A colliding-wind binary is a

binary star A binary star 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 using a telescope as separate stars, in ...

system in which the two members are massive stars that emit powerful, radiatively-driven

stellar wind A stellar wind is a flow of gas ejected from the upper atmosphere of a star. It is distinguished from the bipolar outflows characteristic of young stars by being less collimated, although stellar winds are not generally spherically symmetric. ...

s. The location where these two winds collide produces a strong shock front that can cause radio,

X-ray X-rays (or rarely, ''X-radiation'') are a form of high-energy electromagnetic radiation. In many languages, it is referred to as Röntgen radiation, after the German scientist Wilhelm Conrad Röntgen, who discovered it in 1895 and named it ' ...

and possibly

synchrotron radiation Synchrotron radiation (also known as magnetobremsstrahlung radiation) is the electromagnetic radiation emitted when relativistic charged particles are subject to an acceleration perpendicular to their velocity (). It is produced artificially in ...

emission. Wind compression in the bow shock region between the two stellar winds allows dust formation. When this dust streams away from the orbiting pair, it can form a pinwheel

nebula A nebula ('cloud' or 'fog' in Latin; pl. nebulae, nebulæ or nebulas) is a distinct luminescent part of interstellar medium, which can consist of ionized, neutral or molecular hydrogen and also cosmic dust. Nebulae are often star-forming regio ...

of spiraling dust. Such pinwheels have been observed in the Quintuplet Cluster The archetype of such a colliding-wind binary system is

WR 140 WR 140 is a visually moderately bright Wolf–Rayet star placed within the spectroscopic binary star, SBC9 1232, whose primary star is an evolved spectral class O4–5 star. It is located in the constellation of Cygnus, lying in the sk ...

(HD 193793), which consists of a 20

solar mass The solar mass () is a standard unit of mass in astronomy, equal to approximately . It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxies and black holes. It is approximately equal to the mass o ...

() Wolf-Rayet star orbiting about a ,

spectral class In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting th ...

O4-5 main sequence star every 7.9 years. The high

orbital eccentricity In astrodynamics, the orbital eccentricity of an astronomical object is a dimensionless parameter that determines the amount by which its orbit around another body deviates from a perfect circle. A value of 0 is a circular orbit, values b ...

of the pair allows astronomers to observe changes in the colliding wind region as their separation varies. Another prominent example of a colliding-wind binary is thought to be

Eta Carinae Eta Carinae (η Carinae, abbreviated to η Car), formerly known as Eta Argus, is a stellar system containing at least two stars with a combined luminosity greater than five million times that of the Sun, located around distant in th ...

, one of the most luminous objects in the

Milky Way The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked ey ...

galaxy. The first colliding-wind binary to be detected in the X-ray band outside the Milky Way galaxy was

HD 5980 HD 5980 is a multiple star system on the outskirts of NGC 346 in the Small Magellanic Cloud (SMC) and is one of the brightest stars in the SMC. HD 5980 has at least three components among the most luminous stars known: the unusual pr ...

, located in the

Small Magellanic Cloud The Small Magellanic Cloud (SMC), or Nubecula Minor, is a dwarf galaxy near the Milky Way. Classified as a dwarf irregular galaxy, the SMC has a D25 isophotal diameter of about , and contains several hundred million stars. It has a total mass of ...

References

* {{multi-star-stub

See also

References