Starship Asterisk*

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.

• . 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.

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

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

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.

• ----------------------------------------------------------------------------
  ___ 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.
  ----------------------------------------------------------------------------

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

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.

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.

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

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.

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

Boomer12k wrote: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.

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.

http://en.wikipedia.org/wiki/Starquake_%28astrophysics%29#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/news/topstory/2006/starquake.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.
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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.
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Strange stars

Strange stars in the night?

---

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.>>

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

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?

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

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?