W Ursae Minoris is an

eclipsing binary A binary star or binary star system is a Star system, system of two stars that are gravity, gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved ...

star system in the constellation

Ursa Minor Ursa Minor (, contrasting with Ursa Major), also known as the Little Bear, is a constellation located in the far northern celestial hemisphere, northern sky. As with the Great Bear, the tail of the Little Bear may also be seen as the handle of ...

. Its

apparent magnitude Apparent magnitude () is a measure of the Irradiance, brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction (astronomy), ...

ranges from 8.51 to 9.59 over 1.7 days as one star passes in front of the other relative to observers on Earth. The combined spectrum of the system is A1/2V. Slight changes in the orbital period suggest that there is a third component of the multiple star system, most likely a red dwarf, with an orbital period of . Another study suggests that the third star has a minimum mass of and an orbit of about . The two main stars are currently thought to have masses of and respectively. Models of their

evolution Evolution is the change in the heritable Phenotypic trait, characteristics of biological populations over successive generations. It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, re ...

and

mass transfer Mass transfer is the net movement of mass from one location (usually meaning stream, phase, fraction, or component) to another. Mass transfer occurs in many processes, such as absorption, evaporation, drying, precipitation, membrane filtra ...

suggest that the secondary star was initially the more massive of the two and that it has lost mass to what is now the primary as well as losing mass completely from the system. The two stars have also spiralled in towards each other over the few hundred million years since they formed.

References

{{Stars of Ursa Minor Ursa Minor Eclipsing binaries Ursae Minoris, W 150265 079069 A-type main-sequence stars G-type subgiants