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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 (or dissipation) powers the emission of high-energy electromagnetic radiation, particularly X-rays and gamma rays. The existence of magnetars was proposed in 1992 by Robert Duncan and Christopher Thompson, who sought to explain the properties of transient sources of gamma rays, now known as soft gamma repeaters (SGRs). Over the following decade, the magnetar hypothesis became widely accepted, and was extended to explain anomalous X-ray pulsars (AXPs). Out of approximately 3,000 neutron stars, there are 31 confirmed magnetars of which five are both magnetars and pulsars, as of January 2021. 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.

Like other neutron stars, magnetars are around 20 kilometres (12 mi) in diameter, and have a mass of about 1.4 solar masses. Magnetars are distinguished from other neutron stars by having even stronger magnetic fields and rotating more slowly. 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. A magnetar's magnetic field gives rise to very strong and characteristic bursts of X-rays and gamma rays. Their strong magnetic fields decay after about 10,000 years, after which activity and strong X-ray emission cease. Starquakes triggered on the surface of the magnetar disturb the magnetic field that encompasses it, often leading to extremely powerful gamma-ray flare emissions which have been recorded on Earth in 1979, 1998, and 2004.

Magnetars are characterized by their extremely powerful magnetic fields of ~109 to 1011 T. These magnetic fields are a hundred million times stronger than any man-made magnet, and about a trillion times more powerful than the field surrounding Earth. The magnetic field of a magnetar would be lethal even at a distance of 1,000 km due to the strong magnetic field distorting the electron clouds of the subject's constituent atoms, rendering the chemistry of sustaining life impossible. At a distance of halfway from Earth to the Moon, an average distance between the Earth and the Moon being 384,400 km (238,900 miles), a magnetar could wipe information from the magnetic stripes of all credit cards on Earth. As described in the February 2003 Scientific American cover story, remarkable things happen within a magnetic field of magnetar strength.

It is estimated that about one in ten supernova explosions results in a magnetar rather than a more standard neutron star or pulsar.

On February 21, 2008, it was announced that NASA and researchers at McGill University had discovered a neutron star with the properties of a radio pulsar that emitted some magnetically powered bursts, like a magnetar. Astronomers from Europe and China discovered this magnetar, named 3XMM J185246.6+003317, in 2013 by looking at images that had been taken in 2008 and 2009. In April 2020, a possible link between fast radio bursts (FRBs) and magnetars was suggested, based on observations of SGR 1935+2154, a likely magnetar located in the Milky Way galaxy.

On May 29, 2008, NASA's Spitzer Space Telescope discovered a ring of matter around this magnetar. The original star, from which the magnetar formed, had a mass 30 to 40 times that of the Sun. As of September 2008, ESO reports identification of an object which it has initially identified as a magnetar, SWIFT J195509+261406, originally identified by a gamma-ray burst (GRB 070610). This magnetar, contrary to predictions, has a low external magnetic field, and it might be as young as half a million years.

McGill Online Magnetar Catalog McGill Online Magnetar Catalog -- Main Table

Quick Facts

• Out of approximately 3,000 neutron stars, there are 31 confirmed magnetars of which five are both magnetars and pulsars, as of January 2021.
• Over the following decade, the magnetar hypothesis became widely accepted, and was extended to explain anomalous X-ray pulsars (AXPs).
• 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.
• McGill Online Magnetar Catalog McGill Online Magnetar Catalog -- Main Table
• Starquakes triggered on the surface of the magnetar disturb the magnetic field that encompasses it, often leading to extremely powerful gamma-ray flare emissions which have been recorded on Earth in 1979, 1998, and 2004.

Source material: Wikipedia - "Magnetar". Adapted and summarized for DiscoverScroll. Original contributors are credited through the linked Wikipedia article. Read original on Wikipedia. CC BY-SA 4.0. Changes were made from the original.