The influence of the atmosphere of neptune on the temperature regime of the planet. Gas giants neptune and uranium. Size, mass and orbit of the planet Neptune
They are almost like twins: almost the same size, very close masses and rotation periods, very similar composition, thin and weak rings ... There is one more thing that connects them - the history of their discovery.
Mercury or Saturn has been known to people since prehistoric times, in ancient egypt the priests already easily predicted the time and place of their next appearance. But Uranus, although it is quite possible to see it with the naked eye on a clear night, no one noticed. Due to its long orbital period, it moves too slowly relative to the stars for someone to pay attention to it. Moreover, since the invention of the telescope in 1610, astronomers have observed it at least 20 times, recorded its coordinates, sketched it on maps - and still did not notice movement. And only in 1781, William Herschel saw a "foggy star" and began to follow it, checking if it was a comet. So a new planet, Uranus, was first discovered, and soon Pierre Simon Laplace calculated its orbit, so that it could be predicted its movement for many years ahead.
But another half century passed, and it turned out that Uranus was deviating from this orbit! Adams in England and Le Verrier in France independently suggested that another unknown planet was pulling him in and "misleading." They figured out where to look for this invisibility, but Adams didn’t figure it out so accurately and didn’t insist on his results. And Le Verrier, who himself was not an astronomer, went from one observer to another, persuading him to check the place in the sky that he indicated. And in the end, Halle, who had a recently drawn map of this part of the sky, undertook to compare it with what is seen through a telescope - and in the very first hour he found a “star” that had moved from its place. This was Neptune - the first planet, which was first predicted theoretically and only then found. It turns out that people have seen Neptune before - Galileo himself observed it several times through his telescope! - but they also did not notice that it was a planet, not a star.
Compared to Jupiter and Saturn, Uranus and Neptune are some kind of "small size giants". This is because there was not enough gas for them there, far from the Sun - while they were slowly gaining mass, all the gas was "snatched up" by other giant planets, and the remnants scattered into the distance. So the hydrogen and helium on Uranus and Neptune are only 10–20 percent, which is 1–2 Earth masses - not 200 or 80, as on Jupiter or Saturn. But there was quite enough ice for them - it looks like Jupiter helped them here, "tossing pieces" from a more densely filled area closer to the center. (After all, Jupiter was already hooligan and threw everything anywhere.) Moreover, ice is not only ordinary, water, but also ammonia (NH 3) and methane (CH 4). So they are sometimes called ice giants... But here it must be borne in mind that this term is deceiving: what kind of ice is there at such a pressure and at a temperature inside the planet of several thousand degrees! This is not ice, but what it turned into long ago since the fall on the protoplanet - a very hot and very dense liquid, similar to Earth's magma, only consisting of lighter molecules, which smoothly - like on the "hydrogen" giants - turns into gas as it approaches the surface.
So, the core of these planets (from a mixture of metal and stone, and not metallic, as on Earth, and not from metallic hydrogen, as on Jupiter and Saturn) is, according to various estimates, from 0.5 to 3 Earth masses and takes place from the center to 1/5 of the radius, an atmosphere of hydrogen and helium - another 0.5-1.5 of the Earth's mass and the same 1/5 of the radius, but from the outer edge; everything else is a mantle of "ice". The blue color of both planets is believed to be due to the presence of methane in the upper atmosphere, which absorbs the red and reflects the blue rays of the sun.
Task
If both the core and the atmosphere have the same mass (by the same mass of the Earth) and "occupy" 1/5 of the radius, what does it mean that they have the same density?
Answer
Of course not! After all, the volume of a spherical layer depends not only on its thickness, but also on the radius - for example, on a large balloon more rubber is needed, even if the thickness of the ball is the same. (For the same reason, for example, more cardboard will be spent on a large box than on a small cardboard box of the same thickness.) You can compare the volumes of the atmosphere and the core: the volume of a sphere is proportional to its cube radius. This means that the volume of the core is (1/5) 3 = 1/125 of the volume of the planet, and the volume of the atmosphere is 1 - (4/5) 3 = (125 - 64) / 125 ≈ 1/2 the volume of the planet, about 60 times more ... If the masses are equal, then the density of the atmosphere is by the same factor less.
But there are also differences between Uranus and Neptune. The main thing is the direction of rotation. Unlike "normal", that is, slightly tilted Neptune, Uranus "walks lying on its side": its axis of rotation lies almost exactly in the plane of the orbit. Therefore, practically on the entire planet, half a year (that is, 42 of our years!) Lasts a polar day and half a year - a polar night (why so - see "Quantum" No. 6 and No. 7 for 2016). From such a uniform and gradual heating and cooling, the weather on Uranus is very boring: no storms, no hurricanes, not even multi-colored stripes along the equator ... When Voyager 2 flew there, the only spacecraft still approaching Uranus and Neptune , - it was just the height of the polar summer, and he did not manage to see anything interesting. Only in spring and autumn, at least something happens there: recently (the equinox has just passed) a bright cloudy ring appeared (see photo) and at least some whirlwind spots.
