APOD: An Unexpected Flare from the Crab Nebula (2011 May 23)

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APOD: An Unexpected Flare from the Crab Nebula (2011 May 23)

Postby APOD Robot » Mon May 23, 2011 4:06 am

Image An Unexpected Flare from the Crab Nebula

Explanation: Why does the Crab Nebula flare? No one is sure. The unusual behavior, discovered over the past few years, seems only to occur in very high energy light -- gamma rays. As recently as one month ago, gamma-ray observations of the Crab Nebula by the Fermi Gamma Ray Space Telescope showed an unexpected increase in gamma-ray brightness, becoming about five times the nebula's usual gamma-ray brightness, and fading again in only a few days. Now usually the faster the variability, the smaller the region involved. This might indicate that the powerful pulsar at the center of the Crab, a compact neutron star rotating 30 times a second, is somehow involved. Specifically, speculation is centered on the changing magnetic field that surely surrounds the powerful pulsar. Rapid changes in this field might lead to waves of rapidly accelerated electrons which emit the flares, possibly in ways similar to our Sun. The above image shows how the Crab Nebula normally appears in gamma rays, as compared to the Geminga pulsar, and how it then appeared during the recent brightening.

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Re: APOD: An Unexpected Flare from the Crab Nebula (2011 May

Postby Beyond » Mon May 23, 2011 4:10 am

Hey, IF you were Crabby, You'd flare up once in a while too :!:
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Re: APOD: An Unexpected Flare from the Crab Nebula (2011 May

Postby owlice » Mon May 23, 2011 4:16 am

What a spectacular APOD, just chock full of information and great links!
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Re: APOD: An Unexpected Flare from the Crab Nebula (2011 May

Postby bystander » Mon May 23, 2011 4:26 am

Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk.
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Re: APOD: An Unexpected Flare from the Crab Nebula (2011 May

Postby amfrushour » Mon May 23, 2011 5:11 am

Will you feature an image of the Alpha Magnetic Spectrometer-02 that is newly installed on the International Space Station?
http://www.nasa.gov/images/content/550933main_s134e007532_hires_full.jpg

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Re: APOD: An Unexpected Flare from the Crab Nebula (2011 May

Postby bactame » Mon May 23, 2011 5:32 am

Is this an apod about Crab or Geminga? Geminga is more interesting since is 8 times closer to us than the Crab. Since the background changes more than Geminga does. Could Inflation of the Big Bang still be going on? Surely, i don't know but Steinhardt's article raises interesting questions about just how valid the Wiki claim of 300,000 years is.

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Re: APOD: An Unexpected Flare from the Crab Nebula (2011 May

Postby neufer » Mon May 23, 2011 11:13 am

bactame wrote:
Is this an apod about Crab or Geminga? Geminga is more interesting since is 8 times closer to us than the Crab. Since the background changes more than Geminga does. Could Inflation of the Big Bang still be going on? Surely, i don't know but Steinhardt's article raises interesting questions about just how valid the Wiki claim of 300,000 years is.

Geminga spins 7 times slower and is 300 times older than the Crab.

The Crab is mewling and puking in the nurse's arms.

Geminga shifts into the lean and slipper'd pantaloon, with spectacles on nose and pouch on side, his youthful hose, well saved, a world too wide for his shrunk shank; and his big manly voice, turning again toward childish treble, pipes and whistles in his sound.
---------------------------------------------------------------------
    . As You Like It Act 2, Scene 7

    JAQUES: All the world's a stage,
    And all the men and women merely players:
    They have their exits and their entrances;
    And one man in his time plays many parts,
    His acts being seven ages. At first the infant,
    Mewling and puking in the nurse's arms.
    And then the whining school-boy, with his satchel
    And shining morning face, creeping like snail
    Unwillingly to school. And then the lover,
    Sighing like furnace, with a woeful ballad
    Made to his mistress' eyebrow. Then a soldier,
    Full of strange oaths and bearded like the pard,
    Jealous in honour, sudden and quick in quarrel,
    Seeking the bubble reputation
    Even in the cannon's mouth. And then the justice,
    In fair round belly with good capon lined,
    With eyes severe and beard of formal cut,
    Full of wise saws and modern instances;
    And so he plays his part. The sixth age shifts
    Into the lean and slipper'd pantaloon,
    With spectacles on nose and pouch on side,
    His youthful hose, well saved, a world too wide
    For his shrunk shank; and his big manly voice,
    Turning again toward childish treble, pipes
    And whistles in his sound. Last scene of all,
    That ends this strange eventful history,
    Is second childishness and mere oblivion,
    Sans teeth, sans eyes, sans taste, sans everything.
Art Neuendorffer

