700 million years - it took so much for our solar system to form. A short time on the scale of the Universe. But all the key events for our "solar family" managed to happen during this time. What are they?
In the beginning there was a cloud
It all started about 4 billion 600 million years ago. It was then that a huge cloud of molecular dust, quietly floating in the Milky Way, suddenly began to shrink. This happened thanks to a supernova that flared up nearby, the shock wave from which passed through the entire cloud and provoked a gravitational collapse. And the explosion of a giant star filled the cloud with gas and heavy elements - iron and uranium, which later became the bricks that make up the solar system.
The compression was very fast. In addition, the cloud also rotated. The fact is that everything around us, including the galaxy, is in constant rotation. Rotation is part of the physics of stellar collapse. When gravity arose in the gas-dust cloud, it not only began to rotate faster, but also flattened into a disk. Under conditions of rapid compression and chaotic rotation, gas and dust began to compact into many lumps. These lumps were nothing more than future stars.
Very soon, part of this cloud will become a fragmented solar system, in the center of which a bright protostar will shine. It will begin to absorb dust and gas, which then consisted of the solar nebula. Most of all this "garbage" will be in the depths of the Sun, and planets, satellites, asteroids and even ourselves are formed from the scanty remnants.
The solar system was not the only "child" of a huge gas and dust cloud, at the same time its "brothers" - other stellar systems - are "born" with it.
We can observe the same thing today in the constellation Orion, through which a giant molecular cloud stretches hundreds of light years. In some places, young stars can be seen from these clumps, like giant disco balls, illuminating the surrounding gas with all the colors of the rainbow.
Promotional video:
Orion nebula
Photo: NASA
Today there are two approaches to the formation of planetary systems. One of them is the development of the ideas of the Soviet scientist Viktor Safronov, the so-called model of accretion onto the nucleus. According to this model, at first a certain blank of the planet is formed, an embryo, a rocky core, onto which gas then accrets, and a giant planet like Jupiter, Saturn or other giant planets is formed. The second approach is associated with attempts to explain the formation of planets in the protoplanetary disk by the same mechanism that leads to the formation of stars, that is, gravitational instability. If the disk is massive enough, and there is a lot of matter in it, then some inhomogeneities can form, which will be compressed under the influence of their own gravity. If they are massive enough, they will fall inward,collapse and turn into massive planets. In the scientific community, the first, the Safronov theory of the formation of planets, still has an advantage.
Planethesimals
In its "infancy", the solar system did not have any planets. The Sun itself did not exist as such either - there was only a small protostar, the light from which was very dim due to the gas and dust accumulated around it. However, the planets will form very quickly.
The material for their "making" was divided into several "layers" depending on the temperatures of the disk. Closer to the protosun, at temperatures over 2,000 degrees, everything evaporated. At a distance of 8 million km, there was a stone line where metals and minerals were solidified. The next boundary is usually called the snow line - this is the upper boundary of the inner solar system. Water, methane and ammonia exist here only in the form of ice. But why are we talking about these substances? It's simple - there are most of them in the solar system, especially water. These are all components of hydrogen in one form or another, and hydrogen is the most abundant element in the solar system at that time.
Both these and other elements are united by one thing - they are still here in the form of microscopic particles. But very soon, by accretion, they will begin to be attracted to each other, and they will turn into stones and pieces of ice, which, in turn, will also attract together. They form more or less large stone pieces (about 1 km by 1.5 km), called planetesimals. This is the first building material from which protoplanets, the "embryos" of planets, will be formed in 3 million years.
Artistic vision of the snow line
Photo: ESA
Gas giants
In the meantime, protoplanets are similar in size to the Moon. Colliding with each other, they form large planets. The planets of the inner solar system - Mercury, Venus, Earth and Mars - turned out to be small, smaller than the outer ones, because they got less building material (closer to the star, where it is hot enough due to its radiation, ice cannot condense, cannot condense water, ammonia and other gases into solid matter, therefore only rocky planets can be formed there, so these planets are less massive, because less matter is available for their formation).
Literally in 3 million years, a giant of the solar system appears - young frozen Jupiter. Before becoming a gas giant, Jupiter was a super-earth - a large rocky planet with a mass several times that of Earth. It continued to grow, attracting more and more protoplanets to itself. Because of its mass, Jupiter has become a "gravitational robber". Like a space vacuum cleaner, it absorbed all gases in its path and in 100 thousand years has increased 90% of its current mass.
Other planets in the outer solar system - Saturn, Uranus and Neptune - followed his "hooligan" example. And although most of them failed to accumulate such a convincing "muscle" mass, Jupiter and Saturn ultimately absorbed 92% of all non-solar matter!
Thanks to the "gluttony" of these two giants over the 10 million years of the existence of the young solar system, almost all the gas in it, in particular, hydrogen and helium, due to which Jupiter and Saturn grew so quickly, ran out. Their irrepressible "greed", however, played into the hands of their more "modest" brothers. After all, if Jupiter and Saturn did not attract all the gas and dust, we could contemplate our Sun only as a rather dim fuzzy disk. However, they could not - in the absence of normal sunlight, life on our planet could hardly achieve such a variety that such curious creatures as Homo sapiens appeared on it. The sun, however, contributed to this itself. After all, it continued to absorb hydrogen and helium, otherwise it would not have grown to this size, and remained a protostar. Jupiter, by the way, could have become a star himself,if it had a much greater mass.
