Mysterious magnetar boasts one of strongest magnetic fields in Universe

A team of astronomers including two researchers from UCL’s Mullard Space Science Laboratory has made the first ever measurement of the magnetic field at a specific spot on the surface of a magnetar. Magnetars are a type of neutron star,…

A team of astronomers including two researchers from UCL’s Mullard Space Science Laboratory has made the first ever measurement of the magnetic field at a specific spot on the surface of a magnetar. Magnetars are a type of neutron star, the dense and compact core of a giant star which has blasted away its outer layers in a supernova explosion.

Magnetars have among the strongest magnetic fields in the Universe. Until now, only their large scale magnetic field had been measured. However, using a new technique and observations of a magnetar in X-rays, the astronomers have now revealed a strong, localised surface magnetic field on one.
Magnetars are very puzzling neutron stars. Astronomers discovered them through their unusual behaviour when observed in X-ray wavelengths, including sudden outbursts of radiation and occasional giant flares. These peculiar features of magnetars are caused by the evolution, dissipation and decay of their super-strong magnetic fields, which are hundreds or thousands of times more intense than those of the more common type of neutron stars, the radio pulsars.
The magnetic field of a magnetar can have a complex structure. The most obvious, and easy-to-measure, component is the large scale external magnetic field, which is shaped (and behaves) much like a regular bar magnet’s. This is known as the dipolar field.
The study was carried out on a magnetar called SGR 0418+5729. A few years ago, this star was discovered to have a relatively gentle dipolar magnetic field compared to other magnetars. However, the star was showing the typical flaring and bursting activities seen in other magnetars, leading scientists to suggest that the star’s magnetic activity might be caused by a field hidden beneath its surface.

Sometimes, the surface breaks and the hidden magnetic field leaks out (artist’s impression) Credit: ESA/ATG Medialab
This new study, based on observations from ESA’s XMM-Newton X-ray space telescope, has finally found evidence that SGR 0418+5729 is indeed concealing a very strong magnetic field in its interior.
“This magnetar has a strong magnetic field inside it, but it is hidden beneath the surface. The only way you can detect that is to find a flaw on the surface, where the concealed magnetic field can leak out,” says Silvia Zane (UCL Mullard Space Science Laboratory), one of the co-authors of the study.

Such magnetic leaks would also explain the outbursts and flares of radiation observed from magnetars. The warped magnetic field trapped inside the star builds up stress below the magnetar’s surface, occasionally breaking its ‘crust’ apart and releasing sudden flashes of X-rays.
Magnetars are far too small – only around 20km across – and distant for even the best telescopes to see any details on their surfaces. They appear just as dots of light in astronomers’ observations. So the team had to look for indirect signs of variation on SGR 0418+5729’s surface. To do this, they measured how the magnetar’s X-ray emissions varied as the star rotates.
“SGR 0418+5729 rotates once every 9 seconds. We found that at one point during the rotation, the magnetar’s X-ray brightness drops sharply. That means something on or near one part of the surface is absorbing the radiation,” adds Roberto Turolla (an honorary professor at MSSL and co-author of the study).

Closeup of the magnetic field leaking out of a magnetar (artist’s impression) Credit: ESA/ATG Medialab
The team believes that a concentration of protons over a small area of the magentar’s surface – perhaps as little as a few hundred metres across – is absorbing the X-rays. The protons are confined to a small volume near the surface by a strong, localised magnetic field emerging from the magnetar’s interior, giving powerful evidence that a strong and twisted internal magnetic field lurks beneath the surface.
“This exciting discovery also confirms that, in principle, other pulsars with relatively low external magnetic fields might conceal a similar strong magnetic field in the interior. As a result, many pulsars may switch on and become active flaring magnetars for a while, so in the future we may discover much more magnetars than what we previously thought. This call for a major revision of our current ideas of magnetic field formation and amplification in neutron stars,” explains Zane.
The study is published in the journal Nature.

Explore further:

A hidden population of exotic neutron stars

More information: “A variable absorption feature in the X-ray spectrum of a magnetar,” by A. Tiengo et al is published in Nature, 15 August 2013.

