth does not fall on it; The Moon revolves around the Sun together with the Earth, and the attractive effect of the Sun is spent without a trace in constantly transferring both of these bodies from straight path into a curved orbit, i.e. turn rectilinear movement into a curvilinear one. Just take a look at Fig. 38 to verify what was said.
Some readers may still have some doubts. How does this come out anyway? The Earth pulls the Moon towards itself, the Sun pulls the Moon with greater force, and the Moon, instead of falling on the Sun, circles around the Earth? It would indeed be strange if the Sun attracted only the Moon. But it attracts the Moon together with the Earth, the entire “double planet”, and, so to speak, does not interfere with internal relations members of this pair with each other. Strictly speaking, it is attracted to the Sun common center gravity of the Earth - Moon system; This center (called the “barycenter”) revolves around the Sun under the influence of solar gravity. It is located at a distance of ⅔ of the Earth's radius from the center of the Earth towards the Moon. The Moon and the center of the Earth revolve around the barycenter, completing one rotation every month.
Visible and invisible sides of the Moon
Among the effects delivered by a stereoscope, nothing is as striking as the view of the Moon. Here you see with your own eyes that the Moon is really spherical, whereas in the real sky it seems flat, like
tea tray. | |
But how difficult is it to get something like this? | |
stereoscopic photograph of our | |
satellite, many don’t even suspect. | |
To make it you have to be good | |
familiar with the characteristics of capricious | |
movements of the night star. | |
The fact is that the Moon goes around the Earth | |
so that it is addressed to her all the time alone and | |
the same side. | |
As the Moon circles the Earth, it rotates | Rice. 39. How the Moon moves around |
at the same time and around its axis, and |
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both movements end at the same time | Earth in its orbit. (Details - |
same period of time. | sti in the text.) |
In Fig. 39 you see an ellipse that should clearly depict the orbit of the Moon. The drawing deliberately enhances the elongation of the lunar ellipse; in fact, the eccentricity of the lunar orbit is 0.055 or 1/18. It is impossible to accurately represent the lunar orbit in a small drawing so that the eye can distinguish it from a circle: with the semi-major axis measuring even a whole meter, the semi-minor axis would be shorter than it by only 1 mm; The earth would be only 5.5 cm away from the center. To make it easier to understand the further explanation, a more elongated ellipse is drawn in the figure.
So, imagine that the ellipse in Fig. 39 is the path of the Moon around the Earth. The earth is placed at point O - at one of the foci of the ellipse. Kepler's laws apply not only to the movements of planets around the Sun, but also to the movements of satellites around central planets, in particular to the
to the glory of the moon. According to Kepler's second law, in a quarter of a month the Moon travels such a path AE that the area OABCDE is equal to ¼ the area of the ellipse, i.e. the area MABCD (the equality of the areas OAE and MAD in our drawing is confirmed by the approximate equality of the areas MOQ and EQD). So, in a quarter of a month the Moon travels from A to E. The rotation of the Moon, like the rotation of planets in general, in contrast to their revolution around the Sun, occurs evenly: in ¼ month it rotates exactly 90°. Therefore, when the Moon is in E, the radius of the Moon, facing the Earth at point A, will describe an arc of 90°, and will be directed not to point M, but to some other point, to the left of M, not far from another focus P of the lunar orbit. Because the Moon slightly turns its face away from the earthly observer, he will be able to see from right side a narrow strip of its previously invisible half. At point F, the Moon shows an observer on earth a narrower strip of its usually invisible side, because the angle OFP is less than the angle OEP. At point G - at the “apogee” of the orbit - the Moon occupies the same position in relation to the Earth as at “perigee” A. With its further movement, the Moon turns away from the Earth already at the opposite side, showing our planet another strip of its invisible side: this strip first expands, then narrows, and at point A the Moon takes its previous position.