Why is the axis of Uranus tilted so? Nobody knows. Indeed, in the cloud from which the planets were formed, everything revolved around the Sun in the same direction - counterclockwise. So the lumps-planets growing in it swirled in the same way. And Uranus (and also Venus) is not. As always in such cases, “they are looking for the guilty one”: maybe Uranus collided with something large, and this is the consequences of the collision. But after such a blow, Venus almost stopped rotating, and Uranus rotates quickly, just in the wrong plane. It is unclear when he could be so crippled: if this happened when Uranus itself was still small, then with further mass gain, it should have greatly slowed down its rotation - after all, everything that fell on it did not rotate the way it did. And if it happened late, when Uranus was already big, then what kind of giant was it supposed to crash into it ?!
Uranus is also the coldest planet, colder than even Neptune, which is a third farther from the Sun: the surface temperature drops to 50 degrees Kelvin (about −225 ° C). And in the center, as astronomers think, it is also lower than that of all giant planets: only 5000 K. (Yes, this is almost like at the edge of the Sun - there are 6000 K. But do not think that this is very much - on Saturn, for example , the temperature inside reaches 12 thousand degrees.) Even Neptune is hotter inside: it radiates into space 2.5 times more heat than it receives from the Sun. Where does the surplus come from? Maybe from the decay of radioactive elements, or maybe from the seepage of heavier helium atoms in a hydrogen atmosphere down, closer to the core. (On Jupiter and Saturn, helium "drowned" long ago, but not on Uranus and Neptune.) Uranus, on the other hand, emits exactly as much as it received, without adding a penny of its energy.
Why is that? Also unknown. Some say that the collision that turned the Uranium axis is again to blame - because of it, the heat was wasted, and Uranus ahead of time cooled down. Others believe that everything is in order with Uranus, that Neptune is too hot for such a distance from the Sun - because of the large satellite, Triton, which "fiddles" with its tidal forces. If so, then the excess energy is "taken away" from Triton, whose orbit is gradually sinking lower and lower.
What else are different between these two planets is satellites. Uranus has satellites, in general, small, together they weigh less than half of one Neptunian Triton, not to mention our Moon. Still, five of them are spherical. Almost all satellites (except for very small cobblestones far from the planet) revolve in the plane of the equator of Uranus - which means that they most likely formed around it, and after the "catastrophe" (and possibly thanks to it - from the resulting building material). All large satellites of Uranus are composed of a mixture of ice (water, dry and ammonia) and rock - roughly equal. Probably, they were previously heated up and "melted", so that the stone sank down, and the ice rose to the surface. In the middle between the two could be an ocean of water, heated by the tides, like the moons of Jupiter and Saturn. In smaller satellites, it froze long ago, and in Titania and Oberon - the two largest - it could have survived to this day. True, the temperature of such "water" is still slightly higher than −100 ° C (!) - it prevents it from freezing great pressure(after all, there is a thick ice shell on top) and non-freezing additives - ammonia and various salts.
All five large satellites are terribly scratched - covered with giant deep canyons hundreds of kilometers long, up to 50 km wide and up to 5 km deep. The largest canyon on Titania stretches from its equator almost to the very pole (1500 km). It is believed that these canyons - huge cracks in the ice crust - were formed during the gradual freezing of the sub-ice ocean: after all, when water freezes, it does not contract (like most substances), but expands. Each new layer of ice "burst" the ice crust and broke it - it is similar to the formation of the scarps of Mercury, only there the crust fell inward, and here it was pushed outward. Perhaps, at the same time, a little water poured out and then flooded the bottom of the cracks.
The satellites of Neptune are completely unlike them. True, they have been very little studied - but it is already clear that Triton alone has a spherical shape. The rest are shapeless lumps, although at least two of them could, judging by the mass, be spherical. Obviously, they never heated up - otherwise they would certainly "melt" into balls. It is unlikely that these satellites formed along with the planet - apparently, they were all captured later.
Triton is 3-4 times lighter than the Moon, takes 7th place in mass among the satellites. In size, it is larger than Pluto, recently stripped of the title of planet, and in other respects it is similar to it. At the same time, it is the only large satellite that revolves around its planet "in the wrong direction" and in a strongly inclined orbit. And this despite the fact that the period of revolution around Neptune is only 6 hours, that is, the orbit is very low! Not otherwise, Triton, like the rest of the Neptune satellites, was not born in these places, but was captured. Where did Neptune manage to get such a large vassal? From the Kuiper belt.
There are only 8 planets, and even ten years ago they said - 9: Pluto was "demoted" into dwarf planets. The fact is that a whole bunch of small planets were discovered behind the orbit of Neptune, some of which are very similar in size and mass to Pluto. In order not to declare them all planets, I had to come up with a separate category for them - dwarf planets... A cluster of dwarf planets and small bodies beyond the orbit of Neptune, at distances of 30-50 AU. that is, it is called Kuiper belt, by analogy with the asteroid belt. By the way, the largest body from the asteroid belt - Ceres - was also transferred from asteroids to the category of dwarf planets. And, like Jupiter in the asteroid belt, Neptune establishes its own order in the Kuiper belt, disturbing and swinging the orbits of some planets and stabilizing the orbits of others. Almost the entire Kuiper belt is in resonance with it: for example, the orbital periods of Neptune and Pluto are 2: 3. Their orbits almost intersect, but they will never collide precisely because of the resonance.
