700 million years – were required so much in order that our Solar system was created. Insignificant term in Universe scales. But all key events for ours “solar family” have managed to take place during this time. What?
At the beginning there was a cloud
Everything has begun about 4 billion 600 million years ago. Then the huge cloud of molecular dust which was quietly floating in the Milky Way suddenly began to contract. It happened thanks to the supernew star which has flashed nearby from which shock wave has passed through all cloud and has provoked a gravitational collapse. And explosion of a huge star has filled a cloud with gas and heavy elements – iron and uranium, after become bricks of which the Solar system consists.
Compression happened very quickly. In addition, the cloud also rotated. The matter is that all around us, including a galaxy, is in continuous rotation. Rotation is a part of physics of a star collapse. When in a gas-and-dust cloud there was a gravitation, it not only began to rotate quicker, but also was flattened out in a disk. In the conditions of rapid compression and chaotic rotation gas and dust have begun to be condensed in a set of lumps. These lumps were nothing else as future stars.
Part of this cloud will become soon the shattered Solar rule in which center the bright protostar will begin to shine. She will begin to absorb dust and gas of which then the solar fog consisted. The most part from all this “garbage” will appear in a subsoil of the Sun, and planets, satellites, asteroids and even ourselves are formed of the scanty remains.
The solar system was not only “child” of a huge gas-and-dust cloud, along with it on light also her “brothers” – other star systems “are born”.
We can observe the same today in the constellation of Orion through which the huge molecular cloud hundreds light years long was stretched. In some places it is visible how young stars as if the huge disco spheres highlighting the gas surrounding them all colors of the rainbow are formed of these lumps.
Fog Oriona / ©NASA
Today there are two approaches to a question to formation of planetary systems. One of them is a development of the ideas of the Soviet scientist Victor Safronov, so-called model of accretion on a kernel. According to this model, at first a certain procurement of the planet, a germ, a stone kernel on which then akkretsirut gas is formed, and the giant planet like Jupiter, Saturn or other giant planets is formed already. The second approach is connected with attempts to explain formation of planets in a protoplanetary disk with the same mechanism which leads also to formation of stars, that is gravitational instability. If the disk is enough массивен, and in it there is a lot of substance, then some heterogeneities which will contract under the influence of own weight can be formed. If they are enough massivna, they will fall in themselves, to collapse and turn into massive planets. In the scientific environment the first has an advantage so far – the safronovsky theory of formation of planets.
In “infancy” the Solar system had no planets. The Sun as such didn’t exist too – there was only a small protostar from which light was very dim because of the gas and dust saved around it. However, planets will be created very quickly.
Material for their “production” was divided into several “layers” depending on disk temperatures. Closer to protosolnets, at a temperature over 2 thousand degrees, everything evaporated. At distance of 8 million km there was a stone line where metals and minerals hardened. It is accepted to call the following boundary the line of snow – this upper bound of an internal Solar system. Water, methane and ammonia exist only in the form of ice here. But why we speak about these substances? Everything is simple – in their Solar system most of all, especially waters. They are hydrogen components in this or that type, and hydrogen is the most widespread element in the Solar system of that time.
As these, and other elements, one unites – they are here in a type of microscopic particles so far. But already soon by accretion will begin to attract them to each other, and they will turn into stones and pieces of ice which, in turn, too will attract together. More or less big stone pieces (about 1 km by 1,5 km), the called planetezimal are formed of them. It is the first construction material from which through 3 million years protoplanets – “germs” of planets will be created.
For now protoplanets are similar in the sizes to the Moon. Facing among themselves, they form major planets. Planets of an internal Solar system – Mercury, Venus, Earth and Mars – turned out small, it is less external because they got less construction material (closer to a star where it is rather hot because of its radiation, ices can’t be condensed, water, ammonia and other gases therefore there formation only of stone planets is possible can’t be condensed in solid substance. Therefore these planets turn out less massive, less substance is available to their education).
Literally for 3 million years there is a giant of the Solar system – the young frozen Jupiter. Before becoming the gas giant, Jupiter was superzemly – the large stone planet which mass several times exceeds the mass of Earth. It continued to grow, attracting to itself(himself) all new protoplanets. Because of the weight Jupiter became “the gravitational robber”. As the space vacuum cleaner it absorbed all gases on the way and for 100 thousand years increased 90% of the present masses.
Other planets of an outer Solar System – Saturn, Uranium and the Neptune – followed his “hooligan” example. And though most of them didn’t manage to save up so convincing “muscular” weight nevertheless, Jupiter and Saturn finally incorporated 92% of all not solar substance!
Thanks to “gluttony” of these two giants for 10 million years of existence of a young Solar system in it practically all gas, in particular, hydrogen and helium because of which Jupiter and Saturn so quickly grew came to an end. Their irrepressible “greed”, however, helped their more “modest” fellows. If Jupiter and Saturn didn’t attract all gas and dust, we could contemplate our Sun only as quite dim indistinct disk. However, couldn’t – in lack of a normal sunlight life on our planet could hardly reach such variety that on it so curious beings as Homo sapiens appeared. The sun, however, promoted it also. It continued to incorporate hydrogen and helium, otherwise wouldn’t grow to such sizes, and having remained a protostar. Floodlight, by the way, and itself could become a star if had considerably bigger weight.
