Each of the 8 planets in our solar system has its own unique characteristics. Some have a dense atmosphere of carbon dioxide or extensive rings, while others orbit the Sun “lying on its side.” We will talk about Uranus and its unusual position, which haunts scientists.
Uranus is the 7th planet in the solar system and belongs to the giant planets. Its average radius is 25,362 kilometers. It is believed that the planet consists mainly of ice: methane, water and ammonia. Hydrogen and helium are present in small quantities, and the planet’s atmosphere consists of them. Uranus has a ring system that is not as pronounced as Saturn's, but is still observable. At the moment, 27 satellites of the planet have been discovered.
Uranus makes one revolution around our star in 84 Earth years, and the period of rotation of the planet around its axis is 17 hours 14 minutes. But the position of this axis of rotation is very unusual. The plane of the planet's equator is inclined to the orbital plane at an angle of 97.86º, that is, it turns out that the planet rotates as if lying on its side and seems to be rolling in its orbit around the Sun.
This unusual location has led to the fact that the change of seasons on Uranus proceeds in a completely special way. At the moment of the solstice, one of the poles of Uranus faces the Sun, and at the equator there is a rapid change of day and night. After six months (that is, after 42 Earth years), the other pole turns towards the Sun. Despite the fact that the polar regions face the Sun for half a year, and the Sun shines very low at the equator, it turned out that the temperature at the equator is higher than at the poles during the “polar day”. Astronomers have not yet been able to figure out what is causing this temperature anomaly.
In addition, scientists have long pondered how it happened that Uranus has such a strange position. There are several versions of how this could have happened. Perhaps Uranus once had a fairly large satellite, under the influence of which its rotation axis underwent such changes. The satellite was lost over time, but the position of the axis remained unchanged. According to another version, at the dawn of the formation of the Solar system, a large celestial body collided with Uranus, which led to the tilt of the rotation axis.
A group of Anglo-American scientists led by astronomer Jacob Kegerray adheres to the same version. They simulated the collision of Uranus with a large object and presented the results of their experiment. Scientists believe that the collision could have occurred about 2-3 billion years ago, at the time of the formation of the planet, when it did not yet have satellites. According to astronomers, the size of the celestial body that collided with Uranus was 2 times greater than the size of our Earth. The impact could lead to a change in the position of the axis, and also affected the structure of the planet itself. As a result of the collision, Uranus lost part of the thermal energy contained in the bowels of the planet, and this can explain the fact that today Uranus is the coldest planet in our solar system. The temperature on its surface drops to minus 224ºС.
URANUS: AROUND THE SUN
"LYING ON YOUR SIDE."
In the 18th century Saturn was considered the boundary of the solar system. It never occurred to anyone that another, unknown planet was hiding behind it. March 13, 1781 a new planet - URANUS – opened by a music teacher from England William Herschel, previously completely unknown in the astronomical world. Noticing a bright disk moving across the sky through his telescope, Herschel mistook it for a comet and reported the discovery of the celestial body to professional astronomers in Greenwich. It became clear quite quickly that this new planet, and news of the discovery spread throughout Europe. The name of the giant planet was given by the German astronomer Johann Bode.
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When people talk about Earth as “the blue planet,” this is an affectionate exaggeration. Distant URANUS turned out to be a truly blue planet.
Comparison of URANUS and EARTH.
The reason for this color lies in the composition of Uranus' atmosphere and its temperature. When it was cold (-218 degrees), the upper layers of the hydrogen-helium atmosphere condensed and now there is a constant presence of methane haze. Methane absorbs red rays well and reflects blue and green ones. That is why Uranus acquired a beautiful aquamarine color.
Uranus' atmosphere is thick, at least 8,000 km thick, and consists of approximately 83% hydrogen, 15% helium and 2% methane.
The planet is barely visible to the naked eye on very clear nights, but is not difficult to spot with a good ground-based telescope. The radius is enormous (diameter 51,800 km): more than 25,000 km, 4 times the radius of the Earth. The mass of Uranus (8.7 x 10 25) is 14.5 times the mass of Earth. Density – 1710 kg/m3. The orbital inclination is 0.77 degrees, and the period of revolution around the Sun is 84.01 years.
Data obtained from Voyager 2 showed that the planet has a small solid iron-rock core, above which a dense atmosphere immediately begins.
Internal structure of URANIUM.
Uranus has almost the same strong magnetic field as Earth, but its configuration is unusual: magnetic pole deviates from the geographic one by almost 60 degrees. So the compass there will not point to the geographic pole.
