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SGR 1745-2900: Magnetar Near Supermassive Black Hole Delivers Surprises


Credit: NASA/CXC/INAF/F.Coti Zelati et al

Credit: NASA/CXC/INAF/F.Coti Zelati et al

In 2013, astronomers announced they had discovered a magnetar exceptionally close to the supermassive black hole at the center of the Milky Way using a suite of space-borne telescopes including NASA’s Chandra X-ray Observatory.

Magnetars are dense, collapsed stars (called “neutron stars”) that possess enormously powerful magnetic fields. At a distance that could be as small as 0.3 light years (or about 2 trillion miles) from the 4-million-solar mass black hole in the center of our Milky Way galaxy, the magnetar is by far the closest neutron star to a supermassive black hole ever discovered and is likely in its gravitational grip.

A new study uses long-term monitoring observations to reveal that the amount of X-rays from SGR 1745-2900 is dropping more slowly than other previously observed magnetars, and its surface is hotter than expected.

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NASA’s Fermi Satellite Finds Hints Of Starquakes In Magnetar ‘Storm’

October 24, 2014 Leave a comment

Image Credit: NASA's Goddard Space Flight Center/S. Wiessinger

Image Credit: NASA’s Goddard Space Flight Center/S. Wiessinger

NASA’s Fermi Gamma-ray Space Telescope detected a rapid-fire “storm” of high-energy blasts from a highly magnetized neutron star, also called a magnetar, on Jan. 22, 2009. Now astronomers analyzing this data have discovered underlying signals related to seismic waves rippling throughout the magnetar.

Such signals were first identified during the fadeout of rare giant flares produced by magnetars. Over the past 40 years, giant flares have been observed just three times — in 1979, 1998 and 2004 — and signals related to starquakes, which set the neutron stars ringing like a bell, were identified only in the two most recent events.

“Fermi’s Gamma-ray Burst Monitor (GBM) has captured the same evidence from smaller and much more frequent eruptions called bursts, opening up the potential for a wealth of new data to help us understand how neutron stars are put together,” said Anna Watts, an astrophysicist at the University of Amsterdam in the Netherlands and co-author of a new study about the burst storm. “It turns out that Fermi’s GBM is the perfect tool for this work.”

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Magnetar Formation Mystery Solved?


 Artist’s impression of the magnetar in the star cluster Westerlund 1. Credit: ESO/L. Calçada


Artist’s impression of the magnetar in the star cluster Westerlund 1. Credit: ESO/L. Calçada

Magnetars are the bizarre super-dense remnants of supernova explosions. They are the strongest magnets known in the Universe — millions of times more powerful than the strongest magnets on Earth.

When a massive star collapses under its own gravity during a supernova explosion it forms either a neutron star or black hole. Magnetars are an unusual and very exotic form of neutron star. Like all of these strange objects they are tiny and extraordinarily dense — a teaspoon of neutron star material would have a mass of about a billion tonnes — but they also have extremely powerful magnetic fields. Magnetar surfaces release vast quantities of gamma rays when they undergo a sudden adjustment known as a starquake as a result of the huge stresses in their crusts.

The Westerlund 1 star cluster, located 16 000 light-years away in the southern constellation of Ara (the Altar), hosts one of the two dozen magnetars known in the Milky Way.

“In our earlier work (eso1034) we showed that the magnetar in the cluster Westerlund 1 (eso0510) must have been born in the explosive death of a star about 40 times as massive as the Sun. But this presents its own problem, since stars this massive are expected to collapse to form black holes after their deaths, not neutron stars. We did not understand how it could have become a magnetar,” says Simon Clark, lead author of the paper reporting these results.

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With A Deadly Embrace, ‘Spidery’ Pulsars Consume Their Mates

February 24, 2014 Leave a comment

Artist's concept. Image Credit: NASA's Goddard Space Flight Center

Artist’s concept. Image Credit: NASA’s Goddard Space Flight Center

Black widow spiders and their Australian cousins, known as redbacks, are notorious for their tainted love, expressed as an unsettling tendency to kill and devour their male partners. Astronomers have noted similar behavior among two rare breeds of binary system that contain rapidly spinning neutron stars, also known as pulsars.

“The essential features of black widow and redback binaries are that they place a normal but very low-mass star in close proximity to a millisecond pulsar, which has disastrous consequences for the star,” said Roger Romani, a member of the Kavli Institute for Particle Astrophysics and Cosmology, an institute run jointly by Stanford and SLAC National Accelerator Laboratory in Menlo Park, Calif. Black widow systems contain stars that are both physically smaller and of much lower mass than those found in redbacks.

So far, astronomers have found at least 18 black widows and nine redbacks within the Milky Way, and additional members of each class have been discovered within the dense globular star clusters that orbit our galaxy.

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NASA’s Chandra Sees Runaway Pulsar Firing An Extraordinary Jet

February 19, 2014 2 comments

Image Credit: X-ray: NASA/CXC/ISDC/L.Pavan et al, Radio: CSIRO/ATNF/ATCA O

Image Credit: X-ray: NASA/CXC/ISDC/L.Pavan et al, Radio: CSIRO/ATNF/ATCA O

NASA’s Chandra X-ray Observatory has seen a fast-moving pulsar escaping from a supernova remnant while spewing out a record-breaking jet – the longest of any object in the Milky Way galaxy — of high-energy particles.

The pulsar, a type of neutron star, is known as IGR J11014-6103. IGR J11014-6103’s peculiar behavior can likely be traced back to its birth in the collapse and subsequent explosion of a massive star.

