Ten secrets of the solar system

Today, although human beings have extended their tentacles to explore the universe to planetary systems outside the solar system, they still know little about some mysteries of the solar system home. However, with the help of various detectors in space, "the Eight Immortals cross the sea and show their magical powers", the secrets of the careful protection of the solar system may be revealed by us one by one.

1 Unique solar system

Little people come first, little people come last! The planets in the solar system seem to be arranged according to size. First, close to the sun are terrestrial planets: Mercury, Venus, Earth and Mars. They are mainly composed of silicate rocks with small volume and mass, and are also called rocky planets. Secondly, the planets farther away from the sun are woody planets: Jupiter, Saturn, Uranus and Neptune. They are huge in size and mass, usually gaseous, also known as gas giant planets. Therefore, astrophysicists believe that if there are other "solar systems" (that is, other celestial systems similar to our solar system), its planets must be arranged in this way, and they will faithfully revolve around their stars while rotating. ...

However, this is not the case! 1995 The first batch of extrasolar planets discovered soon revealed the truth: unlike the situation in our solar system, the nearest stars are just gas giants. They are strongly radiated by stars, resulting in high surface temperature, so they are also called "hot Jupiter". Their orbits are very close to the orbits of their stars, and they are all close to perfect circles!

Astrophysicists are quite surprised that the actual situation is so different from the original idea. To sum up briefly: Earth-like planets are rocky planets, close to the sun, made of so-called refractory materials, which can withstand the powerful heat released by the early sun; Woodlike planets are gas giants, far from the sun, mainly composed of ice and gas, and receive relatively little solar radiation. In our solar system, gas giant planets are far away from the sun. In short, in this model, there is no hot Jupiter!

Next, astrophysicists try to establish some mathematical models to simulate the formation of other "solar systems" and seek solutions to the equations in the models. They successfully found that in other "solar systems", although gas giant planets were formed far away from their parent stars (similar to the situation in our solar system), they did not stay where they were, but were forced to "leave their homes". This is because they are slowed down by the dust and gas in the protoplanetary disk (that is, the dense gas around the newly formed young stars), and gradually lose energy, making it increasingly difficult to resist the gravity of their stars. Therefore, these gas giant planets slowly move towards their sun along huge spiral orbits until they reach their present positions. Next, will they continue this journey of moths to the fire? For some gas giant planets, the answer is yes: according to the observations of astrophysicists, a gas giant planet is being swallowed up by its star!

I see. So why didn't the gas giant planets in our solar system suffer the same fate? It should be said that the solar system is lucky. When these gas giant planets formed, the dust and gas in the protoplanetary disk disappeared, so these "lucky" can stay where they are! However, this is only a special case after all, and the situation of star systems like the "solar system" is varied.

There are creatures lurking in the atmosphere of Venus?

Cyclones, tornadoes and snowstorms on the earth have brought great pain to mankind. However, compared with the disastrous weather on Venus, they are nothing! Imagine: near the equator, the wind with a speed of up to 400 km/h whizzes past the clouds, bringing a sulfuric acid rain that can turn you into paste; A huge double cyclone (five times the size of the cyclone on earth) rages in the Antarctic region of Venus, and its cause remains a mystery. In addition, the researchers also found that strange black spots with changeable contours and flickering appeared on the ultraviolet image of Venus. These black spots appear on the ultraviolet image because there is no ultraviolet light reflected from those places, as if something or someone absorbed the ultraviolet light!

Who absorbed these ultraviolet rays? What is hidden at an altitude of 80,000 meters? One theory is that they are hidden in the clouds in the form of life, absorbing ultraviolet rays from the sun as energy. Why not? Just as plants on the earth use visible light for photosynthesis, these creatures hidden in the clouds of Venus make organic matter by absorbing ultraviolet light.