Rebirth of the Sun
Our Sun was born twice. That star about which we spoke still was only protosolnets. At the beginning of the life her light spectrum was another. To Protosolntsa had huge energy as well as now, but was more red. At the age of 50 million years to Solar system there is a milestone event – our star reaches the critical temperature and pressure, in her kernel nuclear reaction begins. With energy of a hydrogen bomb ours protosolnets blows up, and the new full-fledged star is born.
The sun has ripened, and the created Jupiter, Saturn, Uranium and the Neptune have departed for the snow line. Meanwhile, in hot internal area where there were many stones and not enough gas, chaos was created: tiny protoplanets continued to face and grow.
Education of internal planets of Solar system was continued by 10 times longer, than formation of gas giants. Later 75 million years this process has come to an end. Dust of these “fights” has dissipated, and from depths of space outlines of four internal planets – Mercury, Venus, Earth and Mars have appeared.
The childhood of our Earth nevertheless was difficult. When протоземля has reached the present sizes and has occupied a stable orbit, it had a space persecutor. It is considered that at initial stages of development Earth was accompanied by other protoplanet – Teja. She had almost same orbit, as well as at Earth. She literally followed her close. It is no wonder that similar “control” had to develop into fierce “conflict” sooner or later – planets have faced. And again great disasters have turned back great creation – the satellite – the Moon was created from Teja’s fragments and Earth (read about it in the last issue of the magazine in the article “Earth History in 30 Minutes”). Having survived in a cataclysm and having created the Moon, Earth became one of the stablest planets of internal Solar system. Possibly, it is one more reason why on it life has appeared (at least, so various).
Ring of asteroids and Kuiper belt
It would seem, formation of planets is finished, but between Mars and Jupiter there is to this day a ring which very long time ago had to turn into one more planet. But her birth is impossible – “villain destiny” in an image of the giant of Jupiter doesn’t allow it to be created: the gravitational force of the gas planet constantly pushes together asteroids and doesn’t allow them to be attracted to each other.
Closer to edge of Solar system, behind the Neptune’s orbit, one more ring of asteroids – the Kuiper belt has settled down. In him there are a lot of stones and ice, but all of them fly so far apart that almost never face therefore don’t form planets.
Objects of the main belt are shown in green color, a scattered disk – orange. Four external planets are highlighted in blue color, the Trojan asteroids of the Neptune – yellow, Jupiter – pink. Emergence of an interval in the lower part of the drawing is connected with stay in this area of the strip of the Milky Way hiding dim objects / ©Wikimedia Commons
Besides a ring of asteroids and the Kuiper belt, in Solar system there is also a hypothetical spherical area called by an Oort cloud. It, according to many researchers, is considered “homeland” of long-period comets. And though instrumentally existence of an Oort cloud isn’t confirmed, many indirect data indicate its existence. It is considered that the Oort cloud is the rest of an initial protoplanetary disk which was created around the Sun about 4,6 billion years ago. The standard hypothesis says that objects of an Oort cloud were originally formed much closer to the Sun in the same process in which planets and asteroids, but gravitational interaction with young giant planets, such as Jupiter were formed, rejected these objects into extremely extended elliptic or parabolic orbits.
Late heavy bombing
However, through 50 million years after the birth of Solar system in the Kuiper belt and a ring of asteroids was in 100 times more of bodies, than today. All of them played destructive, but very important role evolutions of stony internal planets, including our Earth.
Then gas giants whose displaced orbits nearly ruined Solar system became the drama reason, however. When Jupiter was included into a resonance with Saturn, there was a gravitational excitement and there was an accident – planets scattered on Solar system. Two planets – the Neptune and Uranium, were damaged most. Their orbits traded places.
The resonance Jupiter-Saturn thoroughly thinned out both a belt of asteroids, and the Kuiper belt. 99% of bodies in belts of asteroids and Koypera scattered, the most part from them appeared outside Solar system. But some went inside. The earth, as well as other stony planets, appeared in the firing line. This event is known as late heavy bombing. But the principle “there’s no evil without good” worked again. Many scientists consider that such bombings could bring water to Earth, and at the same time and organic minerals and substances from which life developed later.
Since then, as far as we know to modern science, serious cataclysms in Solar system didn’t take place. Many in general consider it atypical in comparison with other similar systems owing to its stability. Really we – special?.
The solar system shall exist about 5 billion more years – until thermonuclear reaction in a subsoil of the Sun doesn’t stop and it doesn’t extend. When it occurs, it will turn into the red giant and will absorb Mercury, Venus and, perhaps, our Earth. But even if our planet will also avoid this fate, life on it will become absolutely impossible because of proximity of the huge Sun. The zone of a habitability will be displaced to the edges of planetary system. However, because of extremely increased surface area the Sun will be much more “cool” star, than before. After that our system is waited still by the big tragedy – the Sun will begin to contract again. It will occur until it doesn’t turn into the white dwarf – a star kernel, extraordinary dense object in a half of initial mass of a star, but the size only about Earth. Process of “dying” of the Sun, as well as all in this world, began at the time of its birth. As the Sun burns inventories of hydrogen fuel, the marked-out energy supporting a kernel tends to come to an end, forcing a star to contract. It increases pressure in its subsoil and heats a kernel, thus accelerating combustion of fuel. As a result the Sun becomes about ten percent brighter each 1,1 billion years, and will become 40% brighter during the following 3,5 billion years.