Galactic corona

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The terms galactic corona and gaseous corona have been used in the first decade of the 21st century to describe a hot, ionised, gaseous component in the galactic halo of the Milky Way. A similar body of very hot and tenuous gas in the halo of any spiral galaxy may also be described by these terms.

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Current hypothetical scenario

The hypothetical source of the galactic halo of coronal gas may be the cumulative output of many “galactic fountains” in the galactic disc ejecting hot gas.

The hypothesis is that a single supernova and then its supernova remnant both produce hot ionized gas that supplies an individual “galactic fountain”. The expelled material forms a giant bubble of high-pressure, low density, hot gas in the denser, cooler gas and dust of the galactic disc. At least some of those bubbles extend high or low enough, vertically, to pierce through the denser disk, and form “chimneys” which exhaust the hot gas into the halo, analogous to a terrestrial geyser spewing out water and steam that is much hotter and much less dense than the surrounding earth, heated by a source hidden deep below.

As the expelled gas in the galactic corona cools, it falls back into the galactic disc, guided by the disc's own gravitational attraction, enriching the gas and dust in the disc with the heavy elements (loosely termed “metals” by astronomers) which were produced in supernova precursors, and during supernova explosions.

Current research

Galactic coronas have been and are currently being studied extensively, in the hope of gaining a further understanding of galaxy formation. [1] [2] However, considering how galaxies differ in shape and size, no particular theory has been able to adequately explain how all galactic coronas are formed and maintained. [3]

See also

Related Research Articles

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In astrobiology and planetary astrophysics, the galactic habitable zone is the region of a galaxy in which life might most likely develop. The concept of a galactic habitable zone analyzes various factors, such as metallicity and the rate and density of major catastrophes such as supernovae, and uses these to calculate which regions of a galaxy are more likely to form terrestrial planets, initially develop simple life, and provide a suitable environment for this life to evolve and advance. According to research published in August 2015, very large galaxies may favor the birth and development of habitable planets more than smaller galaxies such as the Milky Way. In the case of the Milky Way, its galactic habitable zone is commonly believed to be an annulus with an outer radius of about 10 kiloparsecs (33,000 ly) and an inner radius close to the Galactic Center.

NGC 4636 Elliptical galaxy in the constellation Virgo

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NGC 4302 Edge-on spiral galaxy in the constellation Coma Berenices

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References

  1. Pedersen, K.; et al. (X-ray: NASA / CXC / U. Copenhagen; optical: Palomar DSS) (2006). Detection of hot halo gets theory out of hot water. Chandra Space Telescope (composite optical & X-ray image with expository caption). NGC 5746. Harvard University. Retrieved 19 December 2020.
  2. Williams, Rik J.; Mathur, Smita & Nicastro, Fabrizio (2005). "Galactic corona or Local Group intergalactic medium?". arXiv: astro-ph/0511621 .
  3. Hille, Karl (22 September 2017). "Hubble's cool galaxy with a hot corona". NASA.gov. Retrieved 25 September 2017.