SGR 1806−20 is a

magnetar A magnetar is a type of neutron star with an extremely powerful magnetic field (∼109 to 1011 T, ∼1013 to 1015 G). The magnetic-field decay powers the emission of high-energy electromagnetic radiation, particularly X-rays and gamma rays.War ...

, a type of

neutron star A neutron star is the collapsed core of a massive supergiant star, which had a total mass of between 10 and 25 solar masses, possibly more if the star was especially metal-rich. Except for black holes and some hypothetical objects (e.g. w ...

with a very powerful magnetic field, that was discovered in 1979 and identified as a

soft gamma repeater A soft gamma repeater (SGR) 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. Hi ...

. SGR 1806−20 is located about 13

kiloparsec The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equal to or (au), i.e. . The parsec unit is obtained by the use of parallax and trigonometry, and ...

s (42,000 light-years) from Earth on the far side of the

Milky Way The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye. ...

in the constellation of Sagittarius. It has a

diameter In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints lie on the circle. It can also be defined as the longest chord of the circle. Both definitions are also valid fo ...

of no more than and rotates on its axis every 7.5 seconds ( rotation speed at the surface). , SGR 1806-20 is the most highly magnetized object ever observed, with a magnetic field over 10¹⁵

gauss Johann Carl Friedrich Gauss (; german: Gauß ; la, Carolus Fridericus Gauss; 30 April 177723 February 1855) was a German mathematician and physicist who made significant contributions to many fields in mathematics and science. Sometimes refer ...

(G) (10¹¹ tesla) in intensity (compared to the Sun's 1–5 G and Earth's 0.25–0.65 G).

Explosion

SGR 1806-20 108536main NeutronStar-Print1

Fifty thousand years after a starquake occurred on the surface of SGR 1806-20, the radiation from the resultant explosion reached Earth on December 27, 2004 ( GRB 041227). 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 the

Solar System The Solar System Capitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar ...

, until the

GRB 080319B __NOTOC__ GRB 080319B was a gamma-ray burst (GRB) detected by the Swift satellite at 06:12 UTC on March 19, 2008. The burst set a new record for the farthest object that was observable with the naked eye: it had a peak visual apparent magnitude ...

. The magnetar released more energy in one-tenth of a second (1.0 J) than the Sun releases in 150,000 years (4 W × 4.8 s = 1.85 J).NASA.gov
NASA - Cosmic Explosion Among the Brightest in Recorded History Such a burst is thought to be the largest explosion observed in this galaxy by humans since the

SN 1604 SN 1604, also known as Kepler's Supernova, Kepler's Nova or Kepler's Star, was a Type Ia supernova that occurred in the Milky Way, in the constellation Ophiuchus. Appearing in 1604, it is the most recent supernova in the Milky Way galaxy to hav ...

supernova observed by Johannes Kepler in 1604. The gamma rays struck Earth's ionosphere and created more ionization, which briefly expanded the ionosphere. A similar blast within 3 parsecs (10 light years) of Earth would severely affect the atmosphere, by destroying the ozone layer and causing mass extinction, and be similar in effect to a 12-

kiloton TNT equivalent is a convention for expressing energy, typically used to describe the energy released in an explosion. The is a unit of energy defined by that convention to be , which is the approximate energy released in the detonation of a ...

nuclear blast at . The nearest known magnetar to Earth is 1E 1048.1-5937, located 9,000 light-years away in the constellation

Carina Carina may refer to: Places Australia * Carina, Queensland, a suburb in Brisbane * Carina Heights, Queensland, a suburb in Brisbane * Carina, Victoria, a locality in Mildura Serbia * Carina, Osečina, a village in the Kolubara District ...

Location

SGR 1806−20 lies at the core of radio nebula G10.0-0.3 and is a member of an open cluster named after it, itself a component of W31, one of the largest

H II region An H II region or HII region is a region of interstellar atomic hydrogen that is ionized. It is typically in a molecular cloud of partially ionized gas in which star formation has recently taken place, with a size ranging from one to hundreds ...

s in the Milky Way. Cluster 1806-20 is made up of some highly unusual stars, including at least two carbon-rich

Wolf–Rayet star Wolf–Rayet stars, often abbreviated as WR stars, are a rare heterogeneous set of stars with unusual spectra showing prominent broad emission lines of ionised helium and highly ionised nitrogen or carbon. The spectra indicate very high surface ...

s (WC9d and WCL), two blue hypergiants, and

LBV 1806-20 LBV may refer to: * Late bottled vintage, a type of Port wine * Luminous blue variable, a very bright, blue, hypergiant variable star * Libreville International Airport (IATA: LBV), in Libreville, Gabon * Load bearing vest, an individual integrate ...

, one of the brightest/most massive stars in the galaxy.

Notes

References

External links

Anniversary of a Cosmic Blast
(

Phil Plait Philip Cary Plait (born September 30, 1964), also known as The Bad Astronomer, is an American astronomer, skeptic, and popular science blogger. Plait has worked as part of the Hubble Space Telescope team, images and spectra of astronomical objec ...

Dec. 27, 2012)
An exceptionally bright flare from SGR 1806-20 and the origins of short-duration big gamma-ray bursts
2005-04-28 (''

Nature Nature, in the broadest sense, is the physical world or universe. "Nature" can refer to the phenomena of the physical world, and also to life in general. The study of nature is a large, if not the only, part of science. Although humans are ...

'')
Huge 'star-quake' rocks Milky Way
2005-02-18, (

BBC News Online BBC News Online is the website of BBC News, the division of the BBC responsible for newsgathering and production. It is one of the most popular news websites, with 1.2 billion website visits in April 2021, as well as being used by 60% of the U ...

)
Brightest galactic flash ever detected hits Earth
2005-02-18 (

space.com Space.com is an online publication focused on space exploration, astronomy, skywatching and entertainment, with editorial teams based in the United States and United Kingdom. The website offers live coverage of space missions, astronomical discov ...

)

2005-02-20 (''

The Age ''The Age'' is a daily newspaper in Melbourne, Australia, that has been published since 1854. Owned and published by Nine Entertainment, ''The Age'' primarily serves Victoria, but copies also sell in Tasmania, the Australian Capital Territory ...

'') Registration required.
Huge quake cracks star
2005-09-27 (space.com)

(''SpaceDaily'') April 26, 2006 {{DEFAULTSORT:SGR 1806-20 Soft gamma repeaters Sagittarius (constellation) Astronomical objects discovered in 1979 Magnetars

Explosion

Location

See also

Notes

References

External links