There are creatures hidden in the clouds? This is not nonsense. As we all know, in the upper atmosphere of Venus at an altitude of 80,000 meters, the climatic conditions are much more suitable than the surface of Venus (the temperature here is 10 20. While the surface temperature of Venus is around 460), the air pressure can bear it, and there is even some water! Suspended water droplets provide an excellent shelter for some microorganisms. Think about the earth where we live. Isn't there bacteria in the cloud?

Unfortunately, there is no evidence to confirm this conjecture. However, it is gratifying that various detectors will continue to work hard on Venus. At present. Both the European Space Agency and the National Aeronautics and Space Administration of the United States are preparing for the Venus exploration mission in the next few years. In May of 20 10, Japan launched the first Venus probe "Dawn", but the probe failed to enter the scheduled orbit suitable for observing Venus' meteorology and encountered a failure.

Is there life on Pluto?

Pluto can also give birth to life? It's incredible! This dwarf planet is very far away from the sun (4.473 billion kilometers). It is extremely cold and barren (the average surface temperature is only 230℃), so far no detector has visited it. It is not difficult to imagine the situation on Pluto: a frozen world composed of nitrogen, carbon monoxide, methane and hard ice. However, scientists at Norton College in the United States believe that there will be life in the Kuiper Belt (the boundary of the solar system as we now know it)!

Indeed, there is almost no life on Pluto today, but what about the past? Jeffrey Collins believes that Pluto may have experienced a relatively good time when he was young, so that life appeared in its underground ocean!

Don't understand? Well, for the sake of understanding, let's start with Pluto, the largest moon of Pluto. According to the model established by the researchers, in the early solar system, Pluto may have collided with a giant celestial body, and the debris generated by the collision ran around Pluto and gradually aggregated into Pluto. That violent impact may have caused the temperature of Pluto to climb by 50%, which, although it could not break the hard ice, at least opened the prelude to a series of other thermal phenomena.

Researchers believe that Pluto therefore has a water-filled past. After that impact, Ka Rong stayed next to Pluto and spun around it quickly. Compared with other satellites, Phobos is really amazing in size, and its mass is about 1/7 of Pluto (the mass of the moon is 1/8 1 of the earth). You might say that Ka Rong has a strong gravitational force on Pluto, and Ka Rong was close to Pluto at that time, so the gravitational force was stronger. Under the action of gravity, Pluto is elongated into an ellipsoid. This stretching may lead to mutual friction between rocks, thus raising the temperature of the core and melting part of the ice covering Pluto's rock core, forming an underground ocean.

Perhaps it is in this underground ocean that life can flourish. However, researchers can't further demonstrate this point, after all, their information is extremely limited. How deep is this underground ocean? Is it located in rocks or ice (Pluto's core is made of rocks and covered with ice)? How long has it existed (a long time ago, the underground sea froze again. Because Phobos is gradually moving away from Pluto, its influence on Pluto is correspondingly weakened? Let's expect 20 15 when. The US "New Horizon" probe will arrive in Pluto and send back the photos of the mysterious ice dwarf for the first time. I hope it can bring us more stories about Pluto's past.

Why is Uranus on his back?

Uranus rotates in a very strange way, just like a child lying on the orbital plane. The rotation axes of other planets in the solar system are almost perpendicular to the orbital plane of the solar system, but the rotation axis of Uranus can be said to be located on the orbital plane, with an inclination as high as 98, and almost horizontally orbits the sun.

For a long time, researchers believe that this is due to the fact that Uranus was hit by a huge celestial body shortly after its formation, which led to the rapid turnover of its rotation axis. The idea was tempting, but it met with great difficulties. Since all the satellites of Uranus rotate on their equatorial plane (tilted due to the tilt of Uranus' axis of rotation), their orbits are also tilted. However, if the fact is as the researchers hypothesized-Uranus flipped quickly after being hit, how can its satellite adapt to this movement in a short time?

At the beginning of 20 10, Jacques laskar and gwinner El Bouai of the Paris Observatory tried to answer this question. Two astrophysicists believe that Uranus' turnover process may be very slow, so its satellites have enough time to follow up. This explanation seems more logical, however, there is still a question to be answered: who is the perpetrator of the impact? Was it an early companion of Uranus? In this regard, scientists can only give a rough description: the gravity generated by a giant plow satellite, coupled with the gravity of the sun, gradually overthrew Uranus' axis of rotation.

