Posts Tagged ‘neutron star’

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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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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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.

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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.

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Cosmic Crashes Forging Gold

September 8, 2011 Leave a comment

Natural gold nuggets from California and Australia; Natural History Museum, London

Natural gold nuggets from California and Australia; Natural History Museum, London

The cosmic site where the heaviest chemical elements such as lead or gold are formed is likely to be identified: Ejected matter from neutron stars merging in a violent collision provides ideal conditions. In detailed numerical simulations, scientists of the Max Planck Institute for Astrophysics (MPA) and affiliated to the Excellence Cluster Universe and of the Free University of Brussels (ULB) have verified that the relevant reactions of atomic nuclei do take place in this environment, producing the heaviest elements in the correct abundances.

Most heavy chemical elements are formed in nuclear fusion reactions in stars. Also in the centre of our Sun, hydrogen is ”burned“ to create helium, thereby releasing energy. Heavier elements are then produced from helium if the star is more massive than our Sun. This process, however, only works up to iron; further fusion reactions do not yield any net energy gain. Therefore heavier elements cannot be produced in this fashion. Instead, they can be assembled when neutrons are captured onto ”seed“-nuclei, which then decay radioactively.

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