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Encyclopedia > Galactic center

The Galactic Center is the rotational center of the Milky Way galaxy. It is located about 7.6 kiloparsecs (24,800 LY) away from the Earth,[1] in the direction of the constellation Sagittarius, where the Milky Way appears brightest. Scientists hypothesize that a supermassive black hole lies in the Galactic Center of the Milky Way, and most (if not all) other galaxies. The Galactic Center Saga is a series of books by author Gregory Benford detailing a galactic war between mechanical and biological life. ... In astronomy, a bulge is a huge, tightly packed group of stars. ... For other uses, see Milky Way (disambiguation). ... For other uses, see Galaxy (disambiguation). ... A parsec is the distance from the Earth to an astronomical object which has a parallax angle of one arcsecond. ... A light-year or lightyear (symbol: ly) is a unit of measurement of length, specifically the distance light travels in vacuum in one year. ... This article is about Earth as a planet. ... This article is about the star grouping. ... For other uses, see Sagittarius. ... Top: artists conception of a supermassive black hole tearing apart a star. ... For other uses, see Milky Way (disambiguation). ...

The Galactic Center as seen by one of the 2MASS infrared telescopes.
The Galactic Center as seen by one of the 2MASS infrared telescopes.

Contents

Image File history File links Size of this preview: 460 × 600 pixelsFull resolution (3910 × 5100 pixel, file size: 11. ... Image File history File links Size of this preview: 460 × 600 pixelsFull resolution (3910 × 5100 pixel, file size: 11. ...

Proof of existence and location

Because of cool interstellar dust along the line of sight, the Galactic Center cannot be studied at visible, ultraviolet or soft X-ray wavelengths. The available information about the Galactic Center comes from observations at gamma ray, hard X-ray, infrared, sub-millimetre and radio wavelengths. Interstellar cloud is the generic name given to an accumulation of gas, plasma and dust in our and other galaxies. ... Visible light redirects here. ... For other uses, see Ultraviolet (disambiguation). ... In the NATO phonetic alphabet, X-ray represents the letter X. An X-ray picture (radiograph) taken by Röntgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz... For other uses, see Wavelength (disambiguation). ... This article is about electromagnetic radiation. ... For other uses, see Infrared (disambiguation). ... Radio frequency, or RF, refers to that portion of the electromagnetic spectrum in which electromagnetic waves can be generated by alternating current fed to an antenna. ...


Coordinates of Galactic Center were first found by Harlow Shapley in his 1918 study of the distribution of the globular clusters. In the Equatorial coordinate system they are: RA 17h45m40.04s, Dec -29° 00' 28.1" (J2000 epoch). Harlow Shapley in his earlier years. ... The Globular Cluster M80 in the constellation Scorpius is located about 28,000 light years from the Sun and contains hundreds of thousands of stars. ... The equatorial coordinate system is probably the most widely used celestial coordinate system, whose equatorial coordinates are: declination () right ascension () -also RA-, or hour angle () -also HA- It is the most closely related to the geographic coordinate system, because they use the same fundamental plane, and the same poles. ... Equatorial Coordinates Right ascension (abbrev. ... In astronomy, declination (abbrev. ... The J2000. ... In astronomy, an epoch is a moment in time for which celestial coordinates or orbital elements are specified. ...


The complex radio source Sagittarius A appears to be located almost exactly at the Galactic Center, and contains an intense compact radio source, Sagittarius A*, which many astronomers believe may coincide with a supermassive black hole at the center of our Galaxy. Accretion of gas onto the black hole, probably involving a disk around it, would release energy to power the radio source, itself much larger than the black hole. The latter is too small to see with present instruments. Radio sources are objects in outer space that emit strong radio waves. ... Sagittarius A (or Sgr A) is a complex radio source at the center of our galaxy, the Milky Way. ... Sagittarius A* (pronounced A-star) is a bright and very compact source of radio emission at the center of the Milky Way Galaxy, part of a larger astronomical feature at that location (Sagittarius A). ... Top: artists conception of a supermassive black hole tearing apart a star. ... See also: Accretion (finance) Accretion is increase in size by gradual addition of smaller parts. ... For other uses, see Black hole (disambiguation). ... Artists conception of a binary star system with one black hole and one main sequence star Unsolved problems in physics: Accretion disc jets: Why do the discs surrounding certain objects, such as the nuclei of active galaxies, emit radiation jets along their polar axes? These jets are invoked by...


