SGR 1806−20

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SGR 1806−20 is a magnetar, a type of neutron star with a very powerful magnetic field, that was discovered in 1979 and identified as a soft gamma repeater. SGR 1806−20 is located about 13 kiloparsecs (42,000 light-years)<ref name="ATNF"/> from Earth on the far side of the Milky Way in the constellation of Sagittarius. It has a diameter of no more than Template:Convert and rotates on its axis every 7.5 seconds (Template:Convert rotation speed at the equator on the surface). Template:As of, SGR 1806-20 is the most highly magnetized object ever observed, with a magnetic field of over 10¹⁵ gauss (G) (10¹¹ tesla) intensity<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> (compared to the Sun's 1–5 G and Earth's 0.25–0.65 G).

ExplosionEdit

File:SGR 1806-20 108530main cloudballPrint.jpg

Artist's impression of the surrounding cloud bubble

File:SGR 1806-20 108536main NeutronStar-Print1.jpg

Artist rendering of central neutron star

Forty-two 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).<ref name="top">{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref> In terms of gamma rays, the burst had an absolute magnitude of around −29.Template:Efn It was the brightest event known to have been sighted on this planet from an origin outside the Solar System until GRB 080319B. The magnetar released more energy in one-tenth of a second (1.0Template:E J) than the Sun releases in 150,000 years (4Template:E W × 4.8Template:E s = 1.85Template:E J).<ref name="top" /> Such a burst is thought to be the largest explosion observed in this galaxy by humans since the SN 1604, a supernova observed by Johannes Kepler in 1604. The gamma rays struck Earth's ionosphere and created more ionization, which briefly expanded the ionosphere. The quake was equivalent to a magnitude 32 on the Richter scale.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

A similar blast within 3 parsecs (10 light years) of Earth would severely affect the atmosphere,<ref name="top" /> by destroying the ozone layer and causing mass extinction,<ref name="Astronomy.com-Berman-2015">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="ScienceDaily-Blast Affected Earth-2005">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> and be similar in effect to a 12-kiloton nuclear blast at Template:Convert.Template:Citation needed The nearest known magnetar to Earth is 1E 1048.1-5937, located 9,000 light-years away in the constellation Carina.

LocationEdit

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 regions 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 LBV 1806-20, one of the brightest/most massive stars in the galaxy.

Planetary systemEdit

A 2024 paper posited that periodic gamma-ray and x-ray bursts from the pulsar are caused by a planet orbiting SGR 1806-20. This SGR 1806-20 b would be some kind of rocky world with a mass between 10-18 Earth masses with an orbital period of 398 days and a semi-major axis of 1.18 astronomical units. SGR 1806-20 b is notable for its eccentricity of 0.994, which would make it the most eccentric exoplanet known.<ref>https://exoplanet.eu/catalog/sgr_1806_20_b--10023/</ref><ref>Template:Cite journal</ref>