PDA

View Full Version : Tumbling Neutron Star



Fraser
2006-Apr-20, 10:41 PM
SUMMARY: ESA's orbiting X-ray telescope, the XMM-Newton space observatory, has located a neutron star that's out of control. Researchers found that its temperature rose steadily for more than four years, but now it's starting to decrease again. The object's overall temperature isn't changing, it's just tumbling, and slowly displaying different areas to observers here on Earth - like a wobbling top. These observations will help astronomers understand some of the internal processes that govern these kinds of objects.

View full article (http://www.universetoday.com/am/publish/xmm-newton_tumbling_star.html)
What do you think about this story? post your comments below.

antoniseb
2006-Apr-21, 12:49 PM
Can a rotating object precess if there is not some torque on it? I'm trying to picture what options are available to explain this. Since it is a pulsar, I'm assuming we've already ruled out massive companions through timing studies.

Gerald Lukaniuk
2006-Apr-21, 05:50 PM
Can a rotating object precess if there is not some torque on it? I'm trying to picture what options are available to explain this. Since it is a pulsar, I'm assuming we've already ruled out massive companions through timing studies.
EXCELLENT POINT
If the jets are not bi directional, equal and opposite or fluttering precisely simultaneous, tumbling and spiraling with respect to the rest of the universe should result. While the pulses represent minute thruat compared to mass we are dealing with angler momentums in free space over millions of years. Although you's think neutron matter would be an incredible conductor of heat if this object has stopped pulsing(opps- emittting jets)

Grand_Lunar
2006-Apr-21, 08:06 PM
I wonder if it was struck by something (what could send such an object tumbling?).

A very strange phenomanon indeed.

antoniseb
2006-Apr-21, 08:26 PM
It doesn't seem to be tumbling so much as precessing.

Wild speculation: However, you could imagine that there might be some state where the nuetrons or hyperons in the core are superfluid under some circumstances, and viscous under others, and that a change in the magnetic field could potentially make enough of the spinning/flowing mass of this object change direction in such a way that the outer surface tumbles.

Gerald Lukaniuk
2006-Apr-21, 09:57 PM
It doesn't seem to be tumbling so much as precessing.

Wild speculation: However, you could imagine that there might be some state where the nuetrons or hyperons in the core are superfluid under some circumstances, and viscous under others, and that a change in the magnetic field could potentially make enough of the spinning/flowing mass of this object change direction in such a way that the outer surface tumbles.
You're right I think a lot of contradictions about the behavior of neutron stars and pulsars point to a new form of matter coming in a number of varieties like the chemical elements.

trinitree88
2006-Apr-21, 10:35 PM
You're right I think a lot of contradictions about the behavior of neutron stars and pulsars point to a new form of matter coming in a number of varieties like the chemical elements.

There is as yet no known reason why the sun flips it's magnetic field every ~ 11 years, inducing a 22 year total solar cycle...( though the paperback book..."The Jupiter Effect" tried to point to the gravitational/magnetic interaction of Jupiter's ~10.5 year period as intrinsic. If Jupiter is not Sol-ly responsible (pun-intended), then there's a piece of physics to figure out here.
Extrapolated to neutron stars...a field flip would result in a jet flip...and since jet emission would be inherently asymmetrical...parity effects...the cumulative result of multiple polarity flips would be ....precisely precession.:dance: :think:

Gerald Lukaniuk
2006-Apr-24, 01:27 AM
There is as yet no known reason why the sun flips it's magnetic field every ~ 11 years, inducing a 22 year total solar cycle...( though the paperback book..."The Jupiter Effect" tried to point to the gravitational/magnetic interaction of Jupiter's ~10.5 year period as intrinsic. If Jupiter is not Sol-ly responsible (pun-intended), then there's a piece of physics to figure out here.
Extrapolated to neutron stars...a field flip would result in a jet flip...and since jet emission would be inherently asymmetrical...parity effects...the cumulative result of multiple polarity flips would be ....precisely precession.:dance: :think:

That would certainly be worth considering. When you considerer the sun is like a small super heavy magnet surrendered by a ball of glow slime with a Styrofoam powder crust floating in space it wouldn't take much to flip its little belly. An 11 years cycle certainly sounds like an orbiting or passing extra solar influence. We could be talking a small dark nasty super cold super magnet (~ -400K!) some type of ion stream or our cutting through magnetic lines of force between a couple of magnetic monster so far apart that we might not know theyíre engaged . Total magnet force is an M1 M2 relationship and the earthís core is embedded in a more viscous environment so perhaps we donít experience a great enough tug to invert our poles physically or re-magnetize them. The reversals could indicate something swinging back and forth in a 22 year cycle.
I havenít read the Jupiter theory but I can imagine with a year the last almost 4000 days the Jovians must throw the biggest New Year bash in the solar system. Albeit a little chillier than Times Square. Neverthe less is wise of them not to invite Sol to warm things up but it certainly must make him flip his top.

Relmuis
2006-Apr-26, 03:39 PM
Wouldn't a neutron star precess if it is sitting in an external magnetic field?

antoniseb
2006-Apr-26, 07:27 PM
Probably. Can you calculate how strong a field it would have to be to get the speed of precession that fast?

Relmuis
2006-Apr-28, 02:32 PM
A neutron star has a mass comparable to the mass of the Sun, which is 2*1030 kg. It will therefore contain some 1058 neutrons. Assuming that the magnetic moments of these neutrons are randomly orientated, their total magnetic moment would be 1029 times the magnetic moment of a single neutron. The latter is roughly 10-26 J/T, so the star would have a magnetic moment of 103 J/T.

If the neutron star is a sphere with more or less equal density throughout, its moment of intertia is 0,4 times its mass (2*1030 kg) times the square of its radius (which I take to be 104 m). Therefore a rotation at a rate of 1 Hz (once every few seconds) entails an energy of some 1038 J. For this, the field strength should be of the order of 1035 T.

However, the neutrons may be aligned with each other. I have no idea whether this is probable, or even possible; I think it would depend on the star's temperature, but someone else would have to look into this. If all the neutrons are perfectly aligned, the field strength can be a factor 1029 lower, and a 106 T field would be enough to give a 1 Hz precession.

trinitree88
2007-Mar-24, 01:18 PM
A neutron star has a mass comparable to the mass of the Sun, which is 2*1030 kg. It will therefore contain some 1058 neutrons. Assuming that the magnetic moments of these neutrons are randomly orientated, their total magnetic moment would be 1029 times the magnetic moment of a single neutron. The latter is roughly 10-26 J/T, so the star would have a magnetic moment of 103 J/T.

If the neutron star is a sphere with more or less equal density throughout, its moment of intertia is 0,4 times its mass (2*1030 kg) times the square of its radius (which I take to be 104 m). Therefore a rotation at a rate of 1 Hz (once every few seconds) entails an energy of some 1038 J. For this, the field strength should be of the order of 1035 T.

However, the neutrons may be aligned with each other. I have no idea whether this is probable, or even possible; I think it would depend on the star's temperature, but someone else would have to look into this. If all the neutrons are perfectly aligned, the field strength can be a factor 1029 lower, and a 106 T field would be enough to give a 1 Hz precession.

Relmuis. Interesting. I attended a talk at MIT by a German Prof. at the Center for Astrophysics a few years ago...name is eluding me...I'll check. His work was on equations of state for neutron stars indicating that their (nucleons)..sphericity was affected, and that they were more stretched out like beans in the interior of the star. Models using the bean shape, which is easier to give macroscopic aligning, gave better results for crustal "quakes".pete

http://www.springerlink.com/content/k5x3594535855000/

GOURDHEAD
2007-Mar-25, 11:25 AM
Is it reasonable to assume that the material within a neutron star is homogeneous and that the shape is very oblate due to the high rate of spin?

trinitree88
2007-Mar-25, 01:15 PM
Is it reasonable to assume that the material within a neutron star is homogeneous and that the shape is very oblate due to the high rate of spin?

Gourdhead. Oblateness is addressed here. It's actually not large, but the graphic needs to show that to define the parameters.see:
http://www.slac.stanford.edu/econf/C041213/papers/2306.PDF

publiusr
2007-Apr-30, 10:00 PM
So this thing could sling radiation in all kinds of directions...