How do millisecond pulsars remain intact?

[wolram]

http://en.wikipedia.org/wiki/Millisecond_pulsar

How do these pulsars remain intact?

 

[SpaceTiger]

The neutron star's own gravity holds it together.

 

[wolram]

The neutron star's own gravity holds it together.

Thanks ST, that is the generally accept idea.

 

[-RA-]

i think that a star spinning that fast would be very inplausible. we are talking of 38,500rpm, surely that's not likely to be correct?

I looked into that millisecond pulsar and it has some interesting characteristics.

1. The duty cycle is typically 5% (ie, the time it is on is much shorter than the time in between pulses.)
2. Some individual pulses are quite variable in intesity.
3. The polarization of the pulse implies that the origin has a strong magnetic field.

These characteristics are nearly exactly the same as those observed with an electric arc (lighning) interaction between two closely spaced binary stars. It is a basic 'relaxation oscillator' system. I read a good paper that looks into alternative interpretations of the pulsar readings, http://adsabs.harvard.edu/abs/1995Ap&SS.227..229H , it too suggests a periodic electrical plasma discharge mechanism in its conclusions.

I think this becasue the NRL have detected five optical companion stars orbiting millisecond pulsars, three of which are the amoung the coolest and oldest white dwarf stars known. (To be precise one of them is called PSR B1937+21 if you want to look it up).

any ideas? which interpretation is more likely?

 

[SpaceTiger]

i think that a star spinning that fast would be very inplausible. we are talking of 38,500rpm, surely that's not likely to be correct?

The paper you cite is not refuting the idea that pulsars are rotating -- there are no mainstream alternatives to the rotating pulsar model. The theoretical difficulty with pulsars is explaining the generation of their emission. That paper is attempting to distinguish between emission models.

Please be sure you fully understand something before trying to create a controversy. Many of your posts have been overly presumptuous in this regard.

 

[Lockheed]

i think that a star spinning that fast would be very inplausible. we are talking of 38,500rpm, surely that's not likely to be correct?

There are many that can spin faster then that. Milisecond pulsars are not that uncommon either. Here is some info on the fastest yet discovered: http://www.nrao.edu/pr/2006/mspulsar/

Other than that, SpaceTiger is quite right. It is sheer gravity that holds it together at those speeds. Of course, there are limits to what size they can be in order for them to stay intact.

 

[-RA-]

what is the typical diameter of the rotating section of the pulsar?

 

[SpaceTiger]

what is the typical diameter of the rotating section of the pulsar?

The entire star is rotating. Neutron stars are typically ~20 km in diameter.

 

[-RA-]

The paper you cite is not refuting the idea that pulsars are rotating -- there are no mainstream alternatives to the rotating pulsar model. The theoretical difficulty with pulsars is explaining the generation of their emission. That paper is attempting to distinguish between emission models.

Please be sure you fully understand something before trying to create a controversy. Many of your posts have been overly presumptuous in this regard.

I did not claim that pulsars don’t rotate, just that the pulses we detect from them may not be due to the proposed emission points on a rotating surface. Maybe I was not specific enough, The particular sentences in that paper that made me think this are;"Because of the losses in the dielectric media and in synchrotron emission, the periodicity of the propagating pulses increases. However the experiment dramatically showed that there are glitches, the flow of electron flux across the magnetosphere, can shorten the line and concomitantly the period.
The fractional frequency stability scaling versus measurements interval up to about 30,000,000 s for pulsars is nearly identical to that for trapped-ion clocks. This supports the pulsar surface-magnetosphere relativistic double layer model; itself a trapped ion mechanism..."

"Both simulation and experiment suggest that micro-pulses and sub-pulses are produced by particle-wave interactions in non-uniform plasma eradiated by the electromagnetic wave. This effect is produced when the magnetically insulated voltage pulse reaches the pulsar surface. Because of the curvature, magnetic insulation is lost and plasma flows across this region. This tends to create a resonating or modulating component to the proper current pulse..."

and their conclusion,

"The source of the radiation energy may not be contained within the pulsar, but may instead derive from either the pulsars interaction with its environment or by energy delivered by an external circuit (Alfven 1981). This hypothesis is consistent with both the long term memory effect of the time averaged pulse and the occurrence of nulling, when no sub-pulses are observed. As noted earlier, our results support the 'planetary magnetosphere' view (Michael 1982) where the extent of the magnetosphere, not emission points on a rotating surface, determines the pulsar emission."Also there’s also some good data at http://www.mssl.ucl.ac.uk/~sz/Conference_files/pres/kuzmin.pdf , who also say that these very high energy bursts are likely caused by an recurring electrical discharge in the pulsars local environment.

 

[SpaceTiger]

Also there’s also some good data at http://www.mssl.ucl.ac.uk/~sz/Conference_files/pres/kuzmin.pdf , who also say that these very high energy bursts are likely caused by an recurring electrical discharge in the pulsars local environment.

I call BS. This presentation is talking about rare giant pulses, not the ones that occur every rotation period that you clearly thought you were talking about in your first post. You're talking way out of your depth and the original question was answered, so I think this thread is done.