We are convinced that, due to the elliptical shape of the lunar path, our satellite does not face the Earth with exactly the same half. The Moon invariably faces the same side not to the Earth, but to another focus of its orbit. For us, it sways around the middle position like a scale; hence the astronomical name for this rocking: “libration” - from Latin word"libra" meaning "scales". The amount of libration at each point is measured by the corresponding angle; for example, at point E the libration is equal to the angle OEP. Largest value libration 7°53", i.e. almost 8°.
It is interesting to watch how the libration angle increases and decreases as the Moon moves along its orbit. Let us place the tip of a compass at D and describe an arc passing through the foci O and P. It will intersect the orbit at points B and F. Angles OBP and OFP as inscribed are equal to half the central angle ODP. From this we conclude that when the Moon moves from A to D, the libration grows quickly at first, at point B it reaches half the maximum, then continues to increase slowly; On the way from D to F, the libration decreases first slowly, then quickly. In the second half of the ellipse, libration changes its value at the same rate, but at reverse side. (The amount of libration at each point in the orbit is approximately proportional to the distance of the Moon from the major axis of the ellipse.)
That wobble of the Moon, which we have just examined, is called libration in longitude. Our satellite is also subject to another libration - in latitude. The plane of the lunar orbit is inclined to the plane of the equator
Moon at 6½°. Therefore, we see the Moon from the Earth in some cases a little from the south, in others from the north, looking a little into the “invisible” half of the Moon through its poles. This libration in latitude reaches 6½°.
Let us now explain how the astronomer-photographer uses the described slight swaying of the Moon around its middle position in order to obtain stereoscopic photographs of it. The reader probably guesses that for this it is necessary to lie in wait for two such positions of the Moon, in which in one it would be rotated relative to the other at a sufficient angle1). At points A and B, B and C, C and D, etc. The Moon occupies such different positions relative to the Earth that stereoscopic photographs are possible. But here we are faced with a new difficulty: in these positions the difference in the age of the Moon, 2 days, is too great, so the strip lunar surface near the circle of lighting in one picture it is already coming out of the shadows. This is unacceptable for stereoscopic images (the strip will shine like silver). Arises difficult task: to lie in wait for identical phases of the Moon, which differ in the amount of libration (in longitude) so that the circle of illumination passes over the same parts of the lunar surface. But this is not enough: in both positions there must also be equal librations in latitude.
You now see how difficult it is to get good stereo photographs of the Moon, and you will not be surprised to learn that often one photograph of a stereoscopic pair is taken several years later than the other.
Our reader is unlikely to take lunar stereo photographs. The method of obtaining them is explained here, of course, not with practical purpose, but only for the sake of it to consider the features lunar movement, giving astronomers the opportunity to see a small strip of the usually inaccessible side of our satellite. Thanks to both lunar librations, we see, in general, not half of the entire lunar surface, but 59% of it. 41% remains completely inaccessible to our vision. No one knows how this part of the lunar surface is structured; one can only guess that it does not differ significantly from the visible one. Ingenious attempts were made, by continuing back parts of the lunar ridges and light stripes emerging from the invisible part of the Moon onto the visible one, to sketch out some fortune-telling details of the half inaccessible to us. It is not yet possible to verify such guesses. We say “yet” not without reason: methods have long been developed to fly around the Moon on a special aircraft, which can overcome the gravity of the earth and move in interplanetary space (see my book “Interplanetary Travel”). The implementation of this bold undertaking is now not so far away. So far, one thing is known: the often expressed idea about the existence of an atmosphere and water on this
1) To obtain stereoscopic images, a rotation of the Moon by 1° is sufficient. (For more on this, see my Fun Physics.)
Pluto was discovered in 1930. But 76 years later, the IAU deprived this object of the right to be called a planet and transferred it to the rank of dwarf planets. It is now believed that Pluto, like Eris, is only one of the largest neptunoids inhabiting the Kuiper Belt.
And in 1978, its main satellite, Charon, was identified. It was discovered while studying photographic plates depicting Pluto. On one of the plates, a hump appeared on the planet, which turned out to be a planet when examined.
