Scientists hypothesized that the Sun is part of a binary system. The assumption was based on a study of the periods of mass extinctions that occur on Earth, where scientists have seen the periodic structure is repeated every 27 million years. Assuming that a companion of the Sun with a similar orbital period still exist, he approached, may disturb the movement of space objects located in the Kuiper Belt, and the Oort cloud, sending some of them on a collision course with our planet. Being a brown or white dwarf located at a distance of 1.5 light-years of Earth, the companion star is quite not easy to detect. Another fact in favor of a hypothetical star-nemesis is the orbit of Sedna, a dwarf planet, orbiting at a very great distance from the Sun. Although this theory has several contentious issues. Nemesis, turning far enough away from our star, has likely unstable orbit, which is subject to the influence of other stars, and then there is no periodicity. In addition, the frequency of extinctions itself is still questionable. Some global extinction does not fit into this scheme; others do not in any way associated with impact craters. In addition, with the help of a telescope WISE was open 20 brown dwarfs within 20 light years, Nemesis is not found, which is characteristic of several other reviews.