New Class of Pulsars Discovered

xyz writes "NASA's Fermi Gamma-ray Space Telescope has discovered a new class of pulsars which emit purely in gamma rays. A pulsar is a rapidly spinning neutron star, and of the nearly 1,800 cataloged so far, only a small fraction emit at frequencies higher than radio waves. The gamma-ray-only pulsar, which lies within a supernova remnant known as CTA 1, is silent across parts of the electromagnetic spectrum where pulsars are normally found, indicating a new class of pulsars. It is located 'about 4,600 light-years away in the constellation Cepheus. Its lighthouse-like beam sweeps Earth's way every 316.86 milliseconds. The pulsar, which formed in a supernova explosion about 10,000 years ago, emits 1,000 times the energy of our sun.'"

Comments

First Pulsar Post

[Fishead]

Odd thing is that the signal seems to be carrying a message. We have decoded it, and it seems to read: F-I-R-S-T---P-O-S-T-.

Re:First Pulsar Post

[aliquis]

Funny, over here the only thing I can hear is fap-fap-fap...

Pulsar music

[CRCulver]

There was a recent Slashdot discussion on music from pulsars which didn't get quite the attention I wish it did. Along those lines, I'd again encourage all nerds here to check out Gerard Grisey's work Le Noire d'Etoile for six percussionists. This work is based in part on the periodicity of a certain pulsar, and at one moment the performers pause while the sound of another pulsar is acquired with a radio telescope and relayed over speakers in the hall. This would definitely appeal to the many nerds here with an astronomy bent, but it sadly remains little-known outside of IRCAM circles.

Re:Pulsar music

[CRCulver]

Ugh, I'm losing my French. The title is "Le Noir de l'Etoile". Sorry.

Re:Pulsar music

[Whiteox]

I, of course, was going to pick you up on that... Apology accepted.

Re:Pulsar music

[pod]

Along the same lines, I would recommend Arecibo (Atmosphere label) and Bad Sector (Old Europa Cafe, Waystyx) fairly obscure, but inspired by "astronomic" phenomena.

This proves they're from Chicago...

[800DeadCCs]

This proves they're from Chicagoland...
CTA....
3 busses will come within 316.86 milliseconds of each other,
then you'll wait 10,000 years for the next one.

Re:This proves they're from Chicago...

[dotancohen]

3 busses will come within 316.86 milliseconds of each other,
then you'll wait 10,000 years for the next one.

You obviously do not smoke. A surefire way to make that next bus come is to light one up.

Re:This proves they're from Chicago...

[Artuir]

Wait, light a cigarette or a bus up? I'd think lighting a bus on fire would defeat the purpose, but it would certainly draw attention.

Re:This proves they're from Chicago...

[thesandtiger]

A slight correction:

Three *nearly empty accordion buses* will quickly come, all of them the 29 State, and then you'll die of old age waiting for a 144.

Not that I'm bitter.

Re:This proves they're from Chicago...

[MikeDirnt69]

You can light the entire box, but if it's raining, no bus will ever arrive.

Technically

[Lord Byron II]

Since "emitting" usually has an implied "per second" in it, we should be talking about the power it emits, not the energy.

Re:Technically

[Fluffeh]

What about the person who emits a "funky odor"? We don't start trying to quantify that little bastard :)

Re:Gamma ray bursts and extinction events?

[Anonymous Coward]

> Should we hide in our basements
Check

> crack our neighbour's heads open and feast on the goo inside?
Now theres something on your to do list!

Emitted or recieved

[EdZ]

It's not mentioned in the article, and I assume it's so obvious that it was ruled out before announcement, but is there anything to suggest that the pulsar is pulsing across all frequencies up to Gamma, and that intervening matter is simply blocking all but the high-energy Gamma portion of the pulse? Or am I just mixing up black-body emission and emission by electron's jumping a band-gap.

Re:Emitted or recieved

[glitch23]

It's not mentioned in the article, and I assume it's so obvious that it was ruled out before announcement, but is there anything to suggest that the pulsar is pulsing across all frequencies up to Gamma, and that intervening matter is simply blocking all but the high-energy Gamma portion of the pulse?

Yes it was mentioned:

This discovery by Fermi is different because it is a purely gamma-ray pulsar. The star is silent across parts of electromagnetic spectrum where pulsars are normally found and hints at a whole population of previously unsuspected pulsars waiting to be picked out of the heavens.

Re:Emitted or recieved

[EdZ]

My point was: did they merely not DETECT wavelengths other than Gamma, or have they shown that wavelengths other than Gamma are not EMITTED? No mention is made of what tests can and/or have been done to determine which is true.

Re:Emitted or recieved

[Gil-galad55]

The radio emission is believed to come from a small patch near the surface of the neutron star called the polar cap. Hence, to see it, the pulsar has to be aligned just so with the line of sight to the Earth. Gamma ray emission appears to originate at a higher altitute, so there are more orientations of the pulsar with respect to the line of sight where we can see gamma rays. It's a geometrical effect.

Re:Emitted or recieved

[ceoyoyo]

It would have to be some pretty special intervening dust to block everything but gammas. Astronomers usually use radio and infrared to see through dust.

Re:Emitted or recieved

[Gil-galad55]

As I noted below, there is surely radio emission -- we are just not positioned to see it. The implication is that gamma ray emission originates higher in the pulsar magnetosphere than radio emission, so it paints a broader "beam" on the sky as the pulsar rotates.

Re:Gamma ray bursts and extinction events?

[thomasdz]

> crack our neighbour's heads open and feast on the goo inside?

Now theres something on your to do list!

The original Simpson's quote is from "Homer the Vigilante" http://www.simpsoncrazy.com/episodes/1F09

Re:Puny Humans

[Fex303]

I suggest we all go selectively breed and send our offspring to face trials of horrors. It's for the good of humanity.

Dad? Is that you?

Re:It's all supposition

[dotancohen]

No natural object is spinning that fast.

You are obviously not aware about the United States forefathers in their graves, knowing what is going on in that nation.

Re:I got a C in

[morgan_greywolf]

Quantum mechanics you insensitive prick!

If only you hadn't looked at the report card. Then, your grade could've been an A or an F, and you wouldn't have known until you looked at the report card, thus collapsing the waveform.

And now you know why you only got a C.

So, does this imply anything special?

[Jugalator]

Is there more to this than just a new object? Does it imply that certain models on how pulsars form need to be refined? Gamma rays are also incredibly high energy, what does it imply as for the structure of the pulsar that it doesn't emit lower frequencies?

What I'm getting at is pretty much that the article seem to just pass this off as a "ok, we have a new kind of pulsar here" without any follow up questions raised. IS there any questions to raise? Does this all fit neatly into what we know about pulