The mystery itself a huge star R136a1!

In the Tarantula Nebula (NGC 2070), which in the galaxy, the Large Magellanic Cloud, there is a massive star cluster R136 with the biggest and brightest star with all known to mankind.

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R136a1 — Titanic scale of an object with a surface temperature of more than 50 000 K, which at birth weighed 320 suns. And even today, after a million years of intense mass loss, the star is about 265 times more massive than our sun. Thus, it is superior to the sun luminosity at 8.7 million times, an enormous light pressure on its surface. The pressure is, of course, leads to the release into the environment of considerable substance — strong stellar wind.

The problem with R136a1 first is that, according to existing theories of stellar evolution, these stars can not be: no star can not be formed (in fact become a star) with a mass greater than 150 solar masses. A R136a1 at birth more than twice exceeded that limit. That is why it is classified as hyper giants, that is, belongs to a class of stars that appeared after having been found larger supergiant star (whom astronomers once led into his classification of the greatest luminaries).

In the Large Magellanic Cloud is only 10 billion stars — ten times less than in the Milky Way. However, there are many regions of intense star formation, among which the most striking is the Doradus Nebula, greatly superior in its activities, any known region of our Galaxy. It has a four-star Wolf — Rayet stars, and it is very much a mystery. Total number of such stars in our galaxy, 230 (less than one in a billion), and the Large Magellanic Cloud — 100 (one to one hundred million).

The reasons for such a high concentration of Wolf — Rayet stars in the Large Magellanic Cloud in general and their abundance in the Doradus nebula in particular, until recently, remained in doubt. Now a team of researchers from the Institute of Astronomy. Argelandera in Bonn (Germany), under the overall supervision of Sambarana Banerjee (Sambaran Banerjee) suggested a way out of the situation with an unusually massive R136a1 and all cluster R136. According to astronomers, the fact that the stars of spectral type O (hypergiants) formed there are very close to each other in compact binary systems. Therefore, in the future, part of them as a result of the gravitational interaction between the beginning of the spiral closer, eventually colliding and forming a star colossal mass and luminosity, such as R136a1 etc.

The scientists simulated the relative positions and interactions of stars in the nebula Dorado and cluster R136, based on its initial composition of 170 million stars with a mass not exceeding 150 solar (which is to detect hypergiants considered the classical limit). Then they let the model for 3.5 million years to evolve, and found a curious, namely some cases merging stars, 150 solar masses, which are in compact binary systems.

"When the calculations are finished, light-heavyweights have ceased to be a mystery, — says Mr. Banerjee. — Let's imagine two relatively big stars that rotate around each other. If their initial orbits were moderately elongated, the shining face and form one huge star. "

As you can see, it's simple: mass limit of normal primary stars retained, and anything above 150 solar masses — the result of mergers, as it were "secondary" star. Thus, hyper giants like R136a1 are just curious exception, not the rule. So what, and "wolves" (the facts of astronomical observations) are full, and the "sheep" (astronomical theories) are safe?

Almost. Practical study of systems of blue giants in our Galaxy has shown that 70% of them exist in the systems of binary stars, very massive with a second partner. Moreover, even those 30% that does not have a star-mates, it seems that once they had — and that's why drift through the galaxy with great speed, which developed after the explosion of the second star of his system, which has become a supernova.

In other words, the giants in binary systems — a phenomenon rather regular, not random. And that means that the chances of finding them outside of the Large Magellanic Cloud are quite large. Until now, it did not occur to a large extent because most hypergiants exist in dense star clusters and nebulae, where they are very difficult to observe: prevents the light of neighboring stars. However, with the progress of astronomical instruments we can expect a significant number of discoveries such "heavyweights".

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