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Re: APOD: An Unexpected Flare from the Crab Nebula (2011 May

Postby orin stepanek » Mon May 23, 2011 11:34 am

If man becomes a space traveler; the Crab may be something he doesn't want to get too close to. :wink:
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Re: APOD: An Unexpected Flare from the Crab Nebula (2011 May

Postby neufer » Mon May 23, 2011 1:04 pm

orin stepanek wrote:
If man becomes a space traveler; the Crab may be something he doesn't want to get too close to. :wink:

Click to play embedded YouTube video.
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Re: APOD: An Unexpected Flare from the Crab Nebula (2011 May

Postby Starswarm Magellan » Mon May 23, 2011 2:49 pm

Same thing happened to me when I was a teenager.

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Re: APOD: An Unexpected Flare from the Crab Nebula (2011 May

Postby Boomer12k » Mon May 23, 2011 3:57 pm

If a regular star like our Sun, can swell to red giant and then down to white dwarf with flares between expanding and contracting, heating again and expand and cool and contract, along the way, I see no reason why a star that went super nova, and is now a neutron pulsar should not do the same thing. It collapses and heats, so it flares, and expands a bit, then cools and contracts and collapses again, even if only a "RELATIVE" tiny bit, so there is a "FLARE" of gamma ray energy. There is no reason to think that just because it is compacted that it would not be doing something similar as it is a cooling star. It is just a tremendously traumatized star! Still in its death throws. And so it flares. Even if that expansion and contraction is not very much due to the material being in a compacted state, there would still be some leeway there.

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Re: APOD: An Unexpected Flare from the Crab Nebula (2011 May

Postby neufer » Mon May 23, 2011 4:13 pm

Starswarm Magellan wrote:
Same thing happened to me when I was a teenager.

TMI
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Re: APOD: An Unexpected Flare from the Crab Nebula (2011 May

Postby neufer » Mon May 23, 2011 4:38 pm

Boomer12k wrote:
If a regular star like our Sun, can swell to red giant and then down to white dwarf with flares between expanding and contracting, heating again and expand and cool and contract, along the way, I see no reason why a star that went super nova, and is now a neutron pulsar should not do the same thing. It collapses and heats, so it flares, and expands a bit, then cools and contracts and collapses again, even if only a "RELATIVE" tiny bit, so there is a "FLARE" of gamma ray energy. There is no reason to think that just because it is compacted that it would not be doing something similar as it is a cooling star. It is just a tremendously traumatized star! Still in its death throws. And so it flares. Even if that expansion and contraction is not very much due to the material being in a compacted state, there would still be some leeway there.

Just because our Sun is a 'regular' star doesn't mean that it is by any means 'simple.'

White dwarfs & neutron stars are tremendously simple stars
which is why we can understand so much about them without ever having seen one up close & personal.
----------------------------------------------------------------------------
Degenerate, a. [L. degeneratus, p. p. of degenerare to degenerate, cause to degenerate, fr. degener base, degenerate, that departs from its race or kind; de- + genus race, kind.] Having become worse than one's kind, or one's former state; having declined in worth; having lost in goodness; deteriorated; degraded; unworthy; base; low.
    ----------------------------------------------------------------------------
    ___ Comus by John Milton

    Elder Brother: Unmuffle ye faint stars, and thou fair Moon
    _ That wontst to love the travailers benizon,
    _ Stoop thy pale visage through an amber cloud,
    _ And disinherit Chaos, that raigns here
    _ In double night of darknes, and of shades...
    _ Such are those thick and gloomy shadows damp
    _ Oft seen in Charnell vaults, and Sepulchers
    _ Lingering, and sitting by a new made grave,
    _ As loath to leave the body that it lov'd,
    _ And link't it self by carnal sensualty
    _ To a *DEGENERATE* and degraded state.
    ----------------------------------------------------------------------------
    Jeremiah ii. 21.: I had planted thee a noble vine . . . : how then
    . Art thou turned into the *DEGENERATE* plant of a strange vine unto me?
    ----------------------------------------------------------------------------
    ___ The Two Gentlemen of Verona Act 5, Scene 4

    DUKE: The more *DEGENERATE* and base Art thou.
    ----------------------------------------------------------------------------
Art Neuendorffer

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Re: APOD: An Unexpected Flare from the Crab Nebula (2011 May

Postby Star*Hopper » Mon May 23, 2011 5:09 pm

orin stepanek wrote:If man becomes a space traveler; the Crab may be something he doesn't want to get too close to. :wink:


'f you've been keeping up, most everything we find or has been found, we don't wanta get too close to!
Welllllll.....might want to, but doing so is decidedly ill advised.

Our two main problems vis-a-vis space exploration are, first, finding things that won't outright just kill us.
And second, a way of gettin' there alive.
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Re: APOD: An Unexpected Flare from the Crab Nebula (2011 May

Postby Chris Peterson » Mon May 23, 2011 5:16 pm

Boomer12k wrote:If a regular star like our Sun, can swell to red giant and then down to white dwarf with flares between expanding and contracting, heating again and expand and cool and contract, along the way, I see no reason why a star that went super nova, and is now a neutron pulsar should not do the same thing. It collapses and heats, so it flares, and expands a bit, then cools and contracts and collapses again, even if only a "RELATIVE" tiny bit, so there is a "FLARE" of gamma ray energy. There is no reason to think that just because it is compacted that it would not be doing something similar as it is a cooling star. It is just a tremendously traumatized star! Still in its death throws. And so it flares. Even if that expansion and contraction is not very much due to the material being in a compacted state, there would still be some leeway there.

Actually, there is every reason to think that a neutron star can't change its volume. "Regular" stars can do so because they are gaseous bodies, and the mechanism of hydrostatic equilibrium necessarily results in large changes in volume when the energy output changes. Neutron stars are not gaseous, and do not produce energy (except in a narrow sense, through the transfer of momentum). Thus, the reasonable idea that, unlike "regular" stars, neutron stars that flare are likely doing so by interacting with their surrounding environment.
Chris

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Re: APOD: An Unexpected Flare from the Crab Nebula (2011 May

Postby Boomer12k » Mon May 23, 2011 6:05 pm

Chris Peterson wrote:
Boomer12k wrote:If a regular star like our Sun, can swell to red giant and then down to white dwarf with flares between expanding and contracting, heating again and expand and cool and contract, along the way, I see no reason why a star that went super nova, and is now a neutron pulsar should not do the same thing. It collapses and heats, so it flares, and expands a bit, then cools and contracts and collapses again, even if only a "RELATIVE" tiny bit, so there is a "FLARE" of gamma ray energy. There is no reason to think that just because it is compacted that it would not be doing something similar as it is a cooling star. It is just a tremendously traumatized star! Still in its death throws. And so it flares. Even if that expansion and contraction is not very much due to the material being in a compacted state, there would still be some leeway there.

Actually, there is every reason to think that a neutron star can't change its volume. "Regular" stars can do so because they are gaseous bodies, and the mechanism of hydrostatic equilibrium necessarily results in large changes in volume when the energy output changes. Neutron stars are not gaseous, and do not produce energy (except in a narrow sense, through the transfer of momentum). Thus, the reasonable idea that, unlike "regular" stars, neutron stars that flare are likely doing so by interacting with their surrounding environment.


Maybe there is some left over remnants of dust and gas that it is interacting with. Generally aren't gamma rays caused by explosions? Maybe there are still "rumblings" in this type of star. Plus with a surface temperature of around 1 million degrees, I would say that it is still producing some energy. That, magnetic fields in a quickly rotating body, is nothing but energy. Maybe from time to time that emits G.R.s.
http://www.astronomy.ohio-state.edu/~ry ... tes21.html

So maybe this star has not quite finished settling down.
Last edited by Boomer12k on Mon May 23, 2011 6:11 pm, edited 1 time in total.