The second birth of the Sun
Our Sun was born twice. The star we have talked about so far was only a protosun. At the beginning of her life, the spectrum of her light was different. The protosun was as energetic as it is now, but more red. At the age of 50 million years, a significant event occurs with the solar system - our star reaches a critical temperature and pressure, and a nuclear reaction begins in its core. With the energy of a hydrogen bomb, our protosun explodes, and a new full-fledged star is born.
Inner planets
The sun was ripe, and the formed Jupiter, Saturn, Uranus and Neptune flew over the snow line. Meanwhile, in the hot inner region, where there were many rocks and little gas, chaos ensued as tiny protoplanets continued to collide and grow.
The formation of the inner planets of the solar system lasted 10 times longer than the formation of gas giants. After 75 million years, this process has come to an end. The dust of these "battles" scattered, and outlines of the four inner planets - Mercury, Venus, Earth and Mars - emerged from the depths of space.
The childhood of our Earth, however, was difficult. At the time when proto-earth reached its current size and took up a stable orbit, it had a space pursuer. It is believed that in the initial stages of development, the Earth was accompanied by another protoplanet - Thea. It had almost the same orbit as Earth. She literally followed her heels. It is not surprising that such "control" sooner or later had to result in a fierce "conflict" - the planets collided. And again, great disasters turned into a great creation - from the fragments of Thea and the Earth itself, a satellite - the Moon was formed (read about this in the last issue of the magazine in the article "History of the Earth in 30 minutes"). Having survived the cataclysm and formed the Moon, the Earth has become one of the most stable planets in the inner solar system. This is probably another reasonwhy life appeared on it (at least, so diverse).
Asteroid Ring and Kuiper Belt
It would seem that the formation of the planets is over, but between Mars and Jupiter to this day there is a ring that should have turned into another planet a long time ago. But her birth is impossible - the "villainess-fate" in the form of the giant Jupiter does not allow her to form: the gravitational force of the gas planet constantly pushes asteroids together and prevents them from being attracted to each other.
Closer to the edge of the solar system, beyond the orbit of Neptune, is another ring of asteroids - the Kuiper belt. It contains a lot of rocks and ice, but they all fly so far from each other that they almost never collide, therefore they do not form planets.
The objects of the main belt are shown in green, the scattered disk - in orange. The four outer planets are highlighted in blue, the Trojan asteroids of Neptune in yellow, and Jupiter in pink. The appearance of the gap at the bottom of the figure is due to the presence of the Milky Way strip in this area, hiding faint objects
In addition to the asteroid ring and the Kuiper belt, there is also a hypothetical spherical region in the solar system called the Oort cloud. It is she who, according to many researchers, is considered the "homeland" of long-period comets. And although the existence of the Oort cloud is not instrumentally confirmed, many indirect data indicate its existence. The Oort cloud is believed to be the remnant of the original protoplanetary disk that formed around the Sun about 4.6 billion years ago. The generally accepted hypothesis is that Oort Cloud objects originally formed much closer to the Sun in the same process that planets and asteroids were formed, but gravitational interaction with young giant planets such as Jupiter threw these objects into extremely elongated elliptical or parabolic orbits. …
Late heavy bombardment
However, 50 million years after the birth of the solar system, there were 100 times more bodies in the Kuiper belt and asteroid ring than today. All of them played a destructive but very important role in the evolution of the rocky inner planets, including our Earth.
The cause of the drama, however, was then the gas giants, whose displaced orbits nearly destroyed the solar system. When Jupiter entered into resonance with Saturn, gravitational excitement arose and a catastrophe occurred - the planets scattered across the solar system. Two planets, Neptune and Uranus, suffered the most. Their orbits are reversed.
The Jupiter-Saturn resonance has thoroughly thinned out both the asteroid belt and the Kuiper belt. 99% of the bodies in the asteroid and Kuiper belts scattered, most of them were outside the solar system. But some went inside. The earth, like other rocky planets, was in the line of fire. This event is known as the late heavy bombardment. But the “no silver lining” principle worked again. Many scientists believe that it was precisely such bombings that could bring water to Earth, and at the same time organic minerals and substances from which life later developed.
Since then, as far as modern science knows, there have been no serious cataclysms in the solar system. Many generally consider it atypical in comparison with other similar systems precisely because of its stability. Are we special?..
The solar system should exist for another 5 billion years - until the thermonuclear reaction in the interior of the sun stops and it expands. When this happens, it will turn into a red giant and swallow Mercury, Venus, and possibly our Earth. But even if our planet avoids this fate, life on it will become completely impossible due to the proximity of the giant sun. The habitable zone will shift to the very edges of the planetary system. However, due to the extremely increased surface area, the Sun will be a much cooler star than before. After that, our system will face an even greater tragedy - the Sun will begin to shrink again. This will continue until it turns into a white dwarf - a stellar core, an unusually dense object half the original mass of the star, but only the size of the Earth. The process of "dying" of the Sun, like everything else in this world, began at the time of its birth. As the sun burns up its reserves of hydrogen fuel, the energy released to support the core tends to run out, causing the star to contract. This increases the pressure in its interior and heats up the core, thus accelerating the combustion of fuel. As a result, the Sun brightens about ten percent every 1.1 billion years, and will brighten another 40% over the next 3.5 billion years. As a result, the Sun brightens about ten percent every 1.1 billion years, and will brighten another 40% over the next 3.5 billion years. As a result, the Sun brightens about ten percent every 1.1 billion years, and will brighten another 40% over the next 3.5 billion years.