Charon was originally named a satellite of Pluto, but now it is believed to be a double planet. Their common center of gravity is located outside main planet. This is a unique type of interaction. It is also unusual that they always face their counterparts with the same side.
But it's not actually confirmed yet...
Double planet- a term in astronomy that is used to indicate binary system, consisting of two astronomical objects, each of which meets the definition of a planet and is massive enough to exert gravitational effect, surpassing the gravitational effect of the star they orbit.
As of 2010, there are officially no systems in the Solar System classified as "double planets". One of the unofficial requirements is that both planets orbit a common center of mass, also called a barycenter, which must be above the surface of these planets.
Charon's diameter is 1205 km - slightly more than half that of Plutonian, and their masses have a ratio of 1:8. This is the mosta large satellite in the solar system in comparison with its planet. The distance between the objects is very small - 19.6 thousand km, and the satellite's orbital period is about a week.
From 1985 to 1990, a rather infrequent phenomenon was observed: eclipses. They alternated: at first one planet eclipsed the other, then vice versa. Such eclipses have a cycle of 124 years.
Analysis of the reflected light allows us to conclude that on the surface of Charon there is a layer water ice, in contrast to the methane-nitrogen at Pluto. According to the Gemini Observatory, ammonia hydrate and water crystals were found on Charon. This makes the existence of cryogeysers probable.
Unusual compared to other planets solar system, the parameters of the orbits of the planetary pair and their modest sizes give scientists hypotheses about their origin. It is believed that the planets formed in the Kuiper belt, and were torn out from there by the gravity of the giant planets.
Another hypothesis suggests the formation of the system after the collision of the already existing Pluto with the proto-Charon. The current satellite was formed from the ejected debris. And now they are together, Pluto and Charon - the distant outskirts of the solar system.
As mentioned above, the Pluto-Charon system meets the definition of a double planet. On currently these are the only bodies in the solar system that can claim such status.
According to draft Resolution 5 of the XXVI General Assembly of the IAU (2006), Charon was supposed to be given the status of a planet. The notes to the draft resolution indicated that in such a case Pluto-Charon would be considered double planet. The basis for this was the fact that each of the objects can be considered dwarf planet, and their common center of mass lies at open space. However, at the same assembly, the IAU introduced a definition of the concepts of “Planet” and “Dwarf Planet”. According to the introduced definitions, Pluto is classified as a dwarf planet, and Charon is its satellite, although this decision may be revised in the future
As spacecraft New Horizons continues its journey to the outer edge of the Solar System, its target - which lies in the Kuiper belt - becomes brighter and clearer. New images from the Long Range Reconnaissance Imager (LORRI) clearly show Pluto and its largest moon, Charon, locked in a tight orbital dance. The two objects are separated by a distance of just over 18,000 kilometers.
These images, which show Charon orbiting Pluto, are record-breaking in terms of the distance from which they were taken: 10 times less than the distance from Pluto to Earth.
We've already seen images of Pluto and Charon, but there's something else to see in this animation.
Over 5 days, LORRI took 12 images of the Pluto-Charon system, during which time Charon almost completely completed 1 revolution around Pluto. However, as Charon orbits, distinct fluctuations in Pluto's position can be observed. Charon's mass (about 12 percent of Pluto's mass) has a strong gravitational influence towards Pluto, very clearly pulling it “away from the center”. Therefore, both objects orbit an imaginary point above Pluto's surface. This point is called the center of gravity of the Pluto-Charon system.
Comparative sizes of trans-Neptunian objects compared to Earth.
This is a completely atypical situation for the planets of the Solar System - only dual systems asteroids may have barycenters (centers of gravity) outside the objects themselves. As a result, many scientists have come to the conclusion that Charon should be recognized as an independent planet, or the Pluto-Charon system should be designated as a double planet.