Returning to Triton, we note that Neptune has already managed to "educate" him - Triton rotates synchronously (all the time "looks" at the planet with one side). Remarkably, its orbit is a perfect circle. Obviously, earlier it was elongated (although it is not known how much), and quite a lot of energy had to be spent on its "alignment" by tidal forces. This energy, turning into heat, heated Triton, and cryovolcanoes still operate on it, which, instead of hot magma, spew liquid nitrogen. It is possible that there is still an unfrozen liquid under the surface (water with ammonia at −100 ° C). At the same time, it is so cold on the surface of Triton (−235 ° C) that nitrogen, which in terrestrial conditions is only a gas, can even fall out there in the form of snow.
Both Uranus and Neptune are surrounded by rings, but these rings are weak and consist of dark particles - the view is not at all the same as that of Saturn. By how thin they are and how wide the gaps are between them (see photo), it seems that these are the remains of small satellites recently destroyed by tidal forces.
So our journey to the eight large planets of the solar system and their moons has come to an end. But the secrets and mysteries of the solar system, of course, do not end there ...
Artist Maria Useinova
If you are going to spend a vacation on another planet, it is important to learn about possible climatic changes :) But seriously, many people know that most of the planets in our solar system have extreme temperatures that are not suitable for quiet living. But what exactly are the temperatures on the surface of these planets? Below I offer a small overview of the temperatures of the planets in the solar system.
Mercury
Mercury is the planet closest to the Sun, so one would assume that it is constantly glowing like an oven. However, while the temperature on Mercury can reach 427 ° C, it can also drop to a very low -173 ° C. Such a large difference in temperature of Mercury occurs because it has no atmosphere.
Venus
Venus, the second closest planet to the Sun, has the highest average temperatures of any other planet in our solar system, with temperatures regularly reaching 460 ° C. Venus is so hot because of its proximity to the Sun and its dense atmosphere. The atmosphere of Venus is composed of dense clouds containing carbon dioxide and sulfur dioxide. This creates a strong greenhouse effect that traps the sun's heat in the atmosphere and turns the planet into a furnace.
Earth
Earth is the third planet from the Sun and is still the only planet known for its ability to support life. The average temperature on Earth is 7.2 ° C, but it varies with large deviations from this indicator. The highest temperature ever recorded on Earth was 70.7 ° C in Iran. The most low temperature was, and it reaches -91.2 ° C.
Mars
Mars is cold because, firstly, it does not have an atmosphere to maintain high temperatures, and secondly, it is located relatively far from the Sun. Since Mars has an elliptical orbit (it gets much closer to the Sun at some points in its orbit), during the summer its temperatures can deviate by 30 ° C from normal in the northern and southern hemispheres. The minimum temperature on Mars is approximately -140 ° C, and the highest is 20 ° C.
Jupiter
Jupiter does not have any solid surface, as it is a gas giant, so it does not have any surface temperature either. At the top of Jupiter's clouds, the temperature is about -145 ° C. As you descend closer to the center of the planet, the temperature increases. At a point where atmospheric pressure is ten times that of Earth, the temperature is 21 ° C, which some scientists jokingly call "room temperature." In the core of the planet, temperatures are much higher, reaching around 24,000 ° C. For comparison, it's worth noting that Jupiter's core is hotter than the Sun's surface.
Saturn
As with Jupiter, the temperature in the upper atmosphere of Saturn remains very low - down to about -175 ° C - and increases as it approaches the center of the planet (up to 11,700 ° C at the core). Saturn actually generates heat itself. It generates 2.5 times more energy than it receives from the Sun.
Uranus
Uranus is the coldest planet with the lowest recorded temperature of -224 ° C. Although Uranus is far from the Sun, this is not the only reason for its low temperatures. All other gas giants in our solar system emit more heat from their cores than they receive from the sun. Uranus has a core with a temperature of approximately 4737 ° C, which is only one-fifth of the temperature of Jupiter's core.
Neptune
With temperatures as high as -218 ° C in Neptune's upper atmosphere, this planet is one of the coldest in our solar system. Like the gas giants, Neptune has a much hotter core, which is around 7000 ° C.
Below is a graph showing planetary temperatures in both Fahrenheit (° F) and Celsius (° C). Please note that since 2006 Pluto does not fall under the classification of planets (see.
March 13, 1781 William Herschel (1738-1822), using a homemade telescope, accidentally discovered a new planet. Herschel was a musician living in Bath, England, where he worked as an organist. Astronomy was his favorite hobby. He made a telescope himself and compiled a list of binary stars that, when observed, appeared to be very close to each other. One night, he noticed a new object, which he mistook for a comet, as it slowly shifted relative to the stars. However, after a few weeks it became clear that this was not a comet, but a new planet in our solar system.
Herschel's discovery made him famous all over the world, and King George III appointed him a royal pension. At first, astronomers could not choose a name for the new planet, but in the end they called it Uranus. According to classical mythology, Uranus is Jupiter's grandfather.
