Neutron Stars, Pulsars, and Magnetars

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Artist rendition of pulsar courtesy of nrao.edu

I have decided to create this thread in an attempt to shed some light on a very interesting astronomical phenomenon that a lot of the general public are unfamiliar with unless they have interests in astronomy or are in formal classes. I will be covering neutron stars, a couple kinds of pulsars, and magnetars. While all of these are stars, they are very different from the normal visualization of a star many people imagine when thinking about one. These stars are just another shining example of the complete strangeness and wonder in the Universe. So without further hesitation let’s begin!

Chapter Summary
1. Neutron Stars
2. Pulsars
3. Magnetars


1.Neutron Stars

A neutron star is the remaining core, or remnant of a massive star that is much more massive than our Sun, such as a Red Giant that has ended its’ life cycle in a specific type of supernova that is caused by what is known as a core collapse, which is caused by the gravity of the star being to much to support itself anymore. The remaining core is normally no larger than a city like Manhattan on Earth but contains around 1.4 times the mass of our Sun! If you could take a teaspoon and ‘scoop the matter’ out of the neutron star it would weigh one billion tons! A neutron star’s magnetic field is about 1 quadrillion times stronger than Earths. A neutron star is still very hot despite plasma (solar atmosphere) no longer being around it. A neutron star is one of many ends a star can take, even more massive stars that have cores of around 5 solar masses and higher end up as the famous black holes, but we will not get into those here. The name “neutron star” comes from the fact that the star is comprised of nearly all neutrons. The escape velocity of a neutron star is 33% the speed of light, so in a way you could say that the neutron star is the stage right ‘below’ a black hole due to its’ extreme gravity caused by its very high mass. Neutron stars do rotate rather quickly, usually several times a second, with some rotating several hundred times a second. This is caused by the conservation of angular momentum. The closest known neutron star to Earth is PSR J0108-1431 , which is a pulsar (next chapter) and is only 280 light years away. There are over 1300 confirmed neutron stars and a believed 10^5 in the Milky Way.

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Image depicting layers, in which the surface is a crystalline iron crust, of neutron star courtesy of wikipedia.org

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Image of PSR J0108-1431 courtesy of chandra.harvard.edu

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Image showing common size of a neutron star in relation to the Grand Canyon courtesy of Chandra.harvard.edu , the quark star pictured is only theoretical and not relevant to this thread.


2.Pulsars

Another type of neutron star, pulsars are a rapidly spinning neutron star that shoots jets of X-rays, radio waves, and sometimes gamma rays at very near the speed of light (186,000 mps) from its’ strong magnetic poles. This type of neutron star also has a powerful magnetic field. The observed time between their pulses is between 1.4 milliseconds and 8.5 seconds. Some pulsars have a rotational period as accurate as an atomic clock. A pulsar is best described as exactly analogous to a lighthouse in how it looks and behaves. Obviously the name “pulsar” comes from how the star pulses light and other electromagnetic radiation as it spins. Some pulsars, such as PSR B1257 +12 are known to have planets orbiting them, which are called pulsar planets. The exact mechanism of how exactly pulsars emit beams of electromagnetic radiation is still unknown, although they have been known to exist since being discovered in July of 1967. It is believed to possibly result from complex electromagnetic processes that take place at the highly magnetized poles of a neutron star. Although the exact mechanism is still not understood. Sometimes pulsars will emit EM radiation in the visible light spectrum of the EM field.

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X-ray image of supernova Kes 75, the blue light in the center is the pulsar. Image courtesy of sciencedaily.com

There are several different sub categories of pulsars, millisecond pulsars are simply pulsars with millisecond rotational periods, so they obviously spin very quickly. These are normally found in a binary star system and are believed to be accreting, or pulling material to them from its’ sister star. As mentioned above, some pulsars emit radiation in the radio band of the spectrum, those are called radio pulsars and are thought to be powered by their rapid rotational period. Some emit the electromagnetic radiation in the X-ray band of the spectrum, those are accordingly called X-ray pulsars, and are thought to be powered by the accretion of a sister star in its’ binary orbit. Gamma ray pulsars are pulsars that emit radiation in the gamma band of the spectrum. Binary pulsars are pulsars that have a companion star, usually another pulsar, white dwarf, or neutron star. Binary pulsars mainly emit X-ray radiation.Anomalous X-ray pulsars are now believed to actually be magentars (next chapter) because of their very strong magnetic fields and slow rotational periods of 5 to 12 seconds. It is now commonly believed that pulsars and magentars are actually the same thing, just in different stages of neutron star evolution. Further more is postulated that a neutron star can change from a pulsar to magnetar and vice versa, the ones that have been observed doing so are called periodic pulsars.