In 2012, a paper was published indicating that Pluto's four other moons do not actually orbit it. They follow an orbit around the center of gravity of the Pluto-Charon system, that is, they are satellites of Pluto and Charon, and not just Pluto!
However, international organization, which deals with the classification of celestial objects, should once again investigate this fact. Most likely, the International Astronomical Union will need to conduct re-study systems of Pluto and Charon, especially after next year Close-up images will be taken.
- Dwarf planet Pluto named after Roman god underworld. In Roman mythology, Pluto was the son of Saturn, who with his three brothers ruled the world: Jupiter controlled the sky, Neptune was the ruler of the seas, and Pluto ruled the underworld.
- Pluto's atmosphere is composed of nitrogen with some methane and carbon monoxide.
- Pluto is the only known dwarf planet to have an atmosphere. Pluto's atmosphere is unsuitable for human breathing and has a low altitude. When Pluto is at perihelion (closest to the sun), its atmosphere becomes gaseous. When Pluto is at apohelia (farthest from the sun), its atmosphere freezes and precipitates onto the planet's surface.
- It takes Pluto 248 to make a full revolution around the sun. earthly years. This is the most a long period revolutions around the center of our system of all the planets. The fastest of the planets in this regard is Mercury, which for full turn It takes 88 Earth days to circle the sun.
- To turn around once own axis Pluto takes 6 days, 9 hours and 17 minutes, making it the second slowest planet in the solar system to rotate. Only Venus rotates the slowest around its axis – in 243 Earth days. Jupiter, although the largest of the planets, rotates at a rate of one revolution in less than 10 Earth hours.
- Pluto rotates in the opposite direction to the Earth's rotation. This means that the sun there rises in the west and sets in the east. Only Venus, Uranus and Pluto rotate opposite to the earth's.
- Because Pluto's moon Charon is only slightly smaller than the planet itself, astronomers call them together a double planet.
- Sunlight takes five hours to reach Pluto, and to reach the Earth's surface sunbeam it only takes eight minutes.
- In astrology, Pluto is associated with both beginning (rebirth) and destruction (death).
- When Pluto was one of the planets of the solar system (now it is classified as a minor planet), it was considered the coldest of them. Its temperature ranges from -240° to -218° C. average temperature here -229° C. The most low temperature, registered on Earth, was recorded in Antarctica and was equal to -89.2° C, and our planet became hottest (up to 70.7°) in the Iranian desert of Lut.
- A person weighing 45 kg on Earth will weigh about 2 kg 750 g on Pluto.
- Pluto is so dark that a person would be able to admire the stars from its surface all day.
- Trying to see Pluto from Earth is like trying to see a walnut from a distance of 50 kilometers.
- Since the satellite Charon and Pluto itself rotate mutually around each other, from the surface of Pluto Charon appears frozen motionless in the sky. In addition, the same sides of Pluto and Charon are constantly directed towards each other.
- Pluto has four moons: Charon (named after the ferryman of hell), Nyx (after the Greek goddess of night and darkness), Hydra (named after the nine-headed snake that guards hell) and the as-yet unnamed moon S/2011 P 1, which was discovered quite recently (in 2011).
- No artificial flying object launched from Earth has ever visited Pluto. Nevertheless, interplanetary station New Horizons, launched in 2006, is scheduled to fly by Pluto in 2015.
- For 76 years, Pluto was considered a planet. However, when astronomers discovered that it was one of many large objects within the Kuyper belt, Pluto has been called a "dwarf planet" since 2006.
- Pluto is the second largest dwarf planet in the solar system. Only Eris is larger than it, which is 27% larger than Pluto.
- Pluto is smaller than Mercury and seven other moons different planets, including Ganymede, Titan, Callisto, Io, Triton and our Moon.
- When Pluto was discovered in 1930, many people proposed various names for him. The options were: Chronus, Persephone, Erebus, Atlas and Prometheus. Eleven-year-old Venetia Bernie suggested the name Pluto. She thought it would be good name, since the planet was so dark and so far away, as was the god of the underworld. On May 1, 1930, the name of the planet was officially assigned, and the girl received a reward of five pounds sterling.