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Re: APOD: An Unexpected Flare from the Crab Nebula (2011 May

Postby NoelC » Mon May 23, 2011 6:08 pm

Cool APOD.

orin stepanek wrote:If man becomes a space traveler; the Crab may be something he doesn't want to get too close to. :wink:

I was thinking almost that identical thought, what with intense radiation, wildly spinning magnetic fields, possible fluctuating electric fields, particles flying everywhere, unexpected flares. "Best when viewed from a safe distance", methinks.

This is even on the assumption that we've accomplished "regular" space travel, with appropriate protection and shielding for "typical" conditions.

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Re: APOD: An Unexpected Flare from the Crab Nebula (2011 May

Postby Boomer12k » Mon May 23, 2011 6:13 pm

NoelC wrote:Cool APOD.

orin stepanek wrote:If man becomes a space traveler; the Crab may be something he doesn't want to get too close to. :wink:

I was thinking almost that identical thought, what with intense radiation, wildly spinning magnetic fields, possible fluctuating electric fields, particles flying everywhere, unexpected flares. "Best when viewed from a safe distance", methinks.

This is even on the assumption that we've accomplished "regular" space travel, with appropriate protection and shielding for "typical" conditions.

-Noel



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Re: APOD: An Unexpected Flare from the Crab Nebula (2011 May

Postby Chris Peterson » Mon May 23, 2011 7:20 pm

Boomer12k wrote:Maybe there is some left over remnants of dust and gas that it is interacting with.

Certainly- that's what the Crab Nebula mostly consists of: left over dust and gas.

Generally aren't gamma rays caused by explosions?

No, gamma rays are merely high energy photons. They can be produced by many mechanisms. Of course, because of the high energies involved, they are often associated with events that might be described as "explosions", but they aren't caused by explosions.

Maybe there are still "rumblings" in this type of star.

Very unlikely. As Art pointed out previously, neutron stars are actually quite simple in most respects, meaning that they are probably well enough understood to discount the likelihood of "rumblings" or other such activity.

Plus with a surface temperature of around 1 million degrees, I would say that it is still producing some energy.

Being hot does not mean energy is being produced. A neutron star is hot because it is radiating away its residual heat. It is not producing energy internally.

That, magnetic fields in a quickly rotating body, is nothing but energy.

But not energy being produced... stored energy being dissipated.
Chris

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Re: APOD: An Unexpected Flare from the Crab Nebula (2011 May

Postby neufer » Mon May 23, 2011 9:22 pm

Chris Peterson wrote:
Boomer12k wrote:
Maybe there are still "rumblings" in this type of star.

Very unlikely. As Art pointed out previously, neutron stars are actually quite simple in most respects, meaning that they are probably well enough understood to discount the likelihood of "rumblings" or other such activity.

Image
Well... I wouldn't go that far; both crabs & neutron stars
have crusts that need 'adjustments' from time to time.

http://en.wikipedia.org/wiki/Starquake_ ... #Starquake wrote:
<<A starquake is an astrophysical phenomenon that occurs when the crust of a neutron star undergoes a sudden adjustment, analogous to an earthquake on Earth. This is thought to be the source of the giant gamma ray flares that are produced approximately once per decade from soft gamma repeaters. Starquakes are thought to be caused by huge stresses exerted on the surface of the neutron star produced by twists in the ultra-strong interior magnetic fields.

The largest recorded starquake occurred on the ultracompact stellar corpse (magnetar) SGR 1806-20. It released gamma rays equivalent to 1036 kW in intensity. This starquake occurred 50,000 light years away; had it occurred within ten light years of Earth, it could have potentially caused a mass extinction.>>

http://www.nasa.gov/centers/goddard/new ... quake.html wrote:
NASA Sees Hidden Structure of Neutron Star in Starquake
Susan Hendrix, Goddard Space Flight Center 04.25.06

<<Scientists using NASA's Rossi X-ray Timing Explorer have estimated the depth of the crust on a neutron star, the densest object known in the universe. The crust, they say, is close to a mile deep and so tightly packed that a teaspoon of this material would weigh about 10 million tons on Earth. The measurement, the first of its kind, came courtesy of a massive explosion on a neutron star in December 2004. Vibrations from the explosion revealed details about the star's composition. The technique is analogous to seismology, the study of seismic waves from earthquakes and explosions that reveal the structure of the Earth's crust and interior. This new seismology technique provides a way to probe a neutron star's interior, a place of great mystery and speculation. Pressure and density are so intense here that the core might harbor exotic particles thought to have existed only at the moment of the Big Bang.

Tod Strohmayer of NASA Goddard Space Flight Center in Greenbelt, Md., presents this result in a press conference today at the April meeting of the American Physical Society in Dallas. "We think this explosion, the biggest of its kind ever observed, really jolted the star and literally started it ringing like a bell," said Strohmayer. "The vibrations created in the explosion, although faint, provide very specific clues about what makes up these bizarre objects. A neutron star's ring depends on how waves pass through layers of differing density, either slushy or solid."

A neutron star is the core remnant of a star once several times more massive than the sun. A neutron star contains about 1.4 solar masses of material crammed into a sphere only about 12 miles across. Strohmayer and Watts examined a neutron star named SGR 1806-20, about 40,000 light years from Earth in the constellation Sagittarius. The object is in a subclass of highly magnetic neutron stars called magnetars.

On December 27, 2004, the surface of SGR 1806-20 experienced an unprecedented explosion. As reported by NASA and the National Science Foundation in early 2005, this was the brightest X-ray flash ever seen from beyond our solar system. The explosion, called a hyperflare, was caused by a sudden change in the star's powerful magnetic field that cracked the crust, likely producing a massive starquake. The event was detected by several space observatories, including the Rossi Explorer, which observed the X-ray light emitted. Strohmayer and Watts think that the oscillations are evidence of global torsional vibrations within the star's crust. These vibrations, like waves moving through a rope, are analogous to the S-waves observed during terrestrial earthquakes. Their study, building on observations of vibrations from this source by GianLuca Israel of Italy's National Institute of Astrophysics, found several new frequencies during the hyperflare. Watts and Strohmayer subsequently confirmed their measurements using NASA's Ramaty High Energy Spectroscopic Solar Imager, a solar observatory that also recorded the hyperflare. And they found the evidence for a high-frequency oscillation at 625 Hz, indicative of waves traversing the crust vertically.

The abundance of frequencies---similar to a chord, as opposed to a single note---enabled the scientists to estimate the depth of the neutron star crust. This is based on a comparison of frequencies from waves traveling around the star's crust and from those traveling radially through it. The diameter of a neutron star is uncertain, but based on the estimate of about 12 miles across, the crust would be about 1 mile deep. This figure, based on the observed frequencies, is in line with theoretical estimates.

Starquake seismology holds great promise for determining many neutron star properties. Strohmayer and Watts have analyzed archived Rossi data from a dimmer 1998 magnetar hyperflare (from SGR 1900+14) and found telltale oscillations here, too, although not strong enough to determine the crust thickness. A larger neutron star explosion detected in X-rays might reveal deeper secrets, such as the nature of matter at the star's core. One exciting possibility is that the core might contain free quarks. Quarks are the building blocks of protons and neutrons, and under normal conditions are always tightly bound together. Finding evidence for free quarks would aid in understanding the true nature of matter and energy. Laboratories on Earth, including massive particle accelerators, cannot generate the energies needed to reveal free quarks.

"Neutron stars are great laboratories for the study of extreme physics," said Watts. "We'd love to be able to crack one open, but since that's probably not going to happen, observing the effects of a magnetar hyperflare on a neutron star is perhaps the next best thing.">>

http://nrumiano.free.fr/Estars/neutrons.html wrote:
<<Following the explosion of a supernova, a neutron star is created with a temperature probably over 1000 billion degrees. It will rapidly cool in less than 1000 years, to 1 million degrees. After that, its temperature will decrease much more slowly. At its birth, this neutron star is recovering the rotation of the previous star, following the conservation of angular momentum . It will rotate at a very high speed. The Crab pulsar inside the nebula, for example, spins 30 times a second.

Until recently, one supposed that a neutron star began by rotating at a very high speed, and slowed down with time. This scenario seems satisfactory for a lone star, but in the case of a binary system, where the companion is a small sized star, magnetic coupling effects with the forming accretion disk seems to cause a later acceleration of the spinning speed.

The powerful magnetic and electrical field which surrounds the star will generate a thin beam of light, in the radio-wave frequencies. This beam sweeps across the sky, in the same way a lighthouse beam sweeps across the sea. These stars are called pulsars. Because the magnetic axis of the pulsar is not aligned with its rotational axis, the radio emission, generated by particles trapped in the magnetic field lines, will sweep across the sky, like a lighthouse beam sweeps across the sea. Some pulsars rotate a few hundred times per second. The rotation of a pulsar is exceedingly precise, and can be used as a cosmic clock. In particular, the system known as PSR 1913+16, made up of two pulsars, allowed the scientists to measure the very small effects of gravitational waves, predicted by general relativity.
-----------------------------------------------------------------------
Magnetars

Neutron stars exhibit a very powerful magnetic field, anchored to their surface. This field comes from the magnetic field of the initial star, compressed by the collapse of the supernova. It is about 1012 Gauss, i.e. a trillion times more powerful than the Earth's magnetic field. The core of a neutron star is an electrical conductor, because it contains a trace of free electrons and protons. If the star is born rotating fast enough (at least 200 rev/second), the liquid core is able to start a "dynamo action" during the first 20 seconds or so, which is enough to enhance the magnetic field eight hundred to one thousand times (about 8x1014 Gauss).

The magnetic field rotates with the star, being anchored to its surface. With such a strength, the magnetic waves and the related, magnetically-powered charged particles will carry off the star's rotational energy in a very efficient way, and suddenly brake its spinning movement. In some thousand years, the spinning velocity of the star will become as low as one revolution every five to ten seconds. Such a star is called a magnetar (contraction of magnetic star). When a magnetic field is this powerful, it can move material in the star's interior, and so apply very high stresses over the solid crust ; sometimes this crust can break, in the same way that the Earth's crust breaks in an earthquake under the stresses. At this time, the star ejects bursts of highly energetic particles, which will produce a brief, but intense emission of hard X-rays (the neutron star radiates at this moment as much energy as the Sun radiates in 1000 years).

This radiation emission can repeat sporadically. This phenomenon is called : Soft Gamma Repeaters. Some magnetars radiate X-rays with a period of about ten seconds : they are called AXP : Anomalous X-ray Pulsars. This radiation comes from hot matter trapped inside the lines of the magnetic field, rotating with the star. After 10,000 years, the magnetic energy source in these stars begins to run down, and the magnetar slowly becomes invisible. It is possible that 10% of neutron stars are magnetars.
-----------------------------------------------------------------------
Strange stars

If the mass of the neutron star is high enough, the density in its core can be so high that the appearance of inside a neutron starheavy particles could become possible : hyperons, pions ... In fact, nobody really knows what can happen, because the theory about the strong interaction (which rules the environment) under high density is not currently understood well enough.

An hypothesis imagined in 1984 by the physicist Edward Witten would be the quark deconfinement, with the outbreak of a plasma of quarks u and d and gluons, under the effect of an external excitation - an high energy cosmic ray for example. This plasma is unstable and these quarks can desintegrate, giving now quarks s (strange). This core of quarks s and gluons is going to convert progressively the remaining neutrons of the star, to finally end in a total transformation (with a possible exception of a fine crust) in strange matter - so called, because mainly made up of quarks s . This very fast transformation, between one second and no more than ten minutes, leads to a "quark star", also called "strange star".

Such a star is not ruled only by gravitation, but essentially by quantum chromodynamics (QCD). So, it has no minimal mass, and a radius proportional to its mass. A strange star would typically have a mass between one and two solar masses, and a radius about 10km, less than the radius of a neutron star.

The fact that the star has a crust or no leads to great consequences for observations : if the star does not have a crust, it will not emit any visible light. Conversely, if it has a crust of nuclear matter, its surface properties will be the same as a neutron star, and could for example to behave as a pulsar - a very fast pulsar because the radius of the star is less and the quark-gluon plasma is more viscous than the liquid of neutrons.

Theoretical models forecast a faster cooling for a quark star than for a neutron star, but this could be questioned if a superfluidity phenomenon arises in the neutron star, drastically lowering its caloric value.

