The Attraction Of The White Dwarf Pulled Its Neighbor In The Double Star Into A Drop
In the constellation of Gemini, astronomers have discovered an unusual double star. One of its components acquired the shape of a drop under the influence of the neighbor's attraction. After 70 million years, they will merge, resulting in a supernova explosion, the researchers write in the scientific journal Nature Astronomy.
"On the one hand, a white dwarf can absorb a lot of matter so that the plasma of its neighbor begins to flow directly to its surface. If this does not happen, the stars will gradually get closer and merge. In both cases, a supernova explosion will occur," said Ingrid Pelisoli, one of the authors of the article, a researcher at the University of Warwick.
Astronomers call white dwarfs the cores of "burnt out" small stars that do not have their energy sources. They occur in the last stages of the life of stars that are no more than ten times heavier than the Sun. Such stars do not explode as supernovas but shed their outer shells. As a result, a nebula is formed, which is "illuminated" from the inside by its former core.
The mass of white dwarfs cannot exceed the so-called Chandrasekhar limit. When it reaches it, the matter of the core of the burned-out star reaches such a density that its atoms cease to exist, and the white dwarf turns into a neutron star. It is believed that this limit is about 1.44 times the mass of the Sun, but its exact value has not yet been established.
Almost all known white dwarfs are very far from this limit. However, as a result of the merger of two similar stars, as well as a white dwarf and an ordinary star, this limit is often exceeded. As a result, a supernova of the first type explodes, and almost all the matter of both stars is converted into light and energy.
Pelisoli and her colleagues have discovered a double star that will generate a similar flare shortly (by astronomical standards). Analyzing the data collected by the TESS orbiting telescope, they drew attention to the star HD265435. It is located in the constellation Gemini at a distance of 1.5 thousand light-years from Earth.
The brightness of this star increased and decreased. As a rule, such behavior indicates the existence of one or more planets in the vicinity of the Sun. However, in this case, it turned out to be a sign of the exotic structure of this star system.
The change in brightness was since HD265435 is a double star. It consists of an invisible white dwarf and a so-called hot sub-dwarf. This is what scientists call very compact and hot luminaries that arise after the outer shells are dropped by some types of large stars in the last stages of their existence.
This sub-dwarf turned out to have an atypical shape for a star: it was elongated into a drop. Scientists believe that this was due to the attraction of a white dwarf, which made one revolution around the second star in less than 100 minutes. Scientists ' calculations show that the distance between these stars is continuously decreasing, as they lose energy to the radiation of gravitational waves.
In about 70 million years, both stars will merge. As a result, an object at least 1.65 times heavier than the Sun will appear. This feature of the HD265435 star system makes it one of the closest "embryos" of the first type of supernovae to Earth, further study of which will help scientists understand how often mergers of white dwarfs and hot sub-dwarfs generate such outbursts.