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Artists impression of a magnetar.  Credits: © 2008 Sky & Telescope: Gregg Dinderman

New Insights on Magnetars

14 Nov , 2008

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Neutron stars are leftovers of massive stars (10-50 times as massive as our Sun) that have collapsed under their own weight. Most are only about 20 km in diameter, but they are so compact that a teaspoon of neutron star stuff would weigh about one hundred million tons. Two other physical properties characterize a neutron star: their fast rotation and strong magnetic field. Magnetars form a class of neutron stars with ultra-strong magnetic fields, approximately a thousand times stronger than that of ordinary neutron stars, making them the strongest known magnets in the cosmos. But astronomers have been unsure exactly why magnetars shine in X-rays. Data from ESA’s XMM-Newton and Integral orbiting observatories are being used to test, for the first time, the X-ray properties of magnetars.

So far, about 15 magnetars have been found. Five of them are known as soft gamma repeaters, or SGRs, because they sporadically release large, short bursts (lasting about 0.1 s) of low energy (soft) gamma rays and hard X-rays. The rest, about 10, are associated with anomalous X-ray pulsars, or AXPs. Although SGRs and AXPs were first thought to be different objects, we now know that they share many properties and that their activity is sustained by their strong magnetic fields.

Magnetars are different from ‘ordinary’ neutron stars because their internal magnetic field is thought to be strong enough to twist the stellar crust. Like in a circuit fed by a gigantic battery, this twist produces currents in the form of electron clouds which flow around the star. These currents interact with the radiation coming from the stellar surface, producing the X-rays.

An artist's impression of XMM-Newton.   Credits: ESA (Image by C. Carreau)

An artist's impression of XMM-Newton. Credits: ESA (Image by C. Carreau)


Until now, scientists could not test their predictions, because it is not possible to produce such ultra-strong magnetic fields in laboratories on Earth.

To understand this phenomenon, a team led by Dr Nanda Rea from the University of Amsterdam used XMM-Newton and Integral data to search for these dense electron clouds around all known magnetars, for the first time.

Rea’s team found evidence that large electron currents do actually exist, and were able to measure the electron density which is a thousand times stronger than in a ‘normal’ pulsar. They have also measured the typical velocity at which the electron currents flow. With it, scientists have now established a link between an observed phenomenon and an actual physical process, an important clue in the puzzle of understanding these celestial objects.

The team is now working hard to develop and test more detailed models on the same line, to fully understand the behavior of matter under the influence of such strong magnetic fields.

Source: ESA


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LLDIAZ
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LLDIAZ
November 14, 2008 7:56 AM

Eric near buffalo _Your crazy!!

Now to matter at hand.
If massive stars collapse into magnetars how big do the stars have to be to collapse into blackholes?
and if a magnetar and a black hole have so much mass are they in some way connected?
can one over time become the other?.

Eric Near Buffalo
Guest
Eric Near Buffalo
November 14, 2008 7:45 AM

A teaspoon of neutron star matter would weigh 100 million tons? Wow.

How great would it be to trick some world class weight lifters with that?

“Your first task is to lift that teaspoon with the glowing material.”

“Ha…that’s a joke. ERGHHHHH! ERGHHHHHHHHHHHHHH!!! What the…? Is this thing glued to the table?”

Eric Near Buffalo
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Eric Near Buffalo
November 14, 2008 7:46 AM

“Ha…that’s a joke. ERGHHHHH! ERGHHHHHHHHHHHHHH!!! What the…? Is this thing glued to the table?”

Considering that it’s 100 million tons, it would have decimated the table. It should probably have been put on the ground. My bad.

Dark Gnat
Member
Dark Gnat
November 14, 2008 8:02 AM

Yeah, if a neutron star accretes enough material, then could collapse into a black hole. I don’t know what kind of radiation the event would produce.

If a neuron star has an electron cloud around it, couldn’t it be a giant model of an atom? smile

dbdncr
Member
dbdncr
November 14, 2008 8:05 AM

Assuming you could actually acquire a teaspoon of this substance… What would happen when it left the influence of the stars gravity?

Expand into a Rhode Island chunk of nuetrons?

Would it stay nuetrons?

ricardo rivaldo
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ricardo rivaldo
November 14, 2008 8:11 AM

If it is a neutron star, how could it have a magnetic field ? Aren’t they supposed to be related to electrons or particules with charge ?

