M82 Galaxy from the Mount Lemmon SkyCenter Schulman Telescope courtesy Adam Block

A galactic superwind, or just galactic wind, is a high velocity

stellar wind A stellar wind is a flow of gas ejected from the stellar atmosphere, 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 spheri ...

emanating from either newly formed massive stars, spiral density waves, or as the result of the effects of

supermassive black hole A supermassive black hole (SMBH or sometimes SBH) is the largest type of black hole, with its mass being on the order of hundreds of thousands, or millions to billions, of times the mass of the Sun (). Black holes are a class of astronomical ...

s. They are normally observed in

starburst galaxies A starburst galaxy is one undergoing an exceptionally high rate of star formation, as compared to the long-term average rate of star formation in the galaxy, or the star formation rate observed in most other galaxies. For example, the star format ...

Description

Galactic winds are strong stellar winds made up of charged particles,

ejecta Ejecta (; ) are particles ejected from an area. In volcanology, in particular, the term refers to particles including pyroclastic rock, pyroclastic materials (tephra) that came out of a explosive eruption, volcanic explosion and magma eruption v ...

, and varying amounts of hot and cool gas, interacting with enough force that the ejecta's

kinetic energy In physics, the kinetic energy of an object is the form of energy that it possesses due to its motion. In classical mechanics, the kinetic energy of a non-rotating object of mass ''m'' traveling at a speed ''v'' is \fracmv^2.Resnick, Rober ...

is converted to

thermal energy The term "thermal energy" is often used ambiguously in physics and engineering. It can denote several different physical concepts, including: * Internal energy: The energy contained within a body of matter or radiation, excluding the potential en ...

. The resulting effect is a massive gust of rapidly expanding super-heated gases that can span the length of a galaxy. In galaxies with active

galactic nuclei An active galactic nucleus (AGN) is a compact region at the center of a galaxy that emits a significant amount of energy across the electromagnetic spectrum, with characteristics indicating that this luminosity is not produced by the stars. Such e ...

, galactic winds can also be driven by the effects of super-massive black holes. Galactic winds are considered an important function in the evolution of a galaxy. The winds cause an outflow of gas and other material into the

halo HALO, halo, halos or haloes may refer to: Most common meanings * Halo (optical phenomenon) * Halo (religious iconography), a ring of light around the image of a head * ''Halo'' (franchise), a sci-fi video game series (2001–2021) Arts and en ...

of a galaxy, while also facilitating the spread of

metals A metal () is a material that, when polished or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. These properties are all associated with having electrons available at the Fermi level, as against no ...

around a galaxy. Galactic winds are also capable of blowing material out of a galaxy entirely and into the

intergalactic medium Intergalactic may refer to: * "Intergalactic" (song), a song by the Beastie Boys * ''Intergalactic'' (TV series), a 2021 UK science fiction TV series * Intergalactic space * Intergalactic travel, travel between galaxies in science fiction and ...

Formation

Superwinds are theorized to form in compact

in which star growth is much higher than in other types of galaxies. This accelerated star growth results in more prevalent stellar winds being present in starburst galaxies. Superwinds form when ejecta released either by supernovae or stellar winds collide with such force that the

shock Shock may refer to: Common uses Healthcare * Acute stress reaction, also known as psychological or mental shock ** Shell shock, soldiers' reaction to battle trauma * Circulatory shock, a medical emergency ** Cardiogenic shock, resulting from ...

from the impact converts the kinetic energy of the ejecta into thermal energy. The violent conversion from kinetic to thermal energy prevents a significant amount of energy from being radiated away. This in turn creates an incredibly hot bubble of gas that is under much greater pressure than it surroundings are. Eventually the gas bubble will expand to encompass other particles of ejected gases, further increasing the force and size of its expansion. This "snowplow" effect results in a gust of

and gas that can span the width of a galaxy. It has been theorized that superwinds can potentially be traveling at a velocity of several thousand kilometers per second by the time they enter the

References

Stellar evolution Solar phenomena Stellar phenomena

Description

Formation

See also

References