- Many scientists believe that if Pluto were closer to the sun, it would be classified as a planet.
- Now official name Pluto is "asteroid number 134340". It was so named after being excluded from the planets of the solar system and being relegated to the rank of “dwarf planets”. ( Dwarf planets in astronomical catalogs they are designated as asteroids).
- While Pluto is "demoted" in rank to dwarf planet, many scientists are trying to classify it and several of its other brethren as planets again, since they have their own atmosphere, seasons, polar caps and their own satellites.
- Sunlight on Pluto is 2,000 times dimmer than on Earth, and from its surface the sun will only appear as a small dot in the sky.
- The official symbol of Pluto is the intertwined letters "P" and "L", which not only symbolize the name, but are also the initials of Percival Lowell, an American astronomer who initiated the search for a planet that was supposed to be located further than Neptune, which led to the discovery of Neptune. One of the observatories in American state Arizona is named after Lowell.
- On Pluto, the sun rises and sets about once a week.
Double planet Earth - Moon
The luminary of the night, the affectionate goddess Selene, as the ancient Greeks called her, the Moon invariably accompanies the Earth in its run around the Sun.
The Moon is the celestial body closest to us. The distance to it is only 384 thousand kilometers, according to on a cosmic scale- just a stone's throw away!
Compared to the Earth, the Moon is small. Its diameter is 3,476 kilometers, slightly more than a quarter of the Earth's, and its surface is equal to the area of Africa and Australia combined. The mass of the Moon is 81.3 times less than the mass of the Earth. And yet the Earth, in comparison with its size, has the most large satellite in the family of planets in the solar system.
Triton, Neptune's moon, is 770 times lighter than its planet; Titan, the most large satellite Saturn, 4030 times lighter than Saturn; largest moon Jupiter, Ganymede, is 12,200 times lighter than the planet. There is nothing to say about other satellites: their masses are tens and hundreds of thousands of times less than the masses of the planets around which they orbit. And that is why many astronomers call the Earth-Moon system a double planet.
In fact, the first people to view the Earth from Venus would see double star. One of them would appear very bright, and the other, located nearby, although much fainter, would be clearly visible.
The Earth, accompanied by the Moon, moves around the Sun.
How did the double planet Earth - Moon come into being? There are two assumptions on this score, or, to put it scientifically, two hypotheses.
The first one is this. Several billion years ago, both the Earth and the Moon, independently of one another, were formed from clumps of cosmic matter in various areas world space. And then the Moon, in its celestial wanderings, inadvertently came too close to the Earth, and our planet, using its greater mass, captured the Moon according to the laws of gravity and made her a companion.
According to the second hypothesis, both the Earth and the Moon were formed from one clump of matter. And at the beginning of their existence these two celestial bodies were much closer friend to friend. But gradually the Moon moved away from the Earth and took its present position. The younger sister continues to move away from the older one, but many millions of years will pass before this becomes noticeable.
It is difficult to say which of the two assumptions is more correct. Scientists will still have to work a lot to finally resolve the question of the origin of the Moon.
Solar system (without observing the scales of the Sun and planets and the distances between them).
Lunar eclipses
Of all celestial phenomena People have long been most afraid of lunar and solar eclipses.
On clear sky The moon is shining brightly. Not a cloud around her. And suddenly a dark shadow approaches the shining surface of the Moon from nowhere. More, more... Here it is most of the lunar surface disappeared, and then everything else disappeared. True, it cannot be said that the Moon is not in the sky: it is still visible in the form of a dark purple disk.
A lunar eclipse is explained by the fact that the Moon falls into earth's shadow. If the shadow that the Earth casts from itself covers the Moon entirely, then the so-called full eclipse. And if it does not cover the entire Moon, then a partial lunar eclipse occurs.
