WR 25

WR 25 (HD 93162) is a Wolf-Rayet star in the turbulent star forming region Carina Nebula, about 7,500 light-years from Earth. It has a companion and resides in the Trumpler 16 cluster.

The primary star is notable for being the most luminous known star in the Milky Way Galaxy, substantially brighter than its nearby neighbor Eta Carinae, although it is unclear what contribution is from the companion. It is approximately 6.3 million times brighter than the Sun and illuminates the far southern end of the Trumpler 16 cluster. The model used to derive the stellar parameters is unsuitable for use in binary systems with the authors noting that the companion contributes more than 15% of the system luminosity, so the luminosity is highly uncertain. Earlier estimates based on measurements of the ionising flux produced values around 1.5 million times the sun, with correspondingly lower estimates for other physical data.

The companion is assumed to be a young hot massive star, similar to other known WR+O or WR+WR binaries, where colliding stellar winds produce the hard X-rays that led to suspicion about the binary status long before the 208 day orbital period was detected.