The sidereal day of Uranus lasts 17 hours 14 minutes. The planet rotates, as they say, “lying on its side” (even slightly “upside down”): the inclination of its rotation axis is 98 degrees. Most planets have an axis of rotation almost perpendicular to the plane of the ecliptic, but Uranus' axis is almost parallel to this plane.
Uranus receives almost 400 times less light than our planet. This corresponds to the illumination on Earth immediately after sunset, at the beginning of twilight.
Under the gas shell there should be a dense ocean of water, ammonia and methane with a surface temperature of 2200 degrees. Atmospheric pressure at ocean level is 200 thousand. earth's atmosphere. The temperature in the core reaches 7000 degrees, and the pressure is 6 million atmospheres.
RINGS OF URANIUM.
A new era in the history of studying the Uranus system began on March 10, 1977. That day, Uranus, moving across the sky, covered a rather bright star with its disk. The instruments recorded nine “blinks” of the star before, and then after, its occultation by the planet. This is how 9 dense, narrow and far apart coal-black rings of Uranus were discovered.
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Subsequently, over 200 occultations of stars by Uranus were observed, as a result of which the properties of its rings were studied and the radii of its rings were refined.
The rings are a set of nine black “webs”. The radii of their orbits lie in the range of 40-50 thousand km, and the width is only 1-10 km, and only the outer ring at its widest part reaches 96 km. Each ring is widest in the part that is farthest from the planet. Their thickness, like the rings of Saturn, is measured in tens of meters.
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the rings are slightly elliptical and inclined to the equatorial plane of Uranus. They have crisp edges and each ring moves almost as one unit. The area between the dense rings is filled with a transparent layer of fine dust.
SATELLITES OF URANIUM .
Before the start of the space age, only 5 satellites of Uranus were discovered. Ten more were discovered in 1986 by Voyager 2. After 1997, astronomers discovered new satellites using ground-based telescopes.
A total of 21 satellites have been discovered.
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In the Uranus satellite system, objects are named after characters in Shakespeare's plays.
Large satellites - TITANIA, OBERON, ARIEL, UMBRIEL.
The two most distant satellites are OBERON And TITANIA , discovered by Herschel, are located at distances of 582.6 and 435.8 million km from the planet. They are almost twins. The diameter of OBERON is 1520 km, and TITANIA is 1580 km. Their radii are approximately half the radius of the Moon.
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external – OBERON
– has an ancient icy surface, heavily pitted with meteorite craters.
OBERON satellite.
On TITANIA
in addition to numerous craters, there is a network of large tectonic faults and signs of ancient volcanism. The walls of some canyons appear light because they are covered with ice.
TITANIA satellite.
The next two satellites - UMBRIEL and ARIEL - were discovered by the English astronomer W. Lascelles in 1851 using a powerful telescope that he built on the island of Malta. These celestial bodies are almost the same size: UMBRIEL, with a diameter of 1170 km, orbits Uranus at a distance of 265 thousand km; ARIEL with a diameter of 1160 km moves in an orbit with a radius of 191 thousand km.
UMBRIEL
– the darkest satellite of the Uranus system, reflecting only 19% of the light incident on it, with a featureless, heavily cratered surface.
UMBRIEL satellite.
ARIEL – the lightest, it reflects 40% of sunlight. On its surface there are traces of large-scale geological movements and clear signs of ancient volcanism. Large craters are almost absent
Satellite ARIEL.
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In 1948, American astronomer Gerard Kuiper first observed the fifth moon of Uranus - MIRANDA
, located at a distance of 130 thousand km from the planet. It is a small satellite (470 km in diameter) with interesting traces of an unexpectedly turbulent geological past: vast furrowed areas reminiscent of plowed fields.
Giant canyons several kilometers deep have been discovered on Miranda.
MIRANDA is a satellite of Uranus.
The celestial bodies located in our galaxy after Saturn have been little studied - space research probes have practically never visited these places. However, earthlings learned something about this region of the solar system. For example, we know which planet rotates while lying on its side.
The tilt of the rotation axis of Uranus
Every planetary body in solar system has its own slope rotational axis, which is the angle between the plane of its equator and the ecliptic - the plane in which the body moves around the star.
But Uranus has a record value - almost 98°. It turns out that this body rotates in a “lying on its side” position, as if rolling along its orbital trajectory.
This phenomenon caused a special change in the Uranian seasons of the year and time of day.
At the time of winter or summer solstice:
- one of the planetary poles “looks” at the Sun;
- in this hemisphere the polar day lasts, in the opposite hemisphere there is a polar night;
- in the equatorial region, day and night quickly alternate;
- an observer at the equator sees the star located extremely low above the horizon, approximately the same as in the polar latitudes on our planet;
- standing at the pole, you can see how the Sun rises almost to the zenith along a spiral trajectory over the course of 21 years, and then spirals down below the horizon for the same number of years.
