The terms galactic corona and gaseous corona have been used in the first decade of the 21st century to describe a hot, ion

Ion

An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...

ised, gaseous component in the Galactic halo

Galactic halo

The term galactic halo is used to denote an extended, roughly spherical component of a galaxy, which extends beyond the main, visible component. It can refer to any of several distinct components which share these properties:* the galactic spheroid...

 of the Milky Way

Milky Way

The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...

. A similar body of very hot and tenuous gas in the halo of any spiral galaxy

Spiral galaxy

A spiral galaxy is a certain kind of galaxy originally described by Edwin Hubble in his 1936 work The Realm of the Nebulae and, as such, forms part of the Hubble sequence. Spiral galaxies consist of a flat, rotating disk containing stars, gas and dust, and a central concentration of stars known as...

 may also be described by these terms.

This coronal gas may be sustained by the galactic fountain, in which superbubble

Superbubble

Superbubble is the astronomical term used to describe a cavity hundreds of light years across filled with 106 K gas blown into the interstellar medium by multiple supernovae and stellar winds...

s of ionised gas from supernova remnant

Supernova remnant

A supernova remnant is the structure resulting from the explosion of a star in a supernova. The supernova remnant is bounded by an expanding shock wave, and consists of ejected material expanding from the explosion, and the interstellar material it sweeps up and shocks along the way.There are two...

s expand vertically through galactic chimneys into the halo. As the gas cools, it is pulled back into the galactic disc of the galaxy by gravitational forces.

See also

• Galaxy formation and evolution
  Galaxy formation and evolution
  The study of galaxy formation and evolution is concerned with the processes that formed a heterogeneous universe from a homogeneous beginning, the formation of the first galaxies, the way galaxies change over time, and the processes that have generated the variety of structures observed in nearby...
  
  
• Galactic coordinate system
  Galactic coordinate system
  The galactic coordinate system is a celestial coordinate system which is centered on the Sun and is aligned with the apparent center of the Milky Way galaxy. The "equator" is aligned to the galactic plane...
  
  
• Galactic bulge
  Bulge (astronomy)
  In astronomy, a bulge is a tightly packed group of stars within a larger formation. The term almost exclusively refers to the central group of stars found in most spiral galaxies...
  
  
• Disc galaxy
  Disc galaxy
  Disc galaxies are galaxies which have discs, a flattened circular volume of stars. These galaxies may, or may not include a central non-disc-like region .Disc galaxy types include* spiral galaxies** barless spiral galaxies...
  
  
  • Spiral arm
• Galactic halo
  Galactic halo
  The term galactic halo is used to denote an extended, roughly spherical component of a galaxy, which extends beyond the main, visible component. It can refer to any of several distinct components which share these properties:* the galactic spheroid...
  
  
• Galactic spheroid

External links

• THE GALACTIC CORONA, Jerry Bonnell, 1995
• Absorption Line Studies in the Halo, Philipp Richter, 2003
• Multi-phase High-Velocity Clouds toward HE 0226-4110 and PG 0953+414, Andrew J. Fox et al., 2005
• Galactic Corona or Local Group Intergalactic Medium?, Rik J. Williams, Smita Mathur, & Fabrizio Nicastro, 2005
• NGC 5746: Detection of Hot Halo Gets Theory Out of Hot Water