After calculation, the researchers believe that a satellite about 1.3 thousand kilometers away from Uranus may be the initiator of this impact. However, none of Uranus' known satellites meets these conditions!

So, is this mystery still unsolved? Not necessarily. Perhaps it is because Uranus' influential companion star was ejected to a far place under the gravity of another gas giant planet (Jupiter, Saturn ...), so that we haven't found it yet. Some simulation experiments have confirmed that the orbits of these gas giants may have moved a lot during the long formation of the solar system. As for the follow-up research progress, let us wait and see.

Is mercury big?

Come on! This barren land full of craters also contains secrets? Mercury has no atmosphere, no water, and suffers from strong radiation from the sun, which seems to make researchers uninterested. As we all know, there is a puzzling secret hidden in the depths of this planet, which is somewhat similar to the moon: the iron core. In fact, it is not unusual to have an iron core. After all, planets like Venus and Earth all have similar metal cores. These planets were all formed of the same substance at the same time, so their compositions should be similar. Iron is the heaviest of the main components that make up the earth. Therefore, when a celestial body is formed, it will sink to the deepest part of the celestial body. As the core of the earth, its diameter is about 1/2 of that of radius of the earth. In contrast, the radius of Mercury is 2400 kilometers, while the radius of its iron core reaches 1900 kilometers. In other words, this mysterious iron core almost occupies the whole mercury! It is rare that mercury's heart is so huge!

There are two opposite theories to explain this. The first theory holds that this phenomenon is caused by the infinite power of the sun. Mercury is very close to the sun, only 60 million kilometers (the earth is 65.438+0.5 billion kilometers away from the sun), so it is strongly radiated by the sun, and the temperature can reach 460! At the beginning of the formation of the solar system 4.5 billion years ago, the situation seemed even worse: at that time, the sun was very violent and released much more energy into space than it does now, making the early mercury temperature as high as 2000! Huge heat evaporated the rocks in the outer layer of Mercury, leaving only a planetary mantle 500 kilometers thick.

Another theory-"Cosmic Billiards Theory"-is even more amazing. A group of researchers at the University of Berne in Switzerland believe that the early Mercury (about 4.5 billion years ago) may have suffered one or even many catastrophic violent impacts. At that time, everything in the solar system was chaotic, and collisions between celestial bodies were very frequent (the moon was also formed in such collisions). Therefore, the researcher's theory is not nonsense. In order to prove their point of view, they used computers to simulate various collisions, constantly changing the parameters such as the mass and impact speed of colliding celestial bodies. When they assumed that a celestial body about the size of the moon hit Mercury at a speed of 654.38+100000 km/h (twice the mass now), they finally got the status quo of Mercury-the thin mantle and crust were wrapped in a huge and complete core, and those evaporated surface materials might become part of the sun and other newborn planets. The results show that there may even be 1.6 10 16 tons of debris integrated into the earth! At that time, the earth was just a hot sphere, and the fragments of mercury merged with it, and now it is beyond recognition.

However, the mystery of Mercury's iron core may soon be solved. 20 1 1 In March, 2008, the United States explored the orbit around Mercury, and one of its tasks was to find out the truth by analyzing the composition of the surface of Mercury. After all, if the surface substance of mercury really evaporated, its surface should now be free of volatile components (such as sodium and potassium).

6. Titan, the only satellite with an atmosphere.

The orange sky is densely covered with stratus clouds, rivers of liquid ethane meander across the vast plains, and lakes full of hydrocarbons ripple under the action of wind and lightning.

Welcome to Titan! With a diameter of 5 150km, it is Saturn's largest satellite, even larger than Mercury. In addition, it is the only satellite in the solar system 166 with an atmosphere. It is surrounded by a cold atmosphere with an average temperature of only -200 * (Celsius), which is denser than the earth's atmosphere. Its main components are nitrogen (about 95%) and methane (about 5%).