After local 6 months, during which 42 years will pass on Earth, Uranus will turn to the central luminary of the system with the opposite pole, the situation will be reversed.
The planet also has spring and autumn equinoxes. At these moments, the Sun is almost above the equator, and the result is the cycle of day and night familiar to other planets.
The next equinox - autumn in the southern hemisphere and spring in the northern - began here in 2007 and will last until 2028, when it will be replaced by the winter and summer equinoxes, respectively.
There is some disagreement among scientists about which hemisphere of Uranus is considered northern and which is southern. The unusual position of the celestial body does not allow the poles to be accurately identified. As a result of discussions, it was decided to define them in the same way as on other planets - in relation to the north and south poles of the world.
What caused the tilt of Uranus
There are at least 2 versions of why Uranus lies on its side. Some scientists believe that the planet once had a fairly large natural moon that influenced the Uranian axis of rotation.
Subsequently, the moon collapsed or changed its orbit, but the position of the axis did not change. Opponents of the theory object that today the planet's satellites are tilted along with it. It is difficult to imagine an impact that would tilt both Uranus itself and its satellites.
There is an alternative hypothesis: at the very beginning of the formation solar planets Uranus collided with a large celestial body(presumably with a young rock-ice protoplanet), which caused such an axial tilt. Such a collision could have happened 2-4 billion years ago.
Some astronomers are confident that the impact came out “grazingly” and not “head-on”, otherwise Uranus would have suffered much more destruction or would have completely ceased to exist in its modern form. Others argue that there were multiple collisions because a single impact would have caused other consequences, such as starting to spin in the other direction, but not such a flip.
Although this theory also does not explain why its moons rotated along with the planet, it was confirmed by the results of an experiment conducted by a group of astronomers from the United States and Great Britain. Researcher J. Kegerray and his assistants simulated the collision of a “correctly” rotating Uranus and a large object moving towards it (its dimensions should have been 2 times larger than those of Earth).
This fact not only led to a change in the position of the rotational axis, but also influenced the structure of the planet. The impact caused a significant loss of its thermal energy - it simply burst out of the Uranian depths and dissolved in space.
A second option is also possible: the debris of the collapsing oncoming object fell onto the planet in the form of a thin shell of rock around an ice layer, which isolated the internal planetary heat and caused the object to freeze. This explains why Uranus is now the coldest planetary body in the solar system.
Uranus and its moons as imagined by the artist. Credit: NASA.
As you probably know, Uranus is the seventh planet from the Sun, and the third largest planet in the Solar System. Despite this, we know very little about it, and, unlike Jupiter or Saturn, there is not a single orbital probe there. This is why Uranus is a good target for future space missions.
Uranus is an ice giant that is approximately 4 times more than Earth(Uranus is 50,724 kilometers in diameter and Earth is 12,742 kilometers in diameter) and which has its own set of strange dust rings - possibly formed after the destruction of one of its moons. In total, today we know about 27 satellites of Uranus, and I believe we would learn many interesting and surprising features of this beautiful planet if we sent a space probe there. The sad thing is that a close flyby of Uranus has only been made once - in 1986 - by the Voyager 2 spacecraft.
We've even seen Pluto up close, but NASA or ESA have absolutely no plans to visit Uranus. This is just crazy!
The tilt of the rotation axis of Uranus
Perhaps the most interesting and strange feature of Uranus is its tilt. The planet is literally lying on its side.
In fact, all planets in the Solar System have a certain inclination of the axis of rotation (the angle between the plane of the planet’s orbit and the plane of its equator). For example, the tilt of the Earth's axis is 23.5 degrees, that of Mars is 25 degrees, and even Mercury's rotation axis is tilted by 2.1 degrees. That is, the axes of rotation of all planets are tilted to one degree or another.
However, this parameter for Uranus is a record 97.8 degrees! What could have happened to Uranus?
The collision of a large object twice the size of Earth with Uranus resulted in an unusual tilt of the gas giant's rotation axis. Credit & Copyright: Jacob Kegerreis / Durham University / University of Wisconsin-Madison / W.W. Keck Observatory. The fact that Uranus lies on its side is proof that the calm and measured movement of the planets of the Solar System in their orbits was not always like this. Soon after the formation of the Sun and planets, our system was a rather turbulent place.
At that time, the planets interacted more strongly than they could now even collide and push each other into new orbits. Some planets could shift into more elongated orbits, while others, on the contrary, moved closer to the Sun. Our own Moon may have been formed when an object the size of Mars crashed into Earth. Other satellites were captured by giant planets. It was a real nightmare.
