SGR 1806-20

From Freepedia

In astronomy, 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 500 exametres (50,000 light-years) 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 miles) and rotates on its axis every 7.5 seconds. The corresponding supernova remnant is the radio nebula G10.0-0.3.

Image:SGR 1806-20 positon.jpg

On December 27, 2004, the radiation from an explosion on the surface of SGR 1806-20 reached Earth. In terms of gamma rays the burst was brighter than a full moon and had an absolute magnitude of around −29¹. It was the brightest event known to have impacted 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 100 petametres (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. Fortunately, the nearest known magnetar to earth is 1E 2259+586, 120 exametres (13,000 light years) away.