NoAstronomer
Member
NoAstronomer
November 14, 2008 9:50 AM

@Eric: at 100 million tons per spoonful even solid rock wouldn’t hold it – it would simply bore it’s way through the crust!

@Ricardo: A neutron star is *mostly* neutrons and there’s a big difference between all neutrons and mostly neutrons.

Eric Near Buffalo
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Eric Near Buffalo
November 14, 2008 10:08 AM

@ No Astronomer: Very true. It would most likely leave a spoon shaped hole in the ground about 10 feet deep, maybe less – maybe more, depending on where the bedrock lies at any given location on the planet.

@ LLDIAZ: I’m not crazy, I just think a little differently smile

Eric Near Buffalo
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Eric Near Buffalo
November 14, 2008 10:14 AM

~~LLDIAZ Says:
November 14th, 2008 at 7:56 am
Now to matter at hand.
If massive stars collapse into magnetars how big do the stars have to be to collapse into blackholes?~~

Good question… and I can’t answer it. I can however speculate it may take a star the size of one reported a while back on here. If I recall correctly, there was a story on here about a star that was found semi-recently that possibly had the circumference of Saturn’s orbit. If that is correct from memory, that’s a bloody big star. Maybe that one would do the trick.

Sid
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Sid
November 14, 2008 10:37 AM

Is the shape of the magnetic field distorted by the gravity of the magnatar?

ZeTron
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ZeTron
November 14, 2008 11:32 AM

100 Million tons would be about 300 empire state building or 400 sears towers or 112 golden gate bridges. Or what? About all of the buildings in lower Manhattan?

Jon Hanford
Member
Jon Hanford
November 14, 2008 4:18 PM
@Sid, Yes, the magnetic field of a magnetar can easily be distorted by the gravity of a magnetar, and vice versa. Starquakes (rearrangement of the neutron star matter) can greatly modify the magnetic field of a magnetar, producing prodigous amounts of electromagnetic radiation in the process. Rapid fluctuations in the magnetic field of a magnetar can also generated enormous amounts of EM radiation from this compact object.. The key to both of these processes lies in the extreme density of the neutron star and the enormous strength of the magnetic fields involved in a magnetar. And just because a neutron star may present a neutral magnetic moment from the magnetar, the already established intense magnetic field of the… Read more »
Don Alexander
Member
Don Alexander
November 14, 2008 4:24 PM
Okay, some answers from a semi-expert… @Eric Near Buffalo and his idea: Actually, it would tunnel right though to the Earth’s core and almost up to the other side again before swinging back. 100 million tons placed on a surface of a few square inches?? That creates a pressure which penetrates anything! Even bedrock, mantle rock etc. But… …this leads us to a comment for dbdncr: Neutronium has both an upper and a lower mass limit. Concerning the upper mass limit and one question from LLDIAZ: There’s a mass named the Tolman-Oppenheimer-Volkov mass which is the neutron star version of the Chandrasekhar mass in white dwarfs. Exceed this mass, for example via additional accretion from a binary donor… Read more »
Eric Near Buffalo
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Eric Near Buffalo
November 17, 2008 7:37 AM

@ Don Alexander:
Wow, I really underestimated that.

Mike Kelley
Member
Mike Kelley
November 17, 2008 11:16 AM

Thank you Don. MOK

spam909
Member
spam909
November 17, 2008 2:08 PM

Quick novice question. If one where to land on a nuetron star, would the gravitational effects of the stars spinning make it impossible to move or even crush the person?

Don Alexander
Member
Don Alexander
November 18, 2008 7:32 AM

@spam: Some millisecond pulsars rotate so rapidly that they’re equators move at close to light speed, which in part cancels the immense gravity. The thing is, it doesn’t help against tidal forces, sou you’d still be torn to shreds.

There is no known substance in the universe which would not be squshed on the surface of a NS. And by squshed, I mean fusion-burned to iron…

bob
Guest
bob
November 18, 2008 8:48 PM

A teaspoon of neutron star material would not fall through the earth. Both the teaspoon and the earth would be drawn toward the neutron star material, falling onto it.

Don Alexander
Member
Don Alexander
November 20, 2008 2:10 PM

@bob: Actually, both attract each other. As do all things with mass. But considering the Earth weighs about 16 orders of magnitude more, I’m pretty sure having that teaspoon falling into the Earth is the better approximation.

Note that 1E8 tons is a small asteroid (roughly 400 meters diameter if spherical), the attractive force of such a spoonfull is still very small.

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