The origin of the Milky Way

It was long thought that the Milky Way was formed gradually. In 1962, Olin Eggen, Donald Lynden-Bell and Allan Sendedzh offered a hypothesis that has become known as a model of ELS (it was called by the initial letters of their names). According to her, on the site of the Milky Way once slowly rotated homogeneous cloud of gas. It looked like a ball and reached across about 300 thousand light years, and consisted mainly of hydrogen and helium. Under the influence of gravity protogalaxy shrank and became flat; while its rotation is considerably accelerated.

For almost two decades, this model is suited scientists. However, new observations showed that the Milky Way could be as he ordered theorists.

According to this model, the halo formed first, and then - the galactic disk. However, the disc is also found very old stars, for example, a red giant Arcturus, whose age is more than ten billion years old, or multiple white dwarfs of the same age.

And in the galactic disk and the halo globular clusters are found who are younger than the model allows ELS. Obviously, they are absorbed within our Galaxy.

Many stars in the halo spin in a different direction than the Milky Way. Perhaps they, too, were once outside the Galaxy, but then were drawn into this "star vortex" - like the occasional swimmer in the whirlpool.

In 1978, Leonard Searle and Robert Zinn proposed their model of formation of the Milky Way. It was designated as a "model SZ». Now the story of the Galaxy considerably complicated. More recently, its youth, in the view of astronomers, described as simple, as in the opinion of physicists - straight forward movement. The mechanics of what is happening is clearly visible: there was a uniform cloud; it consisted of only evenly spilled gas. Nothing his presence does not complicate the calculations of the theoreticians.

Now, instead of one huge cloud in the visions of scientists arose several small, oddly scattered clouds. Among them could be seen and the stars; however, they are located only in the halo. Inside, all seething Halo: clouds encountered; gas mixture is stirred and compacted. Over time, the mixture was formed galactic disk. It began to appear new stars. However, this model was criticized afterwards.

It was impossible to understand what tied the halo and the galactic disk. This thickens the drive and a sparse stellar shell around it had little in common. Even after Searle and Zinn made his model, it was found that the halo is rotating too slowly to from it formed the galactic disk. Judging by the distribution of chemical elements, the latter originated from protogalactic gas. Finally, the angular momentum of the disc turned ten times higher than halo.

The whole secret is that both models contain a grain of truth. The trouble is that they are too simple and one-sided. Both of them seem to be now the fragments of the same recipe, which was created by the Milky Way. Eggen and his colleagues read a few lines from one of this recipe, Searle and Zinn - a few others. Therefore, trying to re-present the history of our galaxy, and then we notice familiar already read one line.

So, it all started shortly after the Big Bang. "Today made to believe that the dark matter density fluctuations gave rise to the first structure - the so-called dark halo. Due to the force of gravity, these structures do not disintegrate, "- said the German astronomer Andreas Burkert, the author of the birth of a new model of the Galaxy.

The dark halo nuclei steel - nuclei - the future galaxies. Around them flocked by gravity gas. To uniformly collapse, he describes him as a model of ELS. Already 500-1000 million years after the Big Bang gas accumulation surrounding dark halo, they have become "incubators" of stars. There appeared little protogalaxy, in dense clouds of gas were first globular clusters, because the stars are born here a hundred times more often than anywhere else proto- galaxies collide and merge with each other - so formed large galaxies, including our own Milky Way. Today it is surrounded by a halo of dark matter and consisting of single stars and globular clusters, these ruins of the Universe, whose age is more than 12 billion years.

In protogalaxies it had a lot of very massive stars. In a few tens of millions of years, the majority of them exploded. These explosions have enriched gas clouds of heavy chemical elements. Therefore, in the galactic disk is not born stars such as the halo - they contained hundreds of times more metal. In addition, these explosions have created a powerful galactic vortex that warmed up gas and swept it off the protogalaxies. There has been a division of the gas mass and dark matter. It was an important stage in the formation of galaxies, not considered before in any model.

Meanwhile, the dark halos are increasingly faced with each other. This protogalaxy stretched or broken up. About these catastrophes resemble chains of stars, preserved in the halo of the Milky Way since the "youth". Studying their location, can be assessed events in that era. Gradually these stars formed an extensive sphere - seen by us halo. As the cooling gas inside it penetrated the clouds. Their angular momentum is conserved, so they are not compressed into one single point, and formed a spinning disk. All this took place more than 12 billion years ago. Now the gas is compressed as described in the model ELS.

At this time, image and "bulge" of the Milky Way - its middle part, which resembles an ellipsoid. Bulge consists of very old stars. Obviously, it emerged at the confluence of the largest protogalaxies, the longest hold gas clouds. In the middle of it turned out to be a tiny neutron stars and black holes - relics of exploding supernovae. They merge with each other, simultaneously absorbing gas flows. Perhaps it was born a huge black hole, now residing at the center of our galaxy.

The history of the Milky Way is much more chaotic than previously thought. Our home galaxy, impressive even by the standards of space, was formed after a series of strokes and mergers - after a series of cosmic catastrophes. Traces of those ancient events can be found today.

For example, not all the stars of the Milky Way orbit the galactic center. Obviously, over billions of years of its existence, our galaxy "swallowed up" a lot of travel. Age every ten stars in the galactic halo - less than 10 billion years. By the time the Milky Way has been formed. Perhaps this - the remnants of once captured dwarf galaxies. The group of British scientists from the Institute of Astronomy (Cambridge), headed by Gerard Gilmore estimated that the Milky Way apparently has absorbed between 40 and 60 dwarf galaxies such as Karina.

In addition, the Milky Way attracts huge masses of gas. So, in 1958 Dutch astronomers noticed the halo of many small spots. In actual fact they were gas clouds, which consisted mainly of hydrogen atoms and raced towards the galactic disk.

Our galaxy it curbs your appetite to continue. Obviously, it will swallow the nearest dwarf galaxies to us - Fornax, Karina and maybe, sextant, and then merge with the Andromeda nebula. Around the Milky Way - this insatiable "star cannibal" - will become a desert.