Another new planet, Neptune, was discovered in 1846 as a result of careful, systematic searches. For many years, it has puzzled astronomers that Uranus is constantly deviating from its path. Based on Newton's law of universal gravitation, they calculated where Uranus should be, but each time they found that its true position in the sky did not coincide with the theoretical one. Scientists understood that this could happen if Uranus is exposed to powerful gravitational forces from some unknown planet.
The two mathematicians set to work calculating the location of the mysterious planet. In 1845, in Cambridge, England, John Couch Adams (1819-1892) joined forces with James Challis (1803-1862). They worked together at the University of Cambridge Observatory. Although Challis actually recorded, recorded this new planet, he himself did not realize that he had found it! At almost the same time, the French astronomer Urbain Le Verrier (1811-1877) was trying to convince scientists at the Paris Observatory in France to start searching for an invisible planet. For the same purpose, he wrote a letter to the Berlin Observatory in Germany. On the very night that Johann Halle received this letter (September 23, 1846), he discovered the predicted planet in the very place that Le Verrier had determined by calculation. The planet was named Neptune after the ancient Roman sea god.
Uranus - an overturned planet
Uranus is composed primarily of hydrogen and helium, but one-seventh of its atmosphere is methane. Methane makes Uranus appear bluish, a fact first noted by Herschel. The Voyager 2 space probe has found only a few cloud strips in the upper atmosphere of Uranus. The temperature of this planet is approximately -220 ° C. At the center of Uranus is a large core made of stone and iron.
The proper axis of rotation of Uranus is tilted more than at a right angle, which means that its north pole is below the plane of its orbit. This is a unique phenomenon in the entire solar system. Uranus bypasses its orbit around the Sun in 84 years. The seasons on this planet appear to be very unusual. For about 20 years, the north pole is more or less facing the sun, while the south pole is constantly in darkness.
Astronomers speculate that Uranus collided with another major planet shortly after the formation of the solar system. It is possible that as a result of this collision, Uranus was overturned on its side.
Rings around Uranus
The rings of Uranus were discovered by chance. Astronomers wanted to know more about the atmosphere of this planet. As Uranus passed in front of one faint star, they noticed that the star blinked several times before and after Uranus completely covered it. No one foresaw this phenomenon, and the reason for it was that Uranus had at least nine weakly expressed rings orbiting this planet. The rings of Uranus are composed of large and small stones, as well as fine dust.
Miranda
Five large moons and ten small ones revolve around Uranus. The most amazing of them is Miranda, about 500 km across. Its surface amazes with a variety of valleys, gorges and steep cliffs. It seems that this moon is fused from three or four huge stone debris. Perhaps they are the remnants of a former moon that once collided with an asteroid, and now has managed to reassemble its debris.
Voyager 2 Neptune
Voyager 2 flew past Neptune on August 24, 1989, after a 12-year journey to this planet, and the information it obtained presented us with numerous surprises. Since Neptune is 30 times farther from the Sun than Earth, sunlight reaching its surface is extremely weak, and the temperature on Neptune is -213 ° C. However, it is slightly warmer here than on Uranus, although Uranus is closer to the Sun. This is because Neptune has internal source thermal energy, which gives three times more heat than the planet receives from the sun.
A variety of weather events take place in the atmosphere of Neptune. Voyager 2 observed a Great Dark Spot there, similar, apparently, to Jupiter's Great Red Spot. There are also thin cirrus clouds. Some of them are composed of frozen methane.
Voyager 2 is now racing towards the edge of the solar system. It will not come close to Pluto, the last planet, but astronomers will be able to maintain radio contact with the ship until at least 2020. During this time, Voyager 2 will send information to Earth about gas and dust in the distant regions of the solar system.
Triton
Neptune has a satellite larger than the Earth's Moon: Triton. Like Earth, Triton has a nitrogenous atmosphere, and it is seven-tenths of solid rock and three-tenths of water. Near the south pole of Triton, Voyager 2 took pictures of red ice, and at the equator, it photographed blue ice from frozen methane.
Triton has huge rocks cut by water ice, as well as countless craters. Neptune changes the direction of motion of comets entering the solar system from outside. It is possible that some of them collided with Triton, and as a result of these collisions its craters appeared. Triton has dark stripes of volcanic origin. Scientists believe that LSD, composed of frozen water, methane and nitrogen, was spewed from the depths of Triton through volcanoes.
- 1690 Uranus was first described, but as a star.
- 1781 Uranus is discovered as a planet by William Herschel.
- 1787 William Herschel discovers two moons of Uranus.
- 1846 Discovery of Neptune. 1977 The rings of Uranus are discovered.
- 1986 Rapprochement of Voyager 2 with Uranus. New moons of Uranus are discovered.
- 1989 Voyager 2 passes near Neptune, opens rings.
IMPORTANT DISCOVERIES
Neptune as seen from Voyager 2
According to scientists, Neptune is one of the coldest places in the solar system. The temperature of the planet's upper cloud layer (where the pressure is 0.1 bar) can drop to 55 degrees Kelvin. It is -218 degrees Celsius.
Neptune temperature
The average temperature of the atmosphere, at the level where the pressure is 1 bar (which is approximately equal to the pressure of 1 atmosphere, as at the surface of the Earth), is 73 K (-200 Celsius).