In 1996, the ROSAT satellite discovered an X-ray source, called RX J1856.6-3754 at about 450 light years of the Earth. Later measurements by the Chandra observatory seem to indicate a diameter of about 10 km for the star, too little for a neutron star. Obviously, this measurement is liable to doubt, the accuracy of measurement of such a little diameter at such a distance being very relative. Other similar neutron stars have been discovered since this one, but the measurement -indirect, of course- of their sizes is always very difficult and subject to many errors.

At last, some astrophysicists are doubting about the very existence of strange stars, not on a theoretical point of view, but because of the lack of a simple and realistic scenario to create them. The conditions to create a black hole, as we are about to discover, are much easier to fulfill than the ones necessary to create a strange star.>>
Art Neuendorffer

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Re: APOD: An Unexpected Flare from the Crab Nebula (2011 May

Postby NoelC » Mon May 23, 2011 9:49 pm

Some fascinating info there, neufer. Starquakes, eh? Wow.

Stupid question, but if "heat" is the kinetic energy of atoms moving around "bouncing off" one another, how does a neutron star carry heat? Are the neutrons in a white hot neutron star not packed quite so densely that they are held still, but are actually bouncing off one another in a very confined space with great force? Or do the subatomic particles that make up neutrons vibrate?

A corrollary question: If a neutron star were to cool sufficiently, might it just collapse into a black hole?

a neutron star's interior, a place of great mystery and speculation


I realize such states of matter defy conventional visualizations, and we may be discussing theory. I just find it fascinating to think about, but I have little education on the subject.

-Noel

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Re: APOD: An Unexpected Flare from the Crab Nebula (2011 May

Postby Devil Particle » Mon May 23, 2011 10:03 pm

Question: In both images there appear to a lot of reddish clumps between the crab and geminga. In the flare picture they appear more illuminated. Are these actual objects (or dust?) or are they optical 'noise' from the telescope being used?

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Re: APOD: An Unexpected Flare from the Crab Nebula (2011 May

Postby neufer » Tue May 24, 2011 11:15 am

NoelC wrote:
Stupid question, but if "heat" is the kinetic energy of atoms moving around "bouncing off" one another, how does a neutron star carry heat? Are the neutrons in a white hot neutron star not packed quite so densely that they are held still, but are actually bouncing off one another in a very confined space with great force? Or do the subatomic particles that make up neutrons vibrate?

Actually this is a rather difficult question for me to answer. Clearly the radiation is coming from the crust of the neutron star and/or some sort of iron 'photosphere' on top of that crust and I really don't understand the physics going on here. I would guess that the crust is crusty only because of high magnetic fields making tiny cyclotron atoms out of the iron nuclei while simultaneously decoupling up neutron magnetic dipoles from down neutron magnetic dipoles. But it's really something that I can't quite get my head around.

Certainly an 'ideal' degenerate neutron star would be in its lowest possible quantum state and therefore could not radiate at all in spite of tremendous quantum kinetic energies (much as an atom in its ground state cannot radiate). Actual neutron stars do have most of their matter as degenerate neutrons in their ground state but the outer neutrons are still in a chaotic excited state and these are the particles that radiate.
NoelC wrote:
A corollary question: If a neutron star were to cool sufficiently, might it just collapse into a black hole?

A radiating neutron star is losing mass (m=E/c2) not gaining it.

Only the accretion/collision of matter from another star can cause
a neutron star to pass the mass limit so as to collapse into a black hole.
Art Neuendorffer

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Re: APOD: An Unexpected Flare from the Crab Nebula (2011 May

Postby neufer » Tue May 24, 2011 11:31 am

Devil Particle wrote:Question: In both images there appear to a lot of reddish clumps between the crab and geminga. In the flare picture they appear more illuminated. Are these actual objects (or dust?) or are they optical 'noise' from the telescope being used?

The primary reddish blob between the Crab and Geminga is associated with a known active galactic nuclei (AGN).

Flip the picture over (to put Geminga on top as it should be) and compare:

http://apod.nasa.gov/apod/ap090709.html
http://apod.nasa.gov/apod/ap100318.html
Art Neuendorffer

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Re: APOD: An Unexpected Flare from the Crab Nebula (2011 May

Postby DavidLeodis » Tue May 24, 2011 2:09 pm

I was staggered at the sheer number of authors in the report brought up by the "past" link in the explanation. Out of interest I tried to count them but I gave up at 50 when I was still well under half-way! :o


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