object

wolf rayet star

A massive, hot star with strong stellar winds and stripped outer layers, a possible hard-radiation source.
78 related articles

Description

A Wolf–Rayet star is a massive, evolved star that has lost its outer hydrogen envelope, exposing its hot, helium-burning core. These stars are among the most luminous and hottest objects in the universe, with surface temperatures ranging from 30,000 to over 200,000 Kelvin. They are characterized by intense stellar winds that eject mass at rates millions of times higher than the Sun's, stripping the star's outer layers and enriching the surrounding interstellar medium with heavy elements like carbon, nitrogen, and oxygen. Wolf–Rayet stars are short-lived, lasting only a few hundred thousand years before ending in a supernova explosion.

History

The first Wolf–Rayet stars were discovered in 1867 by French astronomers Charles Wolf and Georges Rayet, who noticed stars with unusually broad emission lines in their spectra. Their true nature as evolved, stripped massive stars was not understood until the mid-20th century, with the development of stellar evolution theory and spectroscopy.

How it works

A Wolf–Rayet star begins as a very massive star (over 25 solar masses) that burns hydrogen in its core. After exhausting hydrogen, the core contracts and heats up, igniting helium fusion. The enormous luminosity of the core drives a powerful radiation pressure that pushes the outer layers outward. Because the outer envelope is loosely bound, this pressure drives a dense, fast stellar wind that blows away the hydrogen envelope over time. What remains is the bare helium-burning core, which is extremely hot and emits most of its energy in the ultraviolet and X-ray parts of the spectrum. The strong winds also create characteristic broad emission lines in the star's spectrum, which are used to identify these objects.

In practice

Wolf–Rayet stars are important in astrophysics as progenitors of certain types of supernovae and gamma-ray bursts, and they are used as tracers of star formation in distant galaxies.

Fun fact

The famous star Eta Carinae, which had a massive eruption in the 19th century, is thought to be a binary system that may contain a Wolf–Rayet star.

Concept graph →

Related articles · 79

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