A partial eclipse does not make as strong an impression on observers as a total eclipse. After all, the crescent moon is a familiar sight for us.
In the old days, people thought that the Moon was devoured by a terrible monster - a dragon - during an eclipse. Some peoples believed in this so much that they tried to drive away the dragon with the sound of rattles and the roar of drums. And when the Moon appeared in the sky again, people rejoiced: it means that the dragon, frightened by the noise, abandoned its victim.
And in Rus' in the old days, lunar eclipses were considered formidable harbingers of troubles.
In 1248, the chronicler wrote: “There was a sign on the moon: it was all bloody and died... And in the same summer, King Batu moved the army...”
Our ancestors thought that a lunar eclipse predicted the invasion of the Tatar Khan Batu.
How to tell if the crescent moon is growing or shrinking.
In 1471, it was written in the chronicle: “The midnight was unclear, and like blood on the moon and darkness there was a considerable time and again it gradually cleared up..”
Each eclipse was recorded in history as an important event in the life of the people. For a lunar eclipse to occur, the Sun, Earth and Moon must be in one straight line and the Earth must be between the Sun and the Moon. This position of these three luminaries in celestial space is repeated at certain intervals.
Astronomers in ancient times noticed that every 18 years 11 days 8 hours lunar eclipses are repeated in the same order; It is enough to write down the order of eclipses, and you can confidently predict eclipses for the future.
I have already said that in ancient times, astronomers were mainly priests. Having learned to predict eclipses, the priests turned their knowledge to the benefit of religion. They deceived the people, assuring them that the gods themselves were telling them about the approaching eclipse. This is how they supported religious superstitions.
Now the art of predicting eclipses has been perfected high precision, and there is a schedule lunar eclipses for many years to come.
Why do lunar eclipses occur?
Science takes space by storm
Until recently, the possibility of making interplanetary travel seemed so far away... But in space age technology moves quickly, and what seemed impossible yesterday becomes feasible today.
The era of the greats geographical discoveries also did not come immediately. Before setting off in search of distant continents, people discovered coastal islands and, sailing to them, improved their skills.
The same is true with the conquest of space. Among the expanses of the solar system, the Moon is the closest space object, and the path there has already been paved.
Traveling to the Moon will be an excellent school for space flights. But even though the distance between the Earth and the Moon is small (on a cosmic scale), the space separating them has many of the properties of the Big Space.
What if we flew to the moon - in our imagination, of course? What should we use for this? Maybe by plane?
The 384 thousand kilometers separating the Moon from the Earth is not such a long distance. We have planes that fly 2,500 kilometers per hour. This is TU-144. For such an aircraft, 384 thousand kilometers are simply nothing.
Let's do the calculation. Let's divide 384 thousand kilometers by 2500 kilometers. We get about 154 hours of flight, approximately 6.4 days. We need to stock up on enough provisions, water, and most importantly, more fuel for the engine so that there is enough for the return trip.
Fortunately, a large, roomy plane was found. Everything you need has been loaded. We sat down and drove off. How nice it is to be an explorer of world space!
The plane goes up steeply. Here the altitude indicator arrow shows 5, 10, 15 kilometers... Earthly objects are becoming smaller and smaller: rivers seem like thin winding threads, forests - dark spots.
But what is it? Our plane stopped gaining altitude.
What's the matter? - we shout to the pilot.
The air is too thin,” the pilot replies. - The engine can no longer operate normally.
And you're right, of course. You also know how to fly to the moon: on a rocket! Yes, you can only reach the Moon in a rocket, because only a rocket can break the shackles of gravity.
The shackles of gravity... What does this mean?
You push off the floor and jump, but in a split second you're on the floor. The athlete throws a hammer; Having described an arc of several tens of meters, the hammer falls onto the stadium. The anti-aircraft gunners fired at the enemy plane; the shell rose seven to eight kilometers, and its fragments flew back... All bodies of nature are attracted to the Earth.