SGR 1806-20
Encyclopedia
|- style="vertical-align: top;"
| Distance
| 50,000 light-year
s (14.5 kiloparsecs)
SGR 1806-20 is a magnetar
, a particular type of neutron star
. It has been identified as a soft gamma repeater
. SGR 1806-20 is located about 14.5 kiloparsecs (50,000 light-year
s) from Earth
on the far side of our Milky Way
galaxy
in the constellation
of Sagittarius
. It has a diameter
of no more than 20 kilometres (12.4 mi) and rotates on its axis every 7.5 seconds (30,000 km/h rotation speed at the surface). , SGR 1806-20 is the most magnetized object ever perceived by humankind, with a magnetic field over 1015 gauss
(1011 teslas
) in intensity (compared to the Sun's 1-5 gauss). SGR 1806-20 has a magnetic field that is a quadrillion times stronger than that of the Earth.
. In terms of gamma rays the burst had an absolute magnitude around −29. It was the brightest event known to have been sighted on this planet from an origin outside our solar system. The gamma rays struck the ionosphere
and created more ionization which briefly expanded the ionosphere. The magnetar released more energy in one-tenth of a second (1.3×1039 J
) than our sun has released in 100,000 years (4×1026 W
× 3.2×1012 s = 1.3×1039 J). Such a burst is thought to be the largest explosion observed by humans in the galaxy since the SN 1604
supernova observed by Johannes Kepler
in 1604.
A similar blast within 3 parsecs (10 light years) of Earth would destroy the ozone layer and would be similar to a 12 kt of TNT (50 TJ) nuclear blast at 7.5 km. The nearest known magnetar to earth is 1E 1048.1-5937
, located 9,000 light-years away in the constellation Carina
.
s in the Milky Way. Cluster 1806-20 is made up of some highly unusual stars, including at least two carbon-rich Wolf-Rayet stars (WC9d and WCL), two blue hypergiants, and one of the brightest/most massive stars in the galaxy LBV 1806-20.
| Distance
Cosmic distance ladder
The cosmic distance ladder is the succession of methods by which astronomers determine the distances to celestial objects. A real direct distance measurement of an astronomical object is possible only for those objects that are "close enough" to Earth...
| 50,000 light-year
Light-year
A light-year, also light year or lightyear is a unit of length, equal to just under 10 trillion kilometres...
s (14.5 kiloparsecs)
SGR 1806-20 is a magnetar
Magnetar
A magnetar is a type of neutron star with an extremely powerful magnetic field, the decay of which powers the emission of copious high-energy electromagnetic radiation, particularly X-rays and gamma rays...
, a particular type of neutron star
Neutron star
A neutron star is a type of stellar remnant that can result from the gravitational collapse of a massive star during a Type II, Type Ib or Type Ic supernova event. Such stars are composed almost entirely of neutrons, which are subatomic particles without electrical charge and with a slightly larger...
. It has been identified as a soft gamma repeater
Soft gamma repeater
A soft gamma repeater is an astronomical object which emits large bursts of gamma-rays and X-rays at irregular intervals. It is conjectured that they are a type of magnetar or, alternatively, neutron stars with fossil disks around them....
. SGR 1806-20 is located about 14.5 kiloparsecs (50,000 light-year
Light-year
A light-year, also light year or lightyear is a unit of length, equal to just under 10 trillion kilometres...
s) from Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
on the far side of our 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...
galaxy
Galaxy
A galaxy is a massive, gravitationally bound system that consists of stars and stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component tentatively dubbed dark matter. The word galaxy is derived from the Greek galaxias , literally "milky", a...
in the constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....
of Sagittarius
Sagittarius (constellation)
Sagittarius is a constellation of the zodiac, the one containing the galactic center. Its name is Latin for the archer, and its symbol is , a stylized arrow. Sagittarius is commonly represented as a centaur drawing a bow...
. It has a diameter
Diameter
In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints are on the circle. The diameters are the longest chords of the circle...
of no more than 20 kilometres (12.4 mi) and rotates on its axis every 7.5 seconds (30,000 km/h rotation speed at the surface). , SGR 1806-20 is the most magnetized object ever perceived by humankind, with a magnetic field over 1015 gauss
Gauss (unit)
The gauss, abbreviated as G, is the cgs unit of measurement of a magnetic field B , named after the German mathematician and physicist Carl Friedrich Gauss. One gauss is defined as one maxwell per square centimeter; it equals 1 tesla...
(1011 teslas
Tesla (unit)
The tesla is the SI derived unit of magnetic field B . One tesla is equal to one weber per square meter, and it was defined in 1960 in honour of the inventor, physicist, and electrical engineer Nikola Tesla...
) in intensity (compared to the Sun's 1-5 gauss). SGR 1806-20 has a magnetic field that is a quadrillion times stronger than that of the Earth.
Explosion
On December 27, 2004, the radiation from an explosion on the surface of SGR 1806-20 reached EarthEarth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
. In terms of gamma rays the burst had an absolute magnitude around −29. It was the brightest event known to have been sighted on this planet from an origin outside our solar system. The gamma rays struck the ionosphere
Ionosphere
The ionosphere is a part of the upper atmosphere, comprising portions of the mesosphere, thermosphere and exosphere, distinguished because it is ionized by solar radiation. It plays an important part in atmospheric electricity and forms the inner edge of the magnetosphere...
and created more ionization which briefly expanded the ionosphere. The magnetar released more energy in one-tenth of a second (1.3×1039 J
Joule
The joule ; symbol J) is a derived unit of energy or work in the International System of Units. It is equal to the energy expended in applying a force of one newton through a distance of one metre , or in passing an electric current of one ampere through a resistance of one ohm for one second...