But there is one strange anomaly at the planet's south pole. It is 10 degrees warmer than in other parts of the giant. This so-called " hot spot"Appeared because the South Pole is currently facing the Sun. As you move in orbit, the illumination of different regions changes. Over time, the North Pole will become warmer and the South Pole will cool down.
If we make a virtual trip to the center of the planet, we will find that its heating increases sharply with depth. As with all planets, the temperature of the inner layers is much higher than at the surface.
The core temperature is 7000 degrees Celsius, which is slightly higher than the surface of the Sun.
The huge temperature difference between the center and its surface creates huge storms. The speed of the winds is about 2100 km / h, which makes them the fastest in the solar system.
What is the temperature of the planet compared to other objects in the solar system? Pluto is only 33 Kelvin, colder than Neptune. But Pluto is no longer a planet, so it may not be the coldest planet in the solar system. On Uranus, the temperature of the cloud layer (at a pressure of 1 bar) averages 76 Kelvin. Other planets are much warmer, up to +425 degrees Celsius on the surface of Mercury.
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Neptune is the eighth and farthest planet in the solar system. Neptune is also the fourth largest planet in diameter and the third largest planet. The mass of Neptune is 17.2 times, and the diameter of the equator is 3.9 times that of the Earth. The planet was named after the Roman god of the seas.
Discovered on September 23, 1846, Neptune became the first planet discovered through mathematical calculations rather than regular observation. The discovery of unforeseen changes in the orbit of Uranus gave rise to the hypothesis of an unknown planet, the gravitational disturbing influence of which they are due. Neptune was found within the predicted position. Soon, its satellite Triton was also discovered, but the other 13 satellites, now known, were unknown until the 20th century. Neptune was visited by only one spacecraft, Voyager 2, which flew close to the planet on August 25, 1989.
Neptune is similar in composition to Uranus, and both planets differ in composition from the larger giant planets - Jupiter and Saturn. Sometimes Uranus and Neptune are placed in a separate category of "ice giants". The atmosphere of Neptune, like the atmosphere of Jupiter and Saturn, consists mainly of hydrogen and helium, along with traces of hydrocarbons and possibly nitrogen, but contains a higher proportion of ice: water, ammonia, methane. The core of Neptune, like Uranus, consists mainly of ice and rocks. Traces of methane in the outer layers of the atmosphere, in particular, cause of blue color planets.
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| Discovery of the planet: | |
| Discoverer | Urbain Le Verrier, Johann Halle, Heinrich d'Arre |
| Opening place | Berlin |
| opening date | September 23, 1846 |
| Detection method | payment |
| Orbital characteristics: | |
| Perihelion | 4 452 940 833 km (29.76607095 AU) |
| Aphelion | 4,553,946,490 km (30.44125206 AU) |
| Semi-major axis | 4 503 443 661 km (30.10366151 AU) |
| Orbital eccentricity | 0,011214269 |
| Sidereal period of circulation | 60 190.03 days (164.79 years) |
| Synodic period of circulation | 367.49 days |
| Orbital speed | 5.4349 km / s |
| Average anomaly | 267.767281 ° |
| Mood | 1.767975 ° (6.43 ° relative to the solar equator) |
| Ascending node longitude | 131.794310 ° |
| Pericenter argument | 265.646853 ° |
| Satellites | 14 |
| Physical characteristics: | |
| Polar compression | 0.0171 ± 0.0013 |
| Equatorial radius | 24,764 ± 15 km |
| Polar radius | 24 341 ± 30 km |
| Surface area | 7.6408 10 9 km 2 |
| Volume | 6.254 10 13 km 3 |
| Weight | 1.0243 10 26 kg |
| Medium density | 1.638 g / cm 3 |
| Free fall acceleration at the equator | 11.15 m / s 2 (1.14 g) |
| Second space speed | 23.5 km / s |
| Equatorial rotation rate | 2.68 km / s (9648 km / h) |
| Rotation period | 0.6653 days (15 h 57 min 59 s) |
| Axis tilt | 28.32 ° |
| Right ascension of the north pole | 19h 57m 20s |
| Declination of the north pole | 42.950 ° |
| Albedo | 0.29 (Bond), 0.41 (geom.) |
| Apparent magnitude | 8.0-7.78m |
| Corner diameter | 2,2"-2,4" |
| Temperature: | |
| 1 bar level | 72 K (about -200 ° C) |
| 0.1 bar (tropopause) | 55 C |
| Atmosphere: | |
| Composition: | 80 ± 3.2% hydrogen (H 2) 19 ± 3.2% helium 1.5 ± 0.5% methane about 0.019% hydrogen deuteride (HD) approximately 0.00015% ethane |
| Ice: | ammonia, water, hydrosulfide-ammonium (NH 4 SH), methane |
| PLANET NEPTUNE | |
The strongest winds among the planets of the solar system rage in the atmosphere of Neptune, according to some estimates, their speeds can reach 2100 km / h. During the flyby of Voyager 2 in 1989, the so-called Great Dark Spot was discovered in the southern hemisphere of Neptune, similar to the Great Red Spot on Jupiter. The temperature of Neptune in the upper atmosphere is close to -220 ° C. In the center of Neptune, the temperature is, according to various estimates, from 5400 K to 7000-7100 ° C, which is comparable to the temperature on the surface of the Sun and is comparable to the internal temperature of most of the known planets. Neptune has a weak and fragmented ring system, possibly discovered back in the 1960s, but only reliably confirmed by Voyager 2 in 1989.