Why is Titan's surface covered with such strange fog? Is it because it is huge? That's true. The reason why the atmosphere did not escape was because it was bound by Titan's gravity. The greater the mass of the celestial body, the greater the gravity, and the easier it is to retain gas. Most satellites in the solar system can only let the atmosphere escape because of their small mass, but Titan is a very strong "strong man". So, everything seems reasonable. However, Titan is not the only "big" celestial body, and other satellites have similar "celestial bodies". For example, Ganymede (5,260 kilometers in diameter) is even bigger than Titan, and Ganymede (about 4,820 kilometers in diameter) is almost the same size as Titan. Strangely, Ganymede and Callisto are naked. ...

Astronomers who have always been imaginative naturally have some views on the mystery of Titan's atmospheric formation. They think Titan's atmosphere may be as old as Titan itself. Titan is formed by accretion. Specifically, dust particles, pebbles and rocks collide with each other and fuse together to form Titan. Due to the heat released during the accretion process, ammonia and methane originally existing in rocks in the form of ice are ejected and then retained by Titan's gravity. With the passage of time, ammonia molecules are transformed into liquid nitrogen and hydrogen under the action of solar high-energy particles, and most of the latter escape. In this more than 10 million years, the original methane also reacted chemically under the action of sunlight until it disappeared. At present, there is still 5% methane in the atmosphere, because this gas has been ejected from the depths of Titan.

Well, there's only one question left: Why don't Ganymede and Callisto have an atmosphere? This is still a mystery. However, this seemingly confusing puzzle is actually traceable. According to scientists' speculation, compared with Titan, the formation process of these two satellites is relatively slow, the accretion process may be much milder, and the heat released is relatively small, which is not enough to heat the volatile components such as ammonia and methane in the form of ice inside the celestial body. Since there is no gas, how can there be atmosphere?

However, the research is not over. If we want to further solve the mystery, we must carefully study the composition of Ganymede and Callisto, which is the goal of the Europa-Jupiter system jointly organized by the European Space Agency and NASA. However, this beautiful vision may be difficult to achieve before 2025.

7. Saturn's rings are getting brighter?

The delicate and shiny white halo seems to put a beautiful belt on Saturn. They are the bright "stars" in Saturn's rings and the solar system. However, like all high-profile stars, age is a secret that cannot be told. Can you believe that they seem to have existed for less than a few hundred million years, but in fact they were born for 4 billion years.

In order to find out the age of Saturn's rings, astrophysicists carefully observed their shapes and found that they were made up of countless ice cubes colliding with each other. In this way, the question arises: If Saturn's rings have existed in the universe for about 4 billion years, why is its torus still bright instead of being dark and dark by dust? In addition, there is another problem: it stands to reason that these constantly colliding ice cubes should cut the torus very thin. Why is there a huge rock with a diameter of about 10 meter in Saturn's rings besides dust? In this view, this round of Saturn's rings should be in the prime of life! But why do astrophysicists go back to the early solar system?

This is because astrophysicists can almost conclude that Saturn's rings were formed by the disintegration of a celestial body with a diameter of about 400 kilometers. This celestial body may be a satellite of Saturn. Because its orbit is too close to Saturn, it is torn by Saturn's gravity, and the debris produced is distributed around Saturn, forming a beautiful light ring. But the problem is that withered celestial bodies wandering around the solar system only exist in the early solar system where planets have just formed. In addition, as mentioned above, celestial bodies collided quite frequently at that time, and early Mercury, Mars and Earth were all hit by huge projectiles. Unlike them, Saturn had disintegrated a huge projectile before it was hit, which could only happen in the early solar system about 4 billion years ago. Who would have thought that Saturn's rings with bright appearance were so old?

The Cassini probe, which has been flying around Saturn for five years, has collected a lot of data and unveiled the corner of its veil for the world. The probe found that young satellites were forming in Saturn's rings. Small particles pile up to form large particles, and the large particles further pile up into larger lumps-this is the accretion phenomenon mentioned above. Many planets and their satellites are accretion.

