One orbit in 20 minutes: Astronomers find a binary system with an ultra-short period

Using TMTS, an international team of researchers has discovered a binary star with an ultra-short orbital period. It is only 20.5 minutes. 

A system consisting of a white dwarf and an ordinary star in the artist’s image. Source: Marisa Grove/Institute of Astronomy

The theory of the evolution of binary stars predicts the existence of binary systems with ultra-short orbital periods. However, until recently, astronomers were aware of only four systems of this type with orbital periods of less than an hour. 

Now this list has increased to five. During the survey carried out using TMTS, the researchers managed to find a previously unknown binary system J0526, located 2,760 light-years from Earth. It consists of a visible star with a mass of 0.33 solar and a white dwarf with a mass equal to 0.73 solar masses. They make one orbit around each other in just 20.5 minutes.

The calculations performed by the researchers showed that in the future, they would get so close that the white dwarf would begin to absorb the matter of its companion. This will lead to the fact that the orbital period will decrease even more — at first to 14, and then to 9 minutes. However, after losing a certain part of its mass, the star will expand, which will lead to an increase in the orbital period. 

In any case, even if the white dwarf completely absorbs its companion, their combined mass is not enough to overcome the Chandrasekhar limit (1.44 solar masses). This means that it is not destined to explode and turn into a neutron star.

According to

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