However, one of these flashing lighthouses has surprised observers… it exploded, blasting vast amounts of energy into space, and then continued to spin and flash as if nothing had happened. This phenomenon has recently been observed by NASA's Rossi X-ray Timing Explorer (RXTE) and has been backed up by data from the Chandra X-ray Observatory.

There are in fact other classes of neutron star out there. Slow-spinning, highly magnetic "magnetars" are considered to be a separate type of neutron star. They are distinct from the less-magnetic pulsar as they sporadically release vast amounts of energy into space and do not exhibit the periodic rotation we understand from pulsars. It is believed that magnetars explode as the intense magnetic field (the strongest magnetic field believed to exist in the Universe) warps the neutron star surface, causing extremely energetic reconnection events between magnetic flux, causing violent and sporadic X-ray bursts.

There is now speculation that known periodic pulsars that suddenly exhibit magnetar-like explosions are actually the highly magnetic cousins of pulsars disguised as pulsars. Pulsars simply do not have enough magnetic energy to generate explosions of this magnitude, magnetars do.

Fotis Gavriil of NASA's Goddard Space Flight Center in Greenbelt, and his colleagues analysed a young neutron star (called PSR J1846-0258 in the constellation Aquila). This pulsar was often considered to be "normal" due to its fast spin (3.1 revolutions per second), but RXTE observed five magnetar-like X-ray bursts from the pulsar in 2006. Each event lasted no longer than 0.14 seconds and generated the energy of 75,000 Suns. Follow up observations by Chandra confirmed that over the course of six years, the pulsar had become more "magnetar-like". The rotation of the pulsar is also slowing down, suggesting a high magnetic field may be braking its rotation.

These findings are significant, as it suggests that pulsars and magnetars may be the same creature, just at different periods of a pulsars lifetime, and not two entirely different classes of neutron star

www.universetoday.com...

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Rotating Radio Transients (RRAT) is also evidence for neutron stars being highly transistionable between pulsars and magnetars. As their rotation rate is like a magnetar but they emit very brief and very ‘bright’radio pulses. It is also important to note that astronomers believe that exploding pulsars are responsible for a large amount of gamma ray bursts. It is also important to reiterate that pulsars can and do emit more than one specific band of EM radiation, although one band is normally in much higher concentration than others.
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Diagram explaining pulsar mechanics courtesy of nasa.gov

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Another example showing the strong magnetic field and emission beams courtesy of wikipedia.org


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On…

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Off…

Text and X-ray image showing a pulsar in the Crab Nebula “on” and when it is “off” (EM beams away from Earth) courtesy of nasa.gov