July 12, 2011 marks exactly one Neptunian year - or 164.79 Earth years - since the discovery of Neptune on September 23, 1846.
Physical characteristics:
With a mass of 1.0243 · 10 26 kg, Neptune is an intermediate link between the Earth and the large gas giants. Its mass is 17 times that of Earth, but is only 1/19 of the mass of Jupiter. The equatorial radius of Neptune is 24,764 km, which is almost 4 times larger than the Earth's. Neptune and Uranus are often considered a subclass of gas giants called "ice giants" due to their smaller size and lower concentration of volatiles.
The average distance between Neptune and the Sun is 4.55 billion km (about 30.1 average distances between the Sun and the Earth, or 30.1 AU), and it takes 164.79 years to complete a revolution around the Sun. The distance between Neptune and Earth is 4.3 to 4.6 billion km. On July 12, 2011, Neptune completed its first full revolution since the discovery of the planet in 1846. From the Earth, it was seen differently than on the day of the discovery, as a result of the fact that the period of the Earth's revolution around the Sun (365.25 days) is not a multiple of the period of Neptune's revolution. The planet's elliptical orbit is tilted 1.77 ° relative to the Earth's orbit. Due to the presence of an eccentricity of 0.011, the distance between Neptune and the Sun changes by 101 million km - the difference between perihelion and aphelion, that is, the nearest and most distant points of the planet's position along the orbital path. The axial tilt of Neptune is 28.32 °, which is similar to the tilt of the axis of the Earth and Mars. As a result, the planet experiences similar seasonal changes. However, due to Neptune's long orbital period, the seasons last for about forty years each.
The sidereal rotation period for Neptune is 16.11 hours. Due to the axial tilt similar to that of the Earth (23 °), changes in the sidereal period of rotation during its long year are not significant. Since Neptune has no solid surface, its atmosphere is subject to differential rotation. The wide equatorial zone rotates with a period of approximately 18 hours, which is slower than the 16.1 hour rotation of the planet's magnetic field. In contrast to the equator, the polar regions rotate in 12 hours. Among all the planets of the solar system, this type of rotation is most pronounced precisely in Neptune. This leads to a strong latitudinal wind shear.
Neptune has a great influence on the Kuiper belt, which is very distant from it. The Kuiper Belt is a ring of icy minor planets, similar to the asteroid belt between Mars and Jupiter, but much longer. It ranges from the orbit of Neptune (30 AU) to 55 astronomical units from the Sun. The gravitational force of gravity of Neptune has the most significant effect on the Kuiper belt (including in terms of the formation of its structure), comparable in proportion to the influence of the force of gravity of Jupiter on the asteroid belt. During the existence of the solar system, some regions of the Kuiper belt have been destabilized by the gravity of Neptune, and gaps have formed in the structure of the belt. An example is the region between 40 and 42 AU. e.
The orbits of objects that can be held in this belt for a sufficiently long time are determined by the so-called. secular resonances with Neptune. For some orbits, this time is comparable to the entire lifetime of the solar system. These resonances appear when the orbital period of an object around the Sun is related to the orbital period of Neptune as small natural numbers, for example, 1: 2 or 3: 4. Thus, objects mutually stabilize their orbits. If, for example, an object revolves around the Sun twice as slow as Neptune, then it will go exactly half the way, while Neptune will return to its original position.
The most densely populated part of the Kuiper belt, which includes more than 200 known objects, is in a 2: 3 resonance with Neptune. These objects make one revolution every 1 1/2 of Neptune's orbits and are known as "plutino" because they include one of the largest Kuiper belt objects, Pluto. Although the orbits of Neptune and Pluto come very close to each other, the 2: 3 resonance will prevent them from colliding. In other, less "populated" areas, there are resonances 3: 4, 3: 5, 4: 7 and 2: 5.
At its Lagrange points (L4 and L5) - zones of gravitational stability - Neptune holds many Trojan asteroids, as if dragging them along its orbit. The Trojans of Neptune are with him in a 1: 1 resonance. Trojans are very stable in their orbits, and therefore the hypothesis of their capture by the gravitational field of Neptune is doubtful. Most likely, they formed with him.
Internal structure
The internal structure of Neptune resembles the internal structure of Uranus. The atmosphere makes up about 10-20% of the total mass of the planet, and the distance from the surface to the end of the atmosphere is 10-20% of the distance from the surface to the core. The pressure near the core can reach 10 GPa. Volume concentrations of methane, ammonia and water found in the lower atmosphere
Gradually, this darker and hotter region is compacted into a superheated liquid mantle, where temperatures reach 2000-5000 K. The mass of Neptune's mantle is 10-15 times greater than that of the Earth, according to various estimates, and is rich in water, ammonia, methane and other compounds. According to the terminology generally accepted in planetary science, this matter is called icy, even though it is a hot, very dense liquid. This highly conductive liquid is sometimes called the ocean of aqueous ammonia. At a depth of 7000 km, conditions are such that methane decomposes into diamond crystals that "fall" onto the core. According to one hypothesis, there is a whole ocean of "diamond liquid". Neptune's core is composed of iron, nickel and silicates and is believed to have a mass 1.2 times that of Earth. The pressure in the center reaches 7 megabars, that is, about 7 million times more than on the surface of the Earth. The temperature in the center may be as high as 5400 K.