Thus, the solar system you see today is a group of “survivors” - objects that escaped fatal blows.
So what caused the tilt of Uranus?
Today there are two theories. According to the first and dominant theory, the tilt was caused by the collision of Uranus with a small (Earth-sized) planet, and since the planet's satellites do not have such large tilts, the collision occurred shortly after the formation of our system, when Uranus was surrounded only by a disk of gas and dust from which later and satellites were formed. According to the second theory, the tilt was caused massive satellite Uranus, which rocked it for millions of years, and which was then thrown out of our system or collapsed.
However, astronomers believe that the process of shifting the planet's rotation axis was actually more complex, since computer models show that in the event of a single collision the planet would also rotate in reverse direction, but it would turn over completely. Most likely there was a second or even a series of collisions that led to the tilt of Uranus that we see today.
"Southern Ring" and a bright cloud in the north of Uranus. Credit: NASA / ESA / M. Showalter (SETI Institute). Having such a huge tilt of its rotation axis, Uranus is quite different from the other planets in our system. During its 84-year orbital journey, the planet's poles alternately point toward the Sun. Thus, day and night at each pole last 42 Earth years.
Now we are in our calm, orderly solar system, and many do not even think about what cataclysms it experienced in the first few million years of its life.
Uranus is the seventh planet in the solar system and the third gas giant. The planet is the third largest and fourth largest in mass, and received its name in honor of the father of the Roman god Saturn.
Exactly Uranus has the honor of being the first planet discovered in modern history. However, in reality, his initial discovery of it as a planet did not actually happen. In 1781, the astronomer William Herschel while observing stars in the constellation Gemini, he noticed a certain disk-shaped object, which he initially recorded as a comet, which he reported to the Royal Scientific Society of England. However, later Herschel himself was puzzled by the fact that the object’s orbit turned out to be practically circular, and not elliptical, as is the case with comets. It was only when this observation was confirmed by other astronomers that Herschel came to the conclusion that he had actually discovered a planet, not a comet, and the discovery was finally widely accepted.
After confirming the data that the discovered object was a planet, Herschel received the extraordinary privilege of giving it his name. Without hesitation, the astronomer chose the name of King George III of England and named the planet Georgium Sidus, which translated means “George’s Star.” However, the name never received scientific recognition and scientists, for the most part, came to the conclusion that it is better to adhere to a certain tradition in naming the planets of the solar system, namely to name them in honor of the ancient Roman gods. This is how Uranus got its modern name.
Currently, the only planetary mission that has managed to collect information about Uranus is Voyager 2.
This meeting, which took place in 1986, allowed scientists to obtain enough a large number of data about the planet and make many discoveries. Spaceship transmitted thousands of photographs of Uranus, its moons and rings. Although many photographs of the planet showed little more than the blue-green color that could be seen from ground-based telescopes, other images showed the presence of ten previously unknown moons and two new rings. No new missions to Uranus are planned for the near future.
Due to the dark blue color of Uranus, it turned out to be much more difficult to create an atmospheric model of the planet than models of the same or even . Fortunately, images from the Hubble Space Telescope have provided a broader picture. More modern technologies The telescope's visualizations made it possible to obtain much more detailed images than those of Voyager 2. Thus, thanks to Hubble photographs, it was possible to find out that there are latitudinal bands on Uranus, just like on other gas giants. In addition, wind speeds on the planet can reach more than 576 km/hour.
It is believed that the reason for the appearance of a monotonous atmosphere is the composition of its uppermost layer. The visible layers of clouds are composed primarily of methane, which absorbs these observed wavelengths corresponding to the color red. Thus, the reflected waves are represented as blue and green colors.
Beneath this outer layer of methane, the atmosphere consists of approximately 83% hydrogen (H2) and 15% helium, with some methane and acetylene present. This composition is similar to other gas giants in the Solar System. However, Uranus's atmosphere is strikingly different in another way. While the atmospheres of Jupiter and Saturn are mostly gaseous, the atmosphere of Uranus contains much more ice. Evidence of this is the extremely low temperatures on the surface. Considering the fact that the temperature of the atmosphere of Uranus reaches -224 ° C, it can be called the coldest atmosphere in the solar system. In addition, available data indicate that such extremely low temperatures are present around almost the entire surface of Uranus, even on the side that is not illuminated by the Sun.