Originally discovered with the European Space Agency satellite INTEGRAL, the pulsar is located about 60 light-years away from the center of the supernova remnant SNR MSH 11-61A in the constellation of Carina. Its implied speed is between 2.5 million and 5 million mph, making it one of the fastest pulsars ever observed.

“We’ve never seen an object that moves this fast and also produces a jet,” said Lucia Pavan of the University of Geneva in Switzerland and lead author of a paper published Tuesday,in the journal Astronomy and Astrophysics. “By comparison, this jet is almost 10 times longer than the distance between the sun and our nearest star.”

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Powerful Ancient Explosions Explain New Class Of Supernovae

December 18, 2013 Leave a comment

From the Supernova Legacy Survey

From the Supernova Legacy Survey

Astronomers affiliated with the Supernova Legacy Survey (SNLS) have discovered two of the brightest and most distant supernovae ever recorded, 10 billion light-years away and a hundred times more luminous than a normal supernova. Their findings appear in the Dec. 20 issue of the Astrophysical Journal.

These newly discovered supernovae are especially puzzling because the mechanism that powers most of them — the collapse of a giant star to a black hole or normal neutron star — cannot explain their extreme luminosity. Discovered in 2006 and 2007, the supernovae were so unusual that astronomers initially could not figure out what they were or even determine their distances from Earth.

“At first, we had no idea what these things were, even whether they were supernovae or whether they were in our galaxy or a distant one,” said lead author D. Andrew Howell, a staff scientist at Las Cumbres Observatory Global Telescope Network (LCOGT) and adjunct faculty at UC Santa Barbara. “I showed the observations at a conference, and everyone was baffled. Nobody guessed they were distant supernovae because it would have made the energies mind-bogglingly large. We thought it was impossible.”

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Fledgling Supernova Remnant Reveals Neutron Star’s Secrets

December 6, 2013 1 comment

Image: X-ray: NASA/CXC/UW-Madison/S. Heinz et al; Optical: DSS; Radio: CSIRO/ATNF/ATCA

Image: X-ray: NASA/CXC/UW-Madison/S. Heinz et al; Optical: DSS; Radio: CSIRO/ATNF/ATCA

With the help of NASA’s Chandra X-ray Observatory and the Australia Telescope Compact Array, an international team of astronomers has identified the glowing wreck of a star that exploded a mere 2,500 years ago — the blink of an eye in astronomical terms.

The observations, made by a team led by UW-Madison astronomy professor Sebastian Heinz, reveal an astrophysical novelty of the Milky Way: a glowing nebula created when the star exploded and, inside of it, the collapsed core of the exploded star, a neutron star, still clinging to its former companion star. It is the only known example of such a system in our galaxy.

The new observations are reported Dec. 3 in the Astrophysical Journal and are important because they provide a unique laboratory to test key theories of stellar evolution, especially about the stage of a star’s life just after most of it has been obliterated in a supernova explosion.

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Magnetic Star Reveals Its Hidden Power

August 14, 2013 Leave a comment

Artist's impression. Credit: ESA/ATG Medialab

Artist’s impression. Credit: ESA/ATG Medialab

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.

Full Story: http://www.ucl.ac.uk/maps-faculty/maps-news-publication/maps1323
Also: http://www.esa.int/Our_Activities/Space_Science/Mysterious_magnetar_boasts_one_of_strongest_magnetic_fields_in_Universe

The Largest Magnetic Fields In The Universe


An ultra-dense (“hypermassive”) neutron star is formed when two neutron stars in a binary system finally merge. Its short life ends with the catastrophic collapse to a black hole, possibly powering a short gamma-ray burst, one of the brightest explosions observed in the universe. Short gamma-ray bursts as observed with satellites like XMM Newton, Fermi or Swift release within a second the same amount of energy as our Galaxy in one year. It has been speculated for a long time that enormous magnetic field strengths, possibly higher than what has been observed in any known astrophysical system, are a key ingredient in explaining such emission. Scientists at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute/AEI) have now succeeded in simulating a mechanism which could produce such strong magnetic fields (stronger than ten or hundred million billion times the Earth’s magnetic field)* prior to the collapse to a black hole.

* Strength inserted from elsewhere in the story.

Full Story: http://www.aei.mpg.de/303590/Die_staerksten_Magnetfelder_im_Universum

Earth’s Gold Came From Colliding Dead Stars


Artist's conception. Credit: Dana Berry, SkyWorks Digital, Inc.

Artist’s conception. Credit: Dana Berry, SkyWorks Digital, Inc.

We value gold for many reasons: its beauty, its usefulness as jewelry, and its rarity. Gold is rare on Earth in part because it’s also rare in the universe. Unlike elements like carbon or iron, it cannot be created within a star. Instead, it must be born in a more cataclysmic event – like one that occurred last month known as a short gamma-ray burst (GRB). Observations of this GRB provide evidence that it resulted from the collision of two neutron stars – the dead cores of stars that previously exploded as supernovae. Moreover, a unique glow that persisted for days at the GRB location potentially signifies the creation of substantial amounts of heavy elements – including gold.

“We estimate that the amount of gold produced and ejected during the merger of the two neutron stars may be as large as 10 moon masses – quite a lot of bling!” says lead author Edo Berger of the Harvard-Smithsonian Center for Astrophysics (CfA).

Full Story: http://www.cfa.harvard.edu/news/2013/pr201319.html