Atmosphere and climate
Hydrogen and helium were found in the upper layers of the atmosphere, which make up 80 and 19%, respectively, at a given altitude. Traces of methane are also observed. Noticeable absorption bands of methane are found at wavelengths above 600 nm in the red and infrared part of the spectrum. As in the case of Uranus, the absorption of red light by methane is the most important factor in giving the atmosphere of Neptune a blue tint, although Neptune's bright azure differs from the more moderate aquamarine color of Uranus. Since the methane content in the atmosphere of Neptune is not very different from that in the atmosphere of Uranus, it is assumed that there is also a certain, as yet unknown, atmospheric component that contributes to the formation of blue. Neptune's atmosphere is subdivided into 2 main regions: the lower troposphere, where temperature decreases with altitude, and the stratosphere, where temperature increases with altitude. The border between them, the tropopause, is at a pressure of 0.1 bar. The stratosphere is replaced by the thermosphere at a pressure level lower than 10 -4 - 10 -5 microbar. The thermosphere gradually passes into the exosphere. Models of the Neptune troposphere suggest that depending on the height, it consists of clouds of variable compositions. The upper level clouds are in a pressure zone below one bar, where the temperature favors the condensation of methane.
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Methane on Neptune
The false color image was captured by the Voyager 2 spacecraft using three filters: blue, green, and a filter that shows the absorption of light by methane. Thus, regions in the image that have bright White color or a red tint contain a high concentration of methane. All of Neptune is covered by the ubiquitous methane fog in the translucent layer of the planet's atmosphere. In the center of the planet's disk, light passes through the haze and goes deeper into the planet's atmosphere, as a result of which the center appears less red, and at the edges of the methane fog scatters sunlight at high altitudes, as a result of which a bright red halo forms. |
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At pressures between one and five bar, clouds of ammonia and hydrogen sulfide form. At pressures over 5 bar, clouds can be composed of ammonia, ammonium sulfide, hydrogen sulfide and water. Deeper, at a pressure of approximately 50 bar, clouds of water ice can exist at temperatures as low as 0 ° C. Also, it is possible that clouds of ammonia and hydrogen sulfide can be found in this area. Neptune's high-altitude clouds were observed by casting shadows on the opaque cloud layer below. Among them, cloud stripes stand out, which "wrap" around the planet at a constant latitude. These peripheral groups have a width of 50-150 km, and they themselves are 50-110 km above the main cloud layer. A study of Neptune's spectrum suggests that its lower stratosphere is clouded by condensation of ultraviolet methane photolysis products such as ethane and acetylene. Traces of hydrogen cyanide and carbon monoxide.
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High-altitude cloud stripes on Neptune
The image was taken by the Voyager 2 spacecraft two hours before the closest approach to Neptune. The vertical bright stripes of Neptune's clouds are clearly visible. These clouds were observed at a latitude of 29 degrees north near the eastern terminator of Neptune. Clouds cast shadows, which means they are higher than the main opaque cloud layer. Image resolution 11 km per pixel. The width of the bands of clouds is from 50 to 200 km, and the shadows cast by them extend for 30-50 km. The height of the clouds is about 50 km. |
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The stratosphere of Neptune is warmer than the stratosphere of Uranus due to the higher concentration of hydrocarbons. For unclear reasons, the planet's thermosphere has an abnormally high temperature of about 750 K. For such a high temperature, the planet is too far from the Sun for it to warm up the thermosphere with ultraviolet radiation. Perhaps this phenomenon is a consequence of atmospheric interaction with ions in the planet's magnetic field. According to another theory, the basis of the heating mechanism is gravity waves from the inner regions of the planet, which are scattered in the atmosphere. The thermosphere contains traces of carbon monoxide and water that got there, possibly from external sources such as meteorites and dust.
One of the differences between Neptune and Uranus is the level of meteorological activity. Voyager 2, flying near Uranus in 1986, recorded extremely weak atmospheric activity. In contrast to Uranus, Neptune experienced noticeable weather changes during the 1989 Voyager 2 survey.
The weather on Neptune is characterized by an extremely dynamic storm system, with winds reaching near supersonic speeds (about 600 m / s). In the course of tracking the movement of permanent clouds, a change in wind speed was recorded from 20 m / s in the east direction to 325 m / s in the west. In the upper cloud layer, wind speeds vary from 400 m / s along the equator to 250 m / s at the poles. Most winds on Neptune blow in the opposite direction of the planet's rotation on its axis. General scheme winds shows that at high latitudes the direction of the winds coincides with the direction of rotation of the planet, and at low latitudes it is opposite to it. Differences in the direction of air currents are believed to be due to the "skin effect" rather than any deep atmospheric processes. The content of methane, ethane, and acetylene in the atmosphere in the equatorial region exceeds by tens and hundreds of times the content of these substances in the region of the poles. This observation can be considered evidence in favor of the existence of an upwelling at the equator of Neptune and its decrease closer to the poles.