Uranus, according to planetary scientists, consists of two layers: the core and the mantle. Current models suggest that the core is mainly composed of rock and ice and is about 55 times the mass. The planet's mantle weighs 8.01 x 10 to the power of 24 kg, or about 13.4 Earth masses. In addition, the mantle consists of water, ammonia and other volatile elements. The main difference between the mantle of Uranus and Jupiter and Saturn is that it is icy, albeit not in the traditional sense of the word. The fact is that the ice is very hot and thick, and the thickness of the mantle is 5.111 km.
What is most surprising about the composition of Uranus, and what distinguishes it from the other gas giants of our star system, is that it does not radiate more energy than it receives from the Sun. Given the fact that even , which is very close in size to Uranus, produces about 2.6 times more heat than it receives from the Sun, scientists today are very intrigued by such a weak power generated by Uranus. At the moment, there are two explanations for this phenomenon. The first indicates that Uranus was exposed to volumetric space object in the past, resulting in the loss of most of the planet's internal heat (gained during formation) into outer space. The second theory states that there is some kind of barrier inside the planet that does not allow the internal heat of the planet to escape to the surface.
Orbit and rotation of Uranus
The very discovery of Uranus allowed scientists to almost double the radius of the known Solar System. This means that on average the orbit of Uranus is about 2.87 x 10 to the power of 9 km. The reason for such a huge distance is the duration of passage of solar radiation from the Sun to the planet. It takes about two hours and forty minutes for sunlight to reach Uranus, which is almost twenty times longer than it takes for sunlight to reach Earth. The enormous distance also affects the length of the year on Uranus; it lasts almost 84 Earth years.
The orbital eccentricity of Uranus is 0.0473, which is only slightly less than that of Jupiter - 0.0484. This factor makes Uranus the fourth of all the planets in the Solar System in terms of circular orbit. The reason for such a small eccentricity of Uranus's orbit is that the difference between its perihelion of 2.74 x 10 to the power of 9 km and its aphelion of 3.01 x 109 km is only 2.71 x 10 to the power of 8 km.
The most interesting point about the rotation of Uranus is the position of the axis. The fact is that the axis of rotation for every planet except Uranus is approximately perpendicular to their orbital plane, but Uranus' axis is tilted almost 98°, which effectively means that Uranus rotates on its side. The result of this position of the planet's axis is that North Pole Uranus is on the Sun for half of the planetary year, and the other half is at the planet's south pole. In other words, daytime on one hemisphere of Uranus lasts 42 Earth years, and nighttime on the other hemisphere lasts the same amount. Scientists again cite a collision with a huge cosmic body as the reason why Uranus “turned on its side.”
Considering the fact that the most popular of the rings in our solar system for a long time remained the rings of Saturn, the rings of Uranus could not be discovered until 1977. However, this is not the only reason; there are two more reasons for such a late detection: the distance of the planet from the Earth and the low reflectivity of the rings themselves. In 1986 spacecraft Voyager 2 was able to determine the presence of two more rings on the planet, in addition to those known at that time. In 2005, the Hubble Space Telescope spotted two more. Today, planetary scientists know of 13 rings of Uranus, the brightest of which is the Epsilon ring.
The rings of Uranus differ from Saturn's in almost every way - from particle size to composition. First, the particles that make up the rings of Saturn are small, little more than a few meters in diameter, while the rings of Uranus contain many bodies up to twenty meters in diameter. Second, the particles in Saturn's rings are mostly made of ice. The rings of Uranus, however, are composed of both ice and significant dust and debris.
William Herschel only discovered Uranus in 1781 because the planet was too dim to be seen by ancient civilizations. Herschel himself initially believed that Uranus was a comet, but later revised his opinion and science confirmed the planetary status of the object. Thus, Uranus became the first planet discovered in modern history. The original name proposed by Herschel was "George's Star" - in honor of King George III, but the scientific community did not accept it. The name "Uranus" was proposed by astronomer Johann Bode, in honor of the ancient Roman god Uranus.
Uranus rotates on its axis once every 17 hours and 14 minutes. Like , the planet rotates in a retrograde direction, opposite to the direction of the Earth and the other six planets.
It is believed that the unusual tilt of Uranus's axis could cause a huge collision with another cosmic body. The theory is that a planet supposedly the size of Earth collided sharply with Uranus, which shifted its axis by almost 90 degrees.
Wind speeds on Uranus can reach up to 900 km per hour.
Uranus has a mass of about 14.5 times the mass of Earth, making it the lightest of the four gas giants of our solar system.
Uranus is often referred to as the "ice giant". In addition to hydrogen and helium in its upper layer (like other gas giants), Uranus also has an icy mantle that surrounds its iron core. The upper atmosphere consists of ammonia and icy methane crystals, which gives Uranus its characteristic pale blue color.
Uranus is the second least dense planet in the solar system, after Saturn.