Stellar population

The central parsec around Sagittarius A* contains thousands of stars. Although most of them are old red main sequence stars, the Galactic Center is also rich in massive stars. More than 100 OB and Wolf-Rayet stars have been identified there so far. They seem to have all been formed in a single star formation event a few million years ago. The existence of these relatively young (though evolved) stars there was of a surprise to experts, who would have expected the tidal forces from the central black-hole to prevent their formation. This paradox of youth is even more remarkable for stars that are on very tight orbits around Sagittarius A*, such as S2. The scenarios invoked to explain this formation involve either star formation in a massive star cluster offset from the Galactic Center that would have migrated to its current location once formed, or star formation within a massive, compact gas accretion disk around the central black-hole. It is interesting to note that most of these 100 young, massive stars seem to be concentrated within one (according to the UCLA group) or two (according to the MPE group) disks, rather than randomly distributed within the central parsec. This observation however does not allow definite conclusions to be drawn at this point. A parsec is the distance from the Earth to an astronomical object which has a parallax angle of one arcsecond. ... STARS can mean: Shock Trauma Air Rescue Society Special Tactics And Rescue Service, a fictional task force that appears in Capcoms Resident Evil video game franchise. ... Hertzsprung-Russell diagram The main sequence of the Hertzsprung-Russell diagram is the curve where the majority of stars are located in this diagram. ... This article is about the astronomical object. ... OB stars are hot, massive stars stars which form in loosely organized groups called OB associations. ... Wolf-Rayet stars are evolved, hot, massive stars, that exhibit high mass-loss caused by strong stellar winds. ... Star formation is the process by which dense parts of molecular clouds collapse into a ball of plasma to form a star. ... The tidal force is a secondary effect of the force of gravity and is responsible for the tides. ... S2 is a star that is located close to the radio source Sagittarius A*, orbiting it with an orbital period of 15. ... This article or section does not cite its references or sources. ... An accretion disc (or accretion disk) is a structure formed by material falling into a gravitational source. ...


Star formation does not seem to be occurring currently at the Galactic center, although the Circumnuclear Disk of molecular gas that orbits the Galactic center at two parsecs seems a fairly favorable site for star formation. Work presented in 2002 by Antony Stark and Chris Martin mapping the gas density in a 400 light year region around the galactic center has revealed an accumulating ring with a mass several million times that of the Sun and near the critical density for star formation. They predict that in approximately 200 million years there will be an episode of starburst in the galactic center, with many stars forming rapidly and undergoing supernovae at a hundred times the current rate. The starburst may also be accompanied by the formation of galactic jets as matter falls into the central black hole. It is thought that the Milky Way undergoes a starburst of this sort every 500 million years. A light-year or lightyear (symbol: ly) is a unit of measurement of length, specifically the distance light travels in vacuum in one year. ... Sol redirects here. ... Star formation is the process by which dense parts of molecular clouds collapse into a ball of plasma to form a star. ... In astronomy, starburst is a generic term to describe a region of space with a much higher than normal star formation. ... Relativistic Jet. ... For other uses, see Black hole (disambiguation). ... In astronomy, starburst is a generic term to describe a region of space with a much higher than normal star formation. ...


See also

The anisotropy of the star density in the night sky makes the galactic coordinate system very useful for coordinating surveys, both those which require high densities of stars (at low galactic latitudes) and those which require a low density of stars (at high galactic latitudes) Many galaxies, including the Milky... Sagittarius B2 (Sgr B2) is a giant molecular cloud of gas and dust that is located about 120 parsecs from the center of the Milky Way. ...

Further reading

  • Melia, Fulvio, The Black Hole in the Center of Our Galaxy, Princeton U Press, 2003
  • Eckart, A., Schödel, R., Straubmeier, C., The Black Hole at the Center of the Milky Way, Imperial College Press, London, 2005
  • Melia, Fulvio, The Galactic Supermassive Black Hole, Princeton U Press, 2007

This article does not cite its references or sources. ... This article does not cite its references or sources. ...

References

  1. ^ "SINFONI in the Galactic Center: young stars and IR flares in the central light month" . 