Image showing geometry and mechanics of pulsars courtesy of nasa.gov

Some notable pulsars…

•

The first radio pulsar CP 1919 (now known as PSR 1919+21), with a pulse period of 1.337 seconds and a pulse width of 0.04 second, was discovered in 1967.[15] A drawing of this pulsar's radio waves was used as the cover of British rock band Joy Division's debut album, "Unknown Pleasures".
• The first binary pulsar, PSR 1913+16, whose orbit is decaying at the exact rate predicted due to the emission of gravitational radiation by general relativity
• The first millisecond pulsar, PSR B1937+21
• The brightest millisecond pulsar, PSR J0437-4715
• The first X-ray pulsar, Cen X-3
• The first accreting millisecond X-ray pulsar, SAX J1808.4-3658
• The first pulsar with planets, PSR B1257+12
• The first double pulsar binary system, PSR J0737−3039
• The longest period pulsar, PSR J2144-3933
• The most stable pulsar in period, PSR J0437-4715
• The magnetar SGR 1806-20 produced the largest burst of energy in the Galaxy ever experimentally recorded on 27 December 2004
• PSR B1931+24 "... appears as a normal pulsar for about a week and then 'switches off' for about one month before emitting pulses again. [..] this pulsar slows down more rapidly when the pulsar is on than when it is off. [.. the] braking mechanism must be related to the radio emission and the processes creating it and the additional slow-down can be explained by a wind of particles leaving the pulsar's magnetosphere and carrying away rotational energy.
• PSR J1748-2446ad, at 716 Hz, the pulsar with the highest rotation speed.
• PSR J0108-1431, the closest known pulsar to the Earth. It lies in the direction of the constellation Cetus, at a distance of about 85 parsecs (280 light years). Nevertheless, it was not discovered until 1993 due to its extremely low luminosity. It was discovered by the Danish astronomer Thomas Tauris. in collaboration with a team of Australian and European astronomers using the Parkes 64-meter radio telescope. The pulsar is 1000 times weaker than an average radio pulsar and thus this pulsar may represent the tip of an iceberg of a population of more than half a million such dim pulsars crowding our Milky Way.
• PSR J1903+0327, a ~2.15 ms pulsar discovered to be in a highly eccentric binary star system with a sun-like star.
• A pulsar in the CTA 1 supernova remnant initially emitted radiation in the X-ray bands. Strangely, when it was observed at a later time X-ray radiation was not detected. Instead, the Fermi Gamma-ray Space Telescope detected the pulsar was emitting gamma ray radiation, the first of its kind.

en.wikipedia.org...


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Image of optical/X-ray composite of pulsar in Crab Nebula, notice the emission beam seen and the swirling look of the nebula cloud caused by ‘pulsar wind’. The pulsar wind is caused by the high speed of the particles shooting from the pulsar as well the strong magnetic field. Courtesy of wikipedia.org.

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Image of Vela Pulsar in the middle of its surrounding pulsar wind nebula courtesy of wikipedia.org



3.Magnetars

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Image of artists depiction of a magnetar courtesy of universetoday.com

Magnetars are yet another manifestation a neutron star can take. Magnetars have an extremely powerful magnetic field, hence the name, when it decays it releases powerful amounts of X-rays and gamma rays. A magnetar does not pulse ‘beacons’ of radio or light energy from its poles like a pulsar. Like neutron stars and pulsars, a magnetar is no bigger than 12 miles in diameter but extremely dense with mass. They rotate very slowly compared to pulsars, although some do not as we will see later on. The closest discovered magnetar to Earth is 13,000 lightyears distant.Magnatars have a relatively short life of around 10,000 years, after which they become ‘inactive’ and essentially revert back to a neutron star. The magnetic fields of magnetars can often reach ten gigateslas in strength, for comparison the Earth has a field strength of 30-60 microteslas. It is thought that the field is so strong it would kill humans within 1000 kilometers of it. Also it is thought that a magnetar could wipe all magnetic credit card bands clean from a distance of halfway to the Moon, or about 100,000 miles. It is thought that one out of ten supernovae result in a magnetar forming, as opposed to the more common neutron star or pulsar. As of May 2007 only twelve magnetars have been confirmed, with more awaiting confirmation. Magnetars are also thought responsible for GRB’s (gamma ray bursts) and soft gamma repeaters. The magnetars magnetic field is so strong it twists its own crust which produces currents that form electron clouds around the star, which interact with the radiation coming from the stellar surface to form X-rays and gamma rays. Stellarquakes, sometimes called “Magnetar Quakes” or “Pulsar Quakes” occur in both a magnetar and a pulsar. They 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. Sometimes the quakes can be so bad that they cause the very powerful GRBs. Sometimes magnetars and pulsars under go what is called a glitch, which is the sudden speeding up of the stars rotational period and a large increase in energy. It can last from days to years. It is thought that this is another cause of starquakes, particularly in pulsars. In 2004 a quake on a pulsar 50,000 lightyears away arrived in our solar system, temporarily knocking out every X-ray satellite in space. Had this event happened within ten lightyears from Earth it would have caused a mass extinction similar to the Permian Extinction. This should show you how much energy is expended by these stars. Luckily now astronomers and astrophysicist can now predict these quakes:

Scientists have discovered how to predict earthquake-like events in pulsars. These explosive episodes likely crack a pulsar's dense crust and momentarily bump up its spin rate.