Journal reference:


Provided by

University College London

view popular

4.7 /5 (29 votes)

Related Stories

A hidden population of exotic neutron stars

May 23, 2013

( —Magnetars – the dense remains of dead stars that erupt sporadically with bursts of high-energy radiation – are some of the most extreme objects known in the Universe. A major campaign using …

A magnetic monster’s dual personality

Jul 16, 2012

( — Is it a magnetar or is it a pulsar? A second member of a rare breed of dead, spinning star has been identified thanks to an armada of space-based X-ray telescopes, including ESA’s XMM-Newton. …

Mysterious pulsar with hidden powers discovered

Oct 14, 2010

Dramatic flares and bursts of energy – activity previously thought reserved for only the strongest magnetized pulsars – has been observed emanating from a weakly magnetised, slowly rotating pulsar. The international …

Giant eruption reveals ‘dead’ star

Jun 16, 2009

An enormous eruption has found its way to Earth after travelling for many thousands of years across space. Studying this blast with ESA’s XMM-Newton and Integral space observatories, astronomers have discovered a dead star …

A strong magnetic field around the Milky Way’s black hole

4 hours ago

( —Astronomers have made an important measurement of the magnetic field emanating from a swirling disk of material surrounding the black hole at the center of our Milky Way Galaxy. The measurement, …

Cosmic glitch: Super-dense star is first ever found suddenly slowing its spin

May 29, 2013

One of the densest objects in the universe, a neutron star about 10,000 light years from Earth, has been discovered suddenly putting the brakes on its spinning speed. The event is a mystery that holds important …

Recommended for you

Pulsars make a GPS for the cosmos

7 hours ago

( —CSIRO scientists have written software that could guide spacecraft to Alpha Centauri, show that the planet Nibiru doesn’t exist … and prove that the Earth goes around the Sun.

First MeerKAT antenna foundation poured

8 hours ago

The concrete for the first MeerKAT antenna foundation was poured yesterday at South Africa’s SKA site in the Karoo. This is the first of 64 similar foundations that will be constructed for this telescope …

Revealing dark energy’s hold on the Universe: What a new collaboration hopes to uncover

11 hours ago

The race is on to solve the mystery of dark energy, the unknown force that is causing the universe to expand faster and faster. It’s one of the biggest open questions in cosmology, but now a handful of high-profile projects …

NASA gives up fixing Kepler planet-hunting telescope

Aug 15, 2013

NASA called off all attempts to fix its crippled Kepler space telescope Thursday. But it’s not quite ready to call it quits on the remarkable, robotic planet hunter.

Cosmic turbulences result in star and black hole formation

Aug 15, 2013

Just how stars and black holes in the Universe are able to form from rotating matter is one of the big questions of astrophysics. What we do know is that magnetic fields figure prominently into the picture. …

Astronomers show galaxies had ‘mature’ shapes 11.5 billion years ago

Aug 15, 2013

Studying the evolution and anatomy of galaxies using the Hubble Space Telescope, an international team of astronomers led by doctoral candidate BoMee Lee and her advisor Mauro Giavalisco at the University …

User comments : 34

Adjust slider to filter visible comments by rank

Display comments: newest first

More news stories

Pulsars make a GPS for the cosmos

( —CSIRO scientists have written software that could guide spacecraft to Alpha Centauri, show that the planet Nibiru doesn’t exist … and prove that the Earth goes around the Sun.

Global Pliocene cooling digs deep canyons into the Andean Plateau

Incision of canyons into mountains is often interpreted by geoscientists as a proxy for surface uplift of the surroundings by geodynamic and tectonic processes. However, another possible cause for incision …

Dissolving brittle stars hint at implications of ocean acidification

( —Under the sea ice of Explorers Cove, Antarctica, is a startling array of life. Brittle stars, sea urchins and scallops grow in profusion on the seafloor, a stark contrast to the icy moonscape …

Two Russian cosmonauts turn cable guys in spacewalk

Russian cosmonauts are taking a spacewalk to lay cable for a new lab that’s due to arrive at the International Space Station in a few months.

Humble plants may save the planet

Marine ecologists call them seagrass meadows. They once wrapped Australia’s coastline providing sanctuary and food for dugongs and turtles, habitats for fish to breed and myriad other ecosystem services such …

Severe hypoglycemia in diabetes tied to cardiac disease

(HealthDay)—For patients with type 1 and type 2 diabetes, severe hypoglycemia is associated with severe hypertension, hypokalemia, and QT prolongation, according to a study published online Aug. 12 in Diabetes Ca …

Breath and butter: Resolving cholesterol’s role in human lung surfactants

(Medical Xpress)—Pulmonary surfactants are phospholipoproteins (surface-active lipoprotein complexes) that reduces alveolar surface tension through an air-water hydrophilic/hydrophobic interface. Pulmonary, …

‘Listening’ to black holes form with gravity waves

New technology that breaks the quantum measurement barrier has been developed to detect the gravity waves first predicted by Einstein in 1916.

New research suggests perovskite as cheaper replacement for silicon-based solar panels

( —Researchers at Oxford Photovoltaics and other companies investigating the use of perovskite—a crystalline organometal—as a replacement for silicon in photovoltaic cells have created prototypes …

Microsoft India team develop secure Peer-to-Peer acoustic NFC system

( —A team of researchers at Microsoft India has developed an alternative to standard NFC communications between hand-held devices—a software only system that makes use of the speaker and microphone …