In 2006, the upper troposphere of Neptune's south pole was observed to be 10 ° C warmer than the rest of Neptune, where temperatures averaged -200 ° C. This difference in temperature is enough for methane, which is frozen in other regions of Neptune's upper atmosphere, to seep into space at the South Pole. This "hot spot" is a consequence of the axial tilt of Neptune, the south pole of which is already a quarter of the Neptunian year, that is, about 40 Earth years, facing the Sun. As Neptune slowly orbits towards the opposite side of the Sun, the South Pole will gradually recede into the shadows, and Neptune will substitute the North Pole for the Sun. Thus, the release of methane into space will move from the south pole to the north. Due to seasonal changes, cloud bands in the southern hemisphere of Neptune have been observed to increase in size and albedo. This trend was noticed back in 1980, and is expected to continue until 2020 with the onset of a new season on Neptune. The seasons change every 40 years.
In 1989, NASA's Voyager 2 discovered the Great Dark Spot, a stable anticyclone storm measuring 13,000 x 6600 km. This atmospheric storm resembled Jupiter's Great Red Spot, but on November 2, 1994, the Hubble Space Telescope did not detect it in its original location. Instead, a new, similar formation was discovered in the northern hemisphere of the planet. The scooter is another storm found south of the Great Dark Spot. Its name is a consequence of the fact that even a few months before the rapprochement of Voyager 2 with Neptune, it was clear that this group of clouds was moving much faster than the Great Dark Spot. Subsequent images revealed groups of clouds even faster than the scooter.
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Big dark spot
The photograph on the left was taken by Voyager 2's narrow-angle camera using a green and orange filter, from 4.4 million miles from Neptune, 4 days and 20 hours before closest approach to the planet. The Great Dark Spot and its smaller companion in the west, the Lesser Dark Spot, are clearly visible. The series of images on the right shows changes in the Great Dark Spot over 4.5 days during the approach of the Voyager 2 spacecraft, the shooting interval is 18 hours. The large dark spot is at 20 degrees south latitude and spans up to 30 degrees longitude. The upper image in the series was taken at a distance of 17 million km from the planet, the lower one - 10 million km. A series of images showed that the storm changes over time. In particular, in the west, at first, a dark plume stretched behind the BTP, which then pulled into the main area of the storm, leaving behind a series of small dark spots - "beads". A large bright cloud on the southern border of the BTP is a more or less permanent companion of the formation. The apparent movement of small clouds at the periphery suggests counterclockwise rotation of the BTP. |
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The Lesser Dark Spot, the second-most intense storm seen during Voyager 2's rapprochement with the planet in 1989, lies further south. Initially it appeared to be completely dark, but as it got closer, the bright center of the Small Dark Spot became more visible, as can be seen in most clear high-resolution photographs. Neptune's "dark spots" are thought to originate in the troposphere at lower altitudes than the brighter, more visible clouds. Thus, they appear to be a kind of holes in the upper cloud layer, as they open up gaps that allow you to see through the darker and deeper layers of the clouds.
Because these storms are persistent and can last for months, they are thought to have a vortex structure. Often associated with dark spots are brighter, persistent methane clouds that form in the tropopause. The persistence of accompanying clouds indicates that some of the former "dark spots" can continue to exist as a cyclone, even though they lose their dark color. Dark spots can dissipate if they move too close to the equator or through some other unknown mechanism.
The more varied weather on Neptune compared to Uranus is believed to be a consequence of the higher internal temperature. At the same time, Neptune is one and a half times more distant from the Sun than Uranus, and receives only 40% of the amount of sunlight that Uranus receives. The surface temperatures of these two planets are approximately equal. The upper troposphere of Neptune reaches a very low temperature of -221.4 ° C. At a depth of 1 bar, the temperature reaches -201.15 ° C. Gases go deeper, but the temperature is steadily increasing. As with Uranus, the heating mechanism is unknown, but the discrepancy is large: Uranus emits 1.1 times more energy than it receives from the Sun. Neptune emits 2.61 times more than it receives, its internal heat source adds 161% to the energy received from the Sun. Although Neptune is the planet farthest from the Sun, its internal energy is sufficient to generate the fastest winds in the solar system.
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A new dark spot
The Hubble Space Telescope has discovered a new large dark spot located in the northern hemisphere of Neptune. The tilt of Neptune and its current position almost do not allow us to see more details now, as a result, the spot in the image is located near the limb of the planet. The new spot mimics a similar storm in the southern hemisphere that was discovered by Voyager 2 in 1989. In 1994, images from the Hubble Telescope showed that the spot in the southern hemisphere had disappeared. Like its predecessor, the new storm is surrounded by clouds at the border. These clouds are created when gas from the lower regions rises up and then cools to form methane ice crystals. |
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Several possible explanations have been proposed, including radiogenic heating by the planet's core (similar to the heating of the Earth by radioactive potassium-40), the dissociation of methane into other chain hydrocarbons in the atmosphere of Neptune, and convection in the lower atmosphere, which leads to deceleration of gravitational waves over the tropopause.