) than our sun has released in 100,000 years (4×1026 W
Watt
The watt is a derived unit of power in the International System of Units , named after the Scottish engineer James Watt . The unit, defined as one joule per second, measures the rate of energy conversion.-Definition:...
× 3.2×1012 s = 1.3×1039 J). Such a burst is thought to be the largest explosion observed by humans in the galaxy since the SN 1604
SN 1604
Supernova 1604, also known as Kepler's Supernova, Kepler's Nova or Kepler's Star, was a supernova that occurred in the Milky Way, in the constellation Ophiuchus. , it is the last supernova to have been unquestionably observed in our own galaxy, occurring no farther than 6 kiloparsecs or about...
supernova observed by Johannes Kepler
Johannes Kepler
Johannes Kepler was a German mathematician, astronomer and astrologer. A key figure in the 17th century scientific revolution, he is best known for his eponymous laws of planetary motion, codified by later astronomers, based on his works Astronomia nova, Harmonices Mundi, and Epitome of Copernican...
in 1604.
A similar blast within 3 parsecs (10 light years) of Earth would destroy the ozone layer and would be similar to a 12 kt of TNT (50 TJ) nuclear blast at 7.5 km. The nearest known magnetar to earth is 1E 1048.1-5937
AXP 1E 1048-59
Anomalous X-ray pulsar 1E 1048.1-5937 was the first AXP ever observed to emit an SGR-like X-ray burst....
, located 9,000 light-years away in the constellation Carina
Carina (constellation)
Carina is a constellation in the southern sky. Its name is Latin for the keel of a ship, and it was formerly part of the larger constellation of Argo Navis until that constellation was divided in three.-Stars:...
.
Location
SGR 1806-20 lies at the core of radio nebula G10.0-0.3 and is a component of cluster 1806-20, itself a component of W31, one of the largest H II regionH II region
An H II region is a large, low-density cloud of partially ionized gas in which star formation has recently taken place. The short-lived, blue stars forged in these regions emit copious amounts of ultraviolet light, ionizing the surrounding gas...
s in the Milky Way. Cluster 1806-20 is made up of some highly unusual stars, including at least two carbon-rich Wolf-Rayet stars (WC9d and WCL), two blue hypergiants, and one of the brightest/most massive stars in the galaxy LBV 1806-20.
See also
- Cl* 1806-20 -- star clusterStar clusterStar clusters or star clouds are groups of stars. Two types of star clusters can be distinguished: globular clusters are tight groups of hundreds of thousands of very old stars which are gravitationally bound, while open clusters, more loosely clustered groups of stars, generally contain less than...
- LBV 1806-20 -- luminous blue variableLuminous blue variableLuminous blue variables, also known as S Doradus variables, are very bright, blue, hypergiant variable stars named after S Doradus, the brightest star of the Large Magellanic Cloud. They exhibit long, slow changes in brightness, punctuated by occasional outbursts in brightness during substantial...
- Soft gamma repeaterSoft gamma repeaterA soft gamma repeater is an astronomical object which emits large bursts of gamma-rays and X-rays at irregular intervals. It is conjectured that they are a type of magnetar or, alternatively, neutron stars with fossil disks around them....
- Bryan GaenslerBryan GaenslerBryan Malcolm Gaensler is an Australian astronomer and former Young Australian of the Year, currently based at the University of Sydney. He is best known for his work on magnetars, supernova remnants and magnetic fields.- Education :...
External links
- An exceptionally bright flare from SGR 1806–20 and the origins of short-duration big gamma-ray bursts, 2005-04-28 (NatureNature (journal)Nature, first published on 4 November 1869, is ranked the world's most cited interdisciplinary scientific journal by the Science Edition of the 2010 Journal Citation Reports...
) - Huge 'star-quake' rocks Milky Way, 2005-02-18, (BBC News OnlineBBC News OnlineBBC News Online is the website of BBC News, the division of the BBC responsible for newsgathering and production. The website is the most popular news website in the United Kingdom and forms a major part of BBC Online ....
) - Brightest galactic flash ever detected hits Earth 2005-02-18 (space.comSpace.comSpace.com is a space and astronomy news website. Its stories are often syndicated to other media outlets, including CNN, MSNBC, Yahoo!, and USA Today.Space.com was founded by former CNN anchor Lou Dobbs and Rich Zahradnik, in July 1999...
) - http://www.theage.com.au/articles/2005/02/19/1108709484471.html?from=top5 2005-02-20 (The AgeThe AgeThe Age is a daily broadsheet newspaper, which has been published in Melbourne, Australia since 1854. Owned and published by Fairfax Media, The Age primarily serves Victoria, but is also available for purchase in Tasmania, the Australian Capital Territory and border regions of South Australia and...
) Registration required. - Huge quake cracks star 2005-09-27 (space.com)
- NASA Sees Hidden Structure Of Neutron Star In Starquake (SpaceDaily) April 26, 2006