In the early solar system, the cosmic dust floating in the air mass combined into stones, and then these stones collided countless times and eventually accumulated into celestial bodies with a diameter of several thousand meters. However, the nightmare also began! Saturn's terrible gravity began to act cruelly on this newborn celestial body, causing it to suffer the fate of the previously torn celestial body: falling apart and returning to dust. Debris is ejected from the inside of the newborn satellite. Because the outside is covered with dust, these debris remain spotless and clean as new. That is to say, in the process of circulating in the ring, substances dilute and absorb pollutants in the universe. It's like when you break a snowman that has been piled up, you will find that the broken snow is particularly white at this time. Saturn's rings are constantly renewing themselves, leaving the world with the illusion of eternal youth.

8. Is there Wang Yang Sea on Europa?

What? That striped and ugly little ice hockey is the perfect hiding place for life? Yes, this hidden guy is Europa, and his strength cannot be underestimated. Europa has three necessary conditions for life: heat, organic molecules and liquid water.

Yes, liquid water, it's true! Scientists are convinced that there is a vast ocean under Europa's thick ice layer, as evidenced by the criss-crossing and cobweb-dense stripes on its surface. These stripes are ice cracks, that is, the connection points of major ice blocks. On earth, the crust is not a whole, but consists of several plates floating on hot magma. On Europa, ice replaced rocky land and magma was replaced by underground ocean.

If there must be Wang Yang sea under the ice, is there any organic molecule as the basis of life in this sea? In this regard, researchers are also quite confident. At present, we know that the original organic matter on the earth came from meteorites that hit the earth in the early solar system, and Europa has no reason to escape the attack of meteorite shower.

What makes the researchers hope is that Europa's environment is quite similar to Oriental Lake (located under the ice layer of more than 3,000 meters near the Oriental Station in Antarctica, it is the deepest and largest glacial lake in the world, with an area of about 150 times that of Paris, France). If life can be found in Lake Vostok, it may prove that there is life in the ocean under Europa's ice. In fact, scientists have found bacteria in the ice core samples of the lake! Yes, even in such an extremely harsh natural environment (there is no sunshine all the year round, the thick ice layer causes great pressure, and the heat of the center of the earth makes the temperature at the bottom of the lake as high as 350 degrees), life can still be nurtured. In this case, does it mean that there is life on Europa? The problem is that it may be relatively easy to survey glacial lakes, but it is much more difficult to detect Europa, which is nearly 800 million kilometers away from the earth! First of all, we have to go through an extremely difficult journey. Even if you reach Europa successfully, you should drill a hole in the unfathomable ice (scientists have different opinions and think it is 2 km 100 km)! It seems that if you want to uncover the hidden secret of MuWei son, I'm afraid you have to wait patiently for decades.

9. Does the sun have an invisible "elder brother"?

What? Is there a "brother" in the sun? Why can't we see it? There is obviously only one sun shining in the sky! That's true. If the sun has a "brother", it may exist outside the solar system, at least 1 light-year away from the earth, and it is very dim, so it has never been detected by space telescopes. This sun companion was named "Nemesis" (Nemesis in Greek mythology) by astronomers. Under the action of gravity, the sun and Nemesis revolve around the same center of mass.

By the way, why do researchers assume the existence of this unknown star? Because it may be the chief culprit that caused the solar system (including the earth) to be bombarded by periodic meteorites, the extinction of dinosaurs 65 million years ago may be caused by an asteroid hitting the earth, and the projectile may come from Oort Cloud. Specifically, when Nemesis passed near Oort Cloud, it disturbed Oort Cloud in some way due to gravity, thus throwing some long-period comets out of Oort Cloud and causing comet rain.

