The active life of a magnetar is short compared to other celestial bodies. A magnetar's magnetic field gives rise to very strong and characteristic bursts of X-rays and gamma rays. Most observed magnetars rotate once every two to ten seconds, whereas typical neutron stars, observed as radio pulsars, rotate one to ten times per second. Magnetars are differentiated from other neutron stars by having even stronger magnetic fields, and by rotating more slowly in comparison. The density of the interior of a magnetar is such that a tablespoon of its substance would have a mass of over 100 million tons. They are formed by the collapse of a star with a mass 10–25 times that of the Sun. Like other neutron stars, magnetars are around 20 kilometres (12 mi) in diameter, and have a mass of about 1.4 solar masses.
It has been suggested that magnetars are the source of fast radio bursts (FRB), in particular as a result of findings in 2020 by scientists using the Australian Square Kilometre Array Pathfinder (ASKAP) radio telescope. As of July 2021, 24 confirmed magnetars were known. Over the following decade, the magnetar hypothesis became widely accepted, and was extended to explain anomalous X-ray pulsars (AXPs).
Their proposal sought to explain the properties of transient sources of gamma rays, now known as soft gamma repeaters (SGRs). The existence of magnetars was proposed in 1992 by Robert Duncan and Christopher Thompson.
The magnetic-field decay powers the emission of high- energy electromagnetic radiation, particularly X-rays and gamma rays. Artist's conception of a powerful magnetar in a star clusterĪ magnetar is a type of neutron star with an extremely powerful magnetic field (∼10 9 to 10 11 T, ∼10 13 to 10 15 G).
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