Using NASA's Rossi X-ray Timing Explorer, the team has tracked about 20 "starquakes" on one particular pulsar over the past eight years and uncovered a remarkably simple, predictive pattern.

heasarc.gsfc.nasa.gov...

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Image of rendering of a starquake courtesy of nasa.gov

As mentioned earlier it now appears that pulsars and magnetars can transition between each phase, possibly many times. Like pulsars, magnetars have migrating poles, similar to what we see here on Earth.

On February 21, 2008 it was announced that NASA and McGill University researchers had discovered a neutron star that temporarily changed from a pulsar to a magnetar. This indicates that magnetars are not merely a rare type of pulsar but may be a (possibly reversible) phase in the lives of at least some pulsars.

en.wikipedia.org...

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Another rendition of a magnetar, courtesy of astroengine.com

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Image showing a GRB from a magnetar in the Aquila constellation courtesy ofwikipedia.org , notice the magnetic field looking rings around the star. They are 7 lightyears in diameter.


Well that about wraps up the thread, realize that this was in a introduction type format and there are many more things that were not covered. For further information I would suggest any of the references I used or to simply Google any information. You can also consult your local library or school library if you are in high school or college. Neutron stars, pulsars, and magnetars are, as we’ve seen, some very interesting entities in our ever growing universe of wondrous and strange things. Astronomers and astrophysicist are constantly learning new things about these stars and other phenomena in the Universe. I hope that this information and the following video will help shed some light on these things and maybe get those who aren’t interested in space and physics more interested. The following video explains neutron stars, pulsars, magnetars, and periodic pulsars. YouTube is a great tool to learn some basic to intermediate information from, especially the videos from the series The Universe. I hope everyone enjoys the videos.




**For more good videos I suggest anything from The Universe series.

References and Related Threads

References

nasa.gov

wikipedia.org

sciencedaily.com

universetoday.com



Related Threads

The next missions to the moon

Mars Exploration timeline

My Related Threads

Astronomy 101

Orbital Mechanics 101

On Parallel Universes

On Superluminal Propulsion




[edit on 6/20/2009 by jkrog08]

[edit on 6/20/2009 by jkrog08]

Very Interesting.. Good Post...

But, I'm curious about one picture, the one with the two stars in relation to the grand canyon. ....

Can't these stars be of multiple sizes? I mean... not all neutron stars are the same size? Are they? If not, thats a little misleading...

reply to post by jkrog08


Wow, what an AMAZING thread! Such quality and I actually learned something. Which makes it even more the wilder. The lay out is perfect and it is just I have printed this out and will study this more, but wow what an excellent amount of research and explainations. Fantastic mate, this thread is top notch.

I haven't watched the videos yet. But its awesome.

Damn good thread mate.

Keep it up,
~TheMythLives

reply to post by ThreeDeuce


Thanks,neutron stars (pulsars and magnetars included) can get no larger than about 12 miles in diameter because of their rapid spin.

Sweet! I'd never heard of magnetars before, so that part was an interesting read. Thanks!

reply to post by DragonsDemesne


Magnetars are totally amazing, they are probably my favorite type of star, although the hypnotizing light show put on by a pulsar is close by. The best ones are the ones that change back and forth between a pulsar and magnetar, the periodic pulsars.

S+F & 1 line post I run Einstien@home - I would like others to also run it!

reply to post by Now_Then


I heard about that, binary pulsars give excellent opportunities to study gravitational wave theory.

reply to post by jkrog08


Positively excellent thread! I have been considering going into the study of Astronomy myself, and this is just a good eye-opener for people who think the universe if just filled with a bunch of twinkling little stars, all the same, with similar purpose.

Very informative, man.

reply to post by undefy.gravity


Thanks, maybe you should go into astronomy. I am going to school to be a cosmologist myself. I love space, I am always trying to get others interested in it,lol it is funny because when I talk with my friends they do not even care or understand a lot of what I want to talk about when it comes to science and such. Unfortunately there is not too many great places here in Tennessee to see a true clear sky, at least that I have ever been, but I am sure there is.

reply to post by jkrog08


Well, I tried sending a u2u over your way, but that was unsuccessful. I was trying to infer on your ideas on getting involved with space-related studies in TN. I am in Tennessee as well, and right up the road from me is the local university's Planetarium! I am trying to get on board with that, but was curious as to if you had any suggestions as for where else there is to look into these sort of studies.

reply to post by jkrog08

jk! That's top-of-the-line stuff! That's what I call excellent research! And needless to say, you've brought out some very relevant aspects.