External links

The Astronomy Picture of the Day (or APOD) website is a service provided by NASA. According to the website, Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer. ... For other uses, see Milky Way (disambiguation). ... For other uses, see Universe (disambiguation). ... The Virgo Supercluster The Virgo Supercluster or Local Supercluster is the galactic supercluster that contains the Local Group, the latter which, in its turn, contains the Milky Way and Andromeda galaxies. ... A member of the Local Group of galaxies, irregular galaxy Sextans A is 4. ... Image File history File links Download high resolution version (1350x1350, 954 KB)Barred Spiral Milky Way Illustration Credit: R. Hurt (SSC), JPL-Caltech, NASA From http://apod. ... The Sagittarius Arm or Sagittarius-Carina Arm (labeled -I) is one of two major spiral arms of the Milky Way galaxy, along with the Cygnus Arm. ... The Scutum-Crux Arm or Centaurus Arm is a spiral arm of the Milky Way galaxy. ... Diagram of the Milky Ways spiral arms. ... The Perseus Arm (labeled +I) is a spiral arm of the Milky Way galaxy with a radius of 10. ... Observed structure of the Milky Ways spiral arms The Orion Arm or Local Arm (labeled 0) is a minor, spiral arm of the Milky Way galaxy. ... Category: ... A dwarf galaxy is a small galaxy composed of up to several billion stars, a small number compared to our own Milky Ways 200-400 billion stars. ... The Boötes Dwarf Galaxy (Boo dSph) is the faintest galaxy yet discovered, as of 2006, with a total luminosity of 100,000 Suns, and an absolute magnitude of -5. ... The Canes Venatici Dwarf Galaxy (CVn dSph) is the most distant satellite galaxy of the Milky Way as of 2006. ... The Canis Major Dwarf Galaxy located in the same part of the sky as the constellation of Canis Major. ... The Carina Dwarf is a dwarf galaxy in the Carina constellation. ... The Draco Dwarf galaxy was discovered by Albert G. Wilson of Lowell Observatory in 1954. ... The Fornax Dwarf is a dwarf galaxy in the constellation Fornax that was discovered in 1938 by Harlow Shapley. ... Leo I is a dwarf spheroidal galaxy in the constellation Leo. ... Leo II (or Leo B) is an dwarf spheroidal galaxy of the Local Group, in the constellation of Leo. ... The Phoenix Dwarf Galaxy is a dwarf galaxy and an irregular galaxy that was discovered in 1976 by Hans-Emil Schuster and Richard Martin West and mistaken for a globular cluster. ... The Sagittarius Dwarf Elliptical Galaxy (Sag DEG) is a satellite galaxy of the Milky Way Galaxy. ... The Sculptor Dwarf Galaxy (also called the Sculptor Dwarf Elliptical Galaxy or the Sculptor Dwarf Spheroidal Galaxy) is a dwarf spheroidal galaxy that is a satellite of the Milky Way. ... It has been suggested that this article or section be merged with Sextans A. (Discuss) The Sextans Dwarf Spheroidal is a dwarf spheroidal galaxy that was discovered in 1990 by Mike Irwin, M.T. Bridgeland, P.S. Bunclark and R.G. McMahon as the 8th satellite of the Milky Way... Ursa Major Dwarf is a dwarf spheroidal galaxy orbiting the Milky Way galaxy. ... The Ursa Minor Dwarf dwarf galaxy was discovered by A.G. Wilson of the Lowell Observatory in 1954. ... The Large Magellanic Cloud (LMC) is a nearby satellite galaxy of our own galaxy, the Milky Way. ... // Introduction Hierarchical Clustering tells us that galaxies are built up over time from collisions of smaller galaxies. ... Monoceros Ring is a proposed ring of stars around the Milky Way which consists of stars torn from the Canis Major Dwarf Galaxy as it merges with the Milky Way over the course of billions of years. ... The Small Magellanic Cloud (SMC) is a dwarf galaxy[1] in orbit around the Milky Way Galaxy. ... The Virgo Stellar Stream (or Virgo Overdensity) is the proposed name for a stream of stars in the constellation of Virgo which was discovered in 2005. ... Willman 1 or SDSS J1049+5103[2] is an extreme globular cluster or ultra low-mass dwarf galaxy discovered by a team lead by Beth Willman of New York University, using Sloan Digital Sky Survey data. ...

  Results from FactBites:
 
Galactic Center - Wikipedia, the free encyclopedia (336 words)
Work presented in 2002 by Antony Stark and Chris Martin mapping the gas density in a 400 light year region around the galactic center has revealed an accumulating ring with a mass several million times that of the Sun and near the critical density for star formation.
They predict that in approximately 200 million years there will be an episode of starburst in the galactic center, with many stars forming rapidly and undergoing supernovas at a hundred times the current rate.
The coordinates of Galactic Center in the Equatorial coordinate system are: RA 17h45m40.04s, Dec -29º 00' 28.1" (J2000 epoch).
Galactic center - definition of Galactic center in Encyclopedia (178 words)
Because of cool interstellar dust along the line of sight, the Galactic Center cannot be studied at visible, ultraviolet or soft X-ray wavelengths.
The complex radio source Sagittarius A appears to be located almost exactly at the Galactic Center, and contains an intense compact radio source, Sagittarius A*, which many astronomers believe may be a supermassive fl hole at the center of our galaxy.
The co-ordinates of Galactic Center in the Equatorial coordinate system are: Right Ascension 17h 45m 40s, Declination -29º 00' 28".
  More results at FactBites »

 
 

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