Another important clue to prove that the sun has a companion star is that there is a mysterious dwarf planet called Sedna outside Pluto's orbit. However, the strange orbit of this dwarf planet is really puzzling: it follows a rare orbit with a very large eccentricity, and its perihelion and apohelion are about 76 astronomical units and 975 astronomical units respectively. Sedna's existence indirectly proves that the sun still has a companion star: if it is in a dilemma between the sun and Nemesis, then this amazing eccentricity can be easily explained.

In view of this evidence, the researchers assume that the sun is not alone, but has a companion star like 1/3 stars in the Milky Way. The remaining work of scientists is to find out the hidden sun "brothers". However, astronomers have been struggling for this for more than 20 years, but it has always been fruitless. Now, scientists hope that the "Wide-area Infrared Skywalker" observation satellite launched at the end of 2009 can find its trace. A round-up drama began.

10. Does Mars have a "yin and yang face"?

Although Mars has always been full of visitors, this red planet still contains unsolved mysteries. What a tough guy! It seems that the more we explore, the more obsessed it is with the game of hide and seek. But ... what bothers researchers more is its strange "yin and yang face": the northern hemisphere is low and flat, although there are several volcanoes on the flat plain, it is as dry as the seabed; The southern hemisphere is towering into the sky, mainly in highlands, and craters of all sizes are scattered all over the place (just like the landform of the moon).

Why are the topographical styles of the northern and southern hemispheres of Mars so different? For a long time, researchers have been puzzled by the northern hemisphere. After all, it is perfectly reasonable for celestial bodies to be covered with craters. In the early solar system, meteorites bombarded all the planets, leaving a large number of craters. The earth has not been spared, but the traces left by meteorites on the earth have been smoothed by natural factors such as erosion and plate movement. Due to the plate movement inside the earth, the surface of the earth has undergone earth-shaking changes. On the contrary, due to the lack of atmosphere and plate movement, mercury and the moon have almost no complete craters.

What about Mars? Even if this red planet has experienced an internal activity in the past, it will not make the surface so flat, not to mention why only the northern hemisphere presents this landform, but the southern hemisphere is completely different?

For this puzzle, the European probe "Mars Express", which has been flying around Mars since 2003, has given some answers. With the help of radar analysis, the detector found that the crust hidden under the smooth surface of the northern hemisphere is as full of craters as the southern hemisphere! It's just that the crust in the northern hemisphere is covered with a layer of lava and sediment (sand-ice mixture) with a thickness of three or four kilometers, which covers up the truth of the potholes.

So, in that case, why is this sedimentary phenomenon unique in the northern hemisphere where volcanoes are distributed? This is precisely because of the topographical characteristics of Mars. The reason why there are so many lava and sediments piled up together. It is precisely because the topography of the northern hemisphere is like a huge basin, which is completely different from that of the southern hemisphere.

Next, scientists will trace back to the cause of the formation of this basin. Guess which theory prevailed?

It still has an impact! Yes, according to this theory, when Mars was young, its northern hemisphere may have been strongly bombarded by a giant celestial body, thus forming a huge basin and evaporating part of the crust. This theory not only explains the origin of the basin, but also explains why the average thickness of the crust below the basin is only 40 kilometers, while the thickness of the crust in other places reaches 70 kilometers. As for the southern hemisphere, it narrowly escaped the impact and was almost intact.

At present, among all kinds of theories, the theory of impact is smooth sailing. Nevertheless, further proof is needed. If there is indeed a huge satellite around Mars, then this theory will be perfectly confirmed. Because a large number of debris thrown during the impact may have gathered into a satellite. After all, the moon, the satellite of the earth, was formed in this way. Coincidentally, some simulation experiments have confirmed that Phobos (the largest satellite of Mars) was produced by this impact. However, Phobos has a maximum diameter of only 27 kilometers. Compared with the size of the basin and the number of fragments bouncing back into space from the earth's crust during impact, Phobos's "size" is really pitiful. The moon is about 3400 kilometers in diameter. What about Phobos, the son of Mars? We are still waiting for the answer.

Undoubtedly, the ballet performed by various detectors on this red planet is far from the curtain call!