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Astronomy Without A Telescope – Making Sense Of The Neutron Zoo

Article Updated: 24 Dec , 2015

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The spectacular gravity of neutron stars offers great opportunities for thought experiments. For example, if you dropped an object from a height of 1 meter above a neutron star’s surface, it would hit the surface within a millionth of a second having been accelerated to over 7 million kilometers an hour.

But these days you should first be clear what kind of neutron star you are talking about. With ever more x-ray sensitive equipment scanning the skies, notably the ten year old Chandra space telescope, a surprising diversity of neutron star types are emerging.

The traditional radio pulsar now has a number of diverse cousins, notably magnetars which broadcast huge outbursts of high energy gamma and x-rays. The extraordinary magnetic fields of magnetars invoke a whole new set of thought experiments. If you were within 1000 kilometres of a magnetar, its intense magnetic field would tear you to pieces just from violent perturbation of your water molecules. Even at a safe distance of 200,000 kilometres, it will still wipe all the information off your credit card – which is pretty scary too.

Neutron stars are the compressed remnant of a star left behind after it went supernova. They retain much of that stars angular momentum, but within a highly compressed object only 10 to 20 kilometers in diameter. So, like ice skaters when they pull their arms in – neutron stars spin pretty fast.

Furthermore, compressing a star’s magnetic field into the smaller volume of the neutron star, increases the strength of that magnetic field substantially. However, these strong magnetic fields create drag against the stars’ own stellar wind of charged particles, meaning that all neutron stars are in the process of ‘spinning down’.

This spin down correlates with an increase in luminosity, albeit much of it is in x-ray wavelengths. This is presumably because a fast spin expands the star outwards, while a slower spin lets stellar material compress inwards – so like a bicycle pump it heats up. Hence the name rotation powered pulsar (RPP) for your ‘standard’ neutron stars, where that beam of energy flashing at you once every rotation is a result of the braking action of the magnetic field on the star’s spin.

It’s been suggested that magnetars may just be a higher order of this same RPP effect. Victoria Kaspi has suggested it may be time to consider a ‘grand unified theory’ of neutron stars where all the various species might be explained by their initial conditions, particularly their initial magnetic field strength, as well as their age.

It’s likely that the progenitor star of a magnetar was a particularly big star which left behind a particularly big stellar remnant. Thus, these rarer ‘big’ neutron stars might all begin their lives as a magnetar, radiating huge energies as its powerful magnetic field puts the brakes on its spin. But this dynamic activity means these big stars lose energy quickly, perhaps taking on the appearance of a very x ray luminous, though otherwise unremarkable, RPP later in their life.

Other neutron stars might begin life in less dramatic fashion, as the much more common and just averagely luminous RPPs, which spin down at a more leisurely rate – never achieving the extraordinary luminosities that magnetars are capable of, but managing to remain luminous for longer time periods.

The relatively quiet Central Compact Objects, which don’t seem to even pulse in radio anymore, could represent the end stage in the neutron star life cycle, beyond which the stars hit the dead line, where a highly degraded magnetic field is no longer able to apply the brakes to the stars’ spin. This removes the main cause of their characteristic luminosity and pulsar behaviour – so they just fade quietly away.

For now, this grand unification scheme remains a compelling idea – perhaps awaiting another ten years of Chandra observations to confirm or modify it further.

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Olaf
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Olaf
May 15, 2010 11:41 AM

Oh oohhh dirty words in the article. . I bet many responses

DrFlimmer
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DrFlimmer
May 15, 2010 12:24 PM

It doesn’t fit with the topic of this particular thread, but what I find astonishing are “neutron star-quakes”. The crust moves only a few millimeters, if at all, and releases an enormous amount of energy! I think, some of those outbreaks have been accidentally classified as Supernovae at first.

IVAN3MAN_AT_LARGE
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IVAN3MAN_AT_LARGE
May 16, 2010 2:02 AM

[I]f you dropped an object from a height of 1 meter above a neutron star’s surface, it would hit the surface within a millionth of a second having been accelerated to over 7 million kilometers an hour.

Well, if that object has a mass of 1 kg, and E(k) = ½mv², then the kinetic energy of that object will be over 1.89E+12 joules — equivalent to approximately 452,000 tonnes of T.N.T.

IVAN3MAN_AT_LARGE
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IVAN3MAN_AT_LARGE
May 16, 2010 2:07 AM

(I’m relieved that the XML/HTML codes have worked above!)

jimhenson
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jimhenson
May 16, 2010 10:20 AM
I believe in a grand unification with neutron stars and black holes. Goodsell says a link between cold atoms and carbon nanotubes form atomic black holes with ions orbiting like stars. Davies says W3AA massive protostar is self-similar to small mass star formations. Relativisitic supernovas like SN2009bb have the luminoisity of a quasar with a central engine core, rather then the luminosity of a galaxy for a supernova. Dark matter is not consumed by black holes, cause I believe magnetic fields mistaken for dark matter “gravity” aligns galactic positron anti-matter, accretion disks, and dark matter with the BEC emission jet. Tidal streams clumping into galaxy halos have unaltered dispersion in the leading tail compared to the trailing tail,… Read more »
IVAN3MAN_AT_LARGE
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IVAN3MAN_AT_LARGE
May 16, 2010 1:30 PM

@ Jon Hanford,

You’re welcome! That’s what I’m here for.

Torbjörn Larsson OM:

Somewhere a little rabbit is crying now, I’m sure.

I found that poor bunny here.

Lawrence B. Crowell
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Lawrence B. Crowell
May 16, 2010 7:02 AM
The idea of a “grand unification” of neutron stars probably requires some understanding of the interior state of these objects. A basic neutron star is a gas of neutrons with Fermi-Dirac statistics. Given enough mass though the interior will become dominated by higher mass baryons, such as the Sigma^0 in the spin 1/2 octet. So the core of the neutron star may be in a different phase in general. For larger neutron stars the core may be dominated by quark-gluon plasma. From the perspective of magnetism this state has analogies to the superconducting state. This may be an aspect of how magnetars function to permit these incredible magnetic field above the 10^{13] Gauss range. LC
frogstar
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frogstar
May 16, 2010 7:44 AM

The recent paper from Kaspi giving a compact overview of neutron star types can be found here:

http://arxiv4.library.cornell.edu/abs/1005.0876v1

(for those of you who like me didn’t notice at first that the name of the author was a link to the paper)

jimhenson
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jimhenson
May 16, 2010 3:53 PM

none of you people know anything of special value yourself, yet alone anything about the grand unification theory by Einstein. nor do bunnies have anything to contribute for the advancement of science. that’s why you’re so anxious to second request removal post deletions, without discussing serioius science about the relevant topic. Neutron stars have black hole centers that warp space and collide because of dark matter streaming magnetism pulling other stars together. Get your acts together and apply observational phenomena with neutron stars like Kaspi says!

jimhenson
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jimhenson
May 16, 2010 5:07 PM

The suns solar wind H+ southern hemisphere emission is invisible to us along the magnetic plane of the solar system including earths orbit. extending out to 100 AU is this edge boundary of the solar system that deflects back the solar wind U-turn style. The suns magnetic field is polar with north pole always opposite to earth’s pole. From earth we can only always see and observe just along the East-West equator of the sun. Dark matter invisible magnetic field lines from the suns southern hemisphere tidal streams and pulls together distant gases stars into galaxies etc. white dwarf stars continually merge from brown dwarf and red dwarf stars without a single nemesis for the sun.

IVAN3MAN_AT_LARGE
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IVAN3MAN_AT_LARGE
May 16, 2010 10:06 AM

@ Lawrence B. Crowell,

Here’s a nice illustration of “The Guts of a Neutron Star“.

Jon Hanford
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Jon Hanford
May 16, 2010 11:23 AM

Thanks for that link, IVAN3MAN. I see it touches on a topic not mentioned in the above article. I’m referring to the spinup of accreting neutron stars with large magnetic fields ( http://www.astro.umd.edu/~miller/nstar.html#accretion ). This mechanism is thought to give rise to millisecond pulsars.

Torbjorn Larsson OM
Member
Torbjorn Larsson OM
May 16, 2010 11:31 AM

Could someone please delete the crackpot comment that spewed irrelevant promotion of “personal theories” on this beautiful page? Somewhere a little rabbit is crying now, I’m sure. (-_-‘)

DrFlimmer
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DrFlimmer
May 16, 2010 12:34 PM

I second Torbjorn Larsson’s request!

Olaf
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Olaf
May 16, 2010 12:57 PM

Me too: I second Torbjorn Larsson’s request!

Aqua4U
Member
May 16, 2010 5:18 PM

What I like is that at this distance we have seen motion(s) over time in the pulsar! Rare to see? at least astronomically speaking its so…

Its alive! with pulsating electro dynamic plasma’s spinning outward around a magnetically constraining toroid. What other incredible properties of matter will we discover as we dig deeper into this mystery? What fantastic engine powers this dynamo? Gravity?

Interdimensional wormholes anyone? Where FTL is possible in dimension ‘A’? because time itself runs at a different relative rate and/or direction?

Lawrence B. Crowell
Member
Lawrence B. Crowell
May 16, 2010 6:32 PM
@IVAN3MAN_AT_LARGE: Thanks for the page on neutron star interiors. I have little knowledge of this area. The interior is of course the question mark. I am not sure we will ever get much data on that. @ Jon, What you are mentioning is the sort of inverse of the spin down mechanism. With a huge magnetic field the neutron star will be dragged into a sort of equilibrium with the motion of the plasma medium. A nonrotating medium will slow down the pulsar, and an accretion disk will spin it up. @ jimhenson : A black hole in the interior of a neutron star would quickly convert the whole thing into a black hole. Unfortunately what you wrote,… Read more »
Dark Gnat
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Dark Gnat
May 16, 2010 6:34 PM

Strange, I thought black holes and neutron stars didn’t work with EU, and were just a bunch of hocus pocus.

I guess now that there is an article that contains “neutron stars”, “plasma”, and “magnetic fields” together, everything is just fine.

IVAN3MAN_AT_LARGE
Member
IVAN3MAN_AT_LARGE
May 16, 2010 9:08 PM

@ Lawrence B. Crowell,

You’re welcome! As for the question mark on the interior of a neutron star, without a few mysteries the scientific pursuit for knowledge would stop.

Torbjorn Larsson OM
Member
Torbjorn Larsson OM
May 17, 2010 1:09 AM

Steve, thanks for taking out the garbage!

IVAN3MAN, thanks, that is exactly my bunny friend. I just looked again, and he is now happily munching his lettuce.

@ LBC:

The AdS physics within the BPS system might have amplitudes that are black hole-like.

To bone up on this further, tangentially this reminded me, the likelihood that black hole-like coherent quantum objects exist should have gone up with the discovery of quantum many-body interactions besides simple entanglement in “everyday” Bose-Einstein condensates. It’s a long stretch, but… What do you think?

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