Stellar mass loss is a phenomenon observed in

star A star is an astronomical object comprising a luminous spheroid of plasma held together by its gravity. The nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night, but their immense distances from Earth make ...

s. All stars lose some mass over their lives at widely varying rates. Triggering events can cause the sudden ejection of a large portion of the star's mass. Stellar mass loss can also occur when a star gradually loses material to a binary companion or into interstellar space.

Causes

A number of factors can contribute to the loss of mass in giant stars, including: *Gravitational attraction of a binary companion *

Coronal mass ejection A coronal mass ejection (CME) is a significant release of plasma and accompanying magnetic field from the Sun's corona into the heliosphere. CMEs are often associated with solar flares and other forms of solar activity, but a broadly accep ...

-type events *Ascension to

red giant A red giant is a luminous giant star of low or intermediate mass (roughly 0.3–8 solar masses ()) in a late phase of stellar evolution. The outer atmosphere is inflated and tenuous, making the radius large and the surface temperature around or ...

or red supergiant status

Solar wind

The Sun, a low-mass star, loses mass due to the

solar wind The solar wind is a stream of charged particles released from the upper atmosphere of the Sun, called the corona. This plasma mostly consists of electrons, protons and alpha particles with kinetic energy between . The composition of the ...

at a very small rate,

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 ...

es per year.

Gravitational mass loss

Often when a star is a member of a pair of close-orbiting

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 ...

s, the tidal attraction of the gasses near the center of mass are sufficient to pull gas from one star onto its partner. This effect is especially prominent when the partner is a

white dwarf A white dwarf is a stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very dense: its mass is comparable to the Sun's, while its volume is comparable to the Earth's. A white dwarf's faint luminosity comes ...

neutron star A neutron star is the collapsed core of a massive supergiant star, which had a total mass of between 10 and 25 solar masses, possibly more if the star was especially metal-rich. Except for black holes and some hypothetical objects (e.g. w ...

, or

black hole A black hole is a region of spacetime where gravity is so strong that nothing, including light or other electromagnetic waves, has enough energy to escape it. The theory of general relativity predicts that a sufficiently compact mass can defo ...

Mass ejection

Certain classes of stars, especially Wolf-Rayet stars are sufficiently massive and distended that their hold on their upper layers is rather weak. Often, events such as

solar flares A solar flare is an intense localized eruption of electromagnetic radiation in the Sun's atmosphere. Flares occur in active regions and are often, but not always, accompanied by coronal mass ejections, solar particle events, and other sola ...

and

coronal mass ejections A coronal mass ejection (CME) is a significant release of plasma and accompanying magnetic field from the Sun's corona into the heliosphere. CMEs are often associated with solar flares and other forms of solar activity, but a broadly accepted t ...

will then be sufficiently powerful to blast some of the upper material into space.

Red giant mass loss

Stars which have entered the red giant phase are notorious for rapid mass loss. As above, the gravitational hold on the upper layers is weakened, and they may be shed into space by violent events such as the beginning of a

helium flash A helium flash is a very brief thermal runaway nuclear fusion of large quantities of helium into carbon through the triple-alpha process in the core of low mass stars (between 0.8 solar masses () and 2.0 ) during their red giant phase (the Sun i ...

in the core. The final stage of a red giant's life will also result in prodigious mass loss as the star loses its outer layers to form a

planetary nebula A planetary nebula (PN, plural PNe) is a type of emission nebula consisting of an expanding, glowing shell of ionized gas ejected from red giant stars late in their lives. The term "planetary nebula" is a misnomer because they are unrelate ...

References

{{Reflist *Seeds, Michael A., ''Astronomy: The Solar System and Beyond'', Brooks/Cole 2005

External links

Simulation of a Red Supergiant displaying instability and mass loss
Stellar phenomena