However, you'll always have detractors....like me, in the case of Pulsars, for example! For starters, I wonder if you've taken into account the possibility of the reality of the Electric Universe concept? A majority of mainstream scientists look at it with a lot of skepticism. Since it's not been proved either way, I have an open mind in this theory.

That said, let's see what a Pulsar could be according to the Electric universe theory:

According to Healy & Peratt, the light-house-like massive stars rotating at 60,000 rpm are difficult to imagine. With that rpm, a star that size would be ripped apart due to massive centrifugal forces. The pulsar repetition rates are most probably due to an electrical oscillation. And I tend to agree here.

They begin their (peer reviewed) paper with a review of the history of the discovery of pulsars and the classical theoretical descriptions of their behavior and performed a plasma supported transmission line experiment that duplicated 17 detailed properties of those observed emissions.

Postulating this theory as an explanation for observed pulsar emissions is far less of a stretch of one's sense of reality than proposing that an incredibly massive star rotates with the speed of a dentist's drill. Healy & Peratt

Imagine a star rotating at thousands of rpm! Doesn't sound logical. Needless to say, most would contend that the tremendous forces of gravity within the Pulsar keeps it from being ripped apart, but that's way beyond logic!

There's other stuff that doesn't gel too, like 'black holes', though in response to a question I had put forth to Dr Michio Kaku he said that these are a reality and all over the universe. But I still have my doubts on this concept until proved beyond doubt! Just plain deductions based on mathematical calculations of what should be there and what shouldn't by producing something out of nothing in order to try and balance the equations is what we're doing right now. There may be many more parameters that need to be taken into account in those equations that we haven't the slightest clue about at this juncture!

Cheers!

Originally posted by jkrog08
reply to post by ThreeDeuce

 

Thanks,neutron stars (pulsars and magnetars included) can get no larger than about 12 miles in diameter because of their rapid spin.

I think the volume is also limited by the mass of the neutron star. Too many neutrons make a black hole, so it must have a limit to the size it can reach, the spin being irrelevant in such a case.

You can't compress a neutron star anymore than it already is -- IE, adding more neutrons may increase the volume for a little bit, but at a certain volume, gravity would overcome the ability of the neutrons to "resist" each other, collapsing the neutrons into a singularity.

I love Magnetars. Great Post!!

Can someone also do one about "Brown Dwarfs" my favorite star ever.

Thank You.

reply to post by mikesingh


Thanks, yes I based this on the current models of the Universe. Personally I have not looked into the electric model that much (at all really,lol) but I think the star not ripping apart can be attributed to the high gravity, as well the extreme compaction of the neutrons, as well the weak force's strong binding properties under the extreme compression of the mass. I do agree however, that scientist are starting to make up things to fill their equations and that is not right.

reply to post by jkrog08


Good stuff Justin

Some handy, basic info on some of those wonderful things filling the void.

The info is doubly handy as you can apply it to insults and sound intelligent at the same time. Say for example:

"Mate you're as dense as a neutron bloody star!"

Or words to that effect.

Now to try it out on someone.... Has anybody seen Zorgon???




[edit on 21-6-2009 by mckyle]

reply to post by mckyle


LOL, thanks. I didn't think of that one, I might have to use it.

Originally posted by jkrog08
I do agree however, that scientist are starting to make up things to fill their equations and that is not right.

You may be more correct than you think, neutronium is a fictional substance and cannot exist apparently according to the island of stability principle in nuclear physics. The limit is something like 1.5 neutrons per proton. Any difference and they spontaneously undergo radioactive transformation to meet this ratio.

Still astrophysicists insist that gravity is capable of achieving this feat, it is quite miraculous stuff. They also believe pulsars a thousand or more solar masses can spin faster than a dentist drill.

I appreciate your efforts jkrog, I don't mean to rain on a nicely presented thread. But yeah they're makin this stuff up.