WR 133 is a visually moderately bright Wolf-Rayet star. It is a

spectroscopic binary A binary star or binary star system is a system of two stars that are 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 as separate stars us ...

system containing a Wolf-Rayet primary and a class O

supergiant Supergiants are among the most massive and most luminous stars. Supergiant stars occupy the top region of the Hertzsprung–Russell diagram, with absolute visual magnitudes between about −3 and −8. The temperatures of supergiant stars range ...

secondary. It is in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The first constellati ...

of Cygnus, lying in the sky at the centre of the triangle formed by β and

γ Cygni Gamma Cygni is a star in the northern constellation of Cygnus, forming the intersection of an asterism of five stars called the Northern Cross. It is officially named Sadr , gamma Cygni is its Bayer designation, which that is Latiniz ...

, near η Cygni. It is the brightest member of the sparse

open cluster An open cluster is a type of star cluster made of tens to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way galaxy, and ...

NGC 6871. WR 133 is one of the brightest Wolf Rayet (WR) stars in the

northern hemisphere The Northern Hemisphere is the half of Earth that is north of the equator. For other planets in the Solar System, north is defined by humans as being in the same celestial sphere, celestial hemisphere relative to the invariable plane of the Solar ...

, slightly brighter than WR 140 which also in Cygnus. The WR star is typically identified as the primary, being more luminous, and dominating the spectrum. However, the supergiant secondary is more massive and visually brighter. The primary star is a WN5 nitrogen-rich WR star and the secondary has a spectral type of O9I. The orbit is moderately eccentric and has a

period Period may refer to: Common uses * Period (punctuation) * Era, a length or span of time *Menstruation, commonly referred to as a "period" Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (o ...

of , which has been determined from the velocity variations observed with the component's spectral lines, mostly from the He

emission line A spectral line is a weaker or stronger region in an otherwise uniform and continuous spectrum. It may result from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies. Spectral lines are often used ...

s at for the WR primary, and helium and oxygen

absorption line Absorption spectroscopy is spectroscopy that involves techniques that measure the absorption (electromagnetic radiation), absorption of electromagnetic radiation, as a function of frequency or wavelength, due to its interaction with a sample. Th ...

s for the primary. This is the first WN-type WR star to have its mass dynamically determined from orbital motion, although the precision is hampered by the nearly face-on orientation of the orbit. WR 133 is listed as a Wolf-Rayet

variable star A variable star is a star whose brightness as seen from Earth (its apparent magnitude) changes systematically with time. This variation may be caused by a change in emitted light or by something partly blocking the light, so variable stars are ...

and has been given the

variable star designation In astronomy, a variable-star designation is a unique identifier given to variable stars. It extends the Bayer designation format, with an identifying label (as described below) preceding the Latin genitive of the name of the constellation in whic ...

V1676 Cyg in the

General Catalogue of Variable Stars The General Catalogue of Variable Stars (GCVS) is a list of variable stars in the Milky Way Galaxy. Its first edition, containing 10,820 stars, was published in 1948 by the Academy of Sciences of the USSR, edited by and Pavel Parenago. Second a ...

. Its

visual magnitude Apparent magnitude () is a measure of the 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 of the object's light ca ...

varies between 6.75 and 6.84.

References

{{Stars of Cygnus Cygnus (constellation) Wolf–Rayet stars J20055731+3547181 190918 Spectroscopic binaries Cygni, V1676 BD+35 3953 099002 O-type supergiants