W Latest scientific article Researchers from the University of Toronto report the discovery of an entire population of massive stars that have been stripped of their hydrogen envelope by a second star in a binary system. Everything indicates that such stars, which no longer have their thick, extended hydrogen envelopes, may be hot helium stars that will over time explode as hydrogen-poor supernovae in the process of core collapse. Furthermore, such binary systems can evolve over time into binary systems consisting of two neutron stars that merge with each other over time.
Scientists have long suspected that, on average, one in three massive stars in binary systems is completely devoid of a hydrogen shell. The problem is that the search was able to find only one candidate for such a star. Therefore, the observations did not match the theory.
But now everything has changed. We were able to find a complete set of these stars.
Such massive, unenveloped stars in binary systems have been talked about for a long time. Theoretical systems of this type have provided a possible explanation for why a third of supernovae generated by core collapse contain much less hydrogen than a typical red supergiant explosion. The authors of the latest study suggest that the newly discovered stars will eventually explode as hydrogen-poor supernovae.
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Scientists believe that at least several of the objects in their sample are abstract stars orbiting a center of mass shared with a neutron star or black hole. The development of such objects will soon lead them to the stage of a binary system consisting of two neutron stars or a neutron star and a black hole. These objects combine over time to form one huge body.
How does the hydrogen shell disappear?
As the massive star develops into a red giant, its size increases significantly. Inevitably, at its outer edge, the gravitational force of the star’s core is relatively weak, which is relatively rare. In such conditions, it is relatively easy for a nearby neutron star to grab some of this matter by gravity, which gravitates toward the neutron star, gradually reducing the mass of the red giant. impact? After some time – from tens to several hundred thousand years – all that remained of the red giant was its superheated helium core.
The problem is that such stars devoid of hydrogen are difficult to find, because the radiation they emit is weak and outside the visible radiation range. To find such stars, the researchers decided to start by looking in ultraviolet light. It is in this range that very hot stars usually emit most of their radiation. Using the Swift telescope, the researchers looked at millions of stars in the Large and Small Magellanic Clouds, the two closest galaxies to us that can be seen with the naked eye from the Southern Hemisphere. In this way, the first dozens of stars of this type were found. However, this is only the beginning of the research. Scientists say they are already planning similar searches in other nearby galaxies, but also in the Milky Way. The research will be conducted, among others, using the Hubble Space Telescope, the Chandra X-ray Observatory, and the Magellan telescopes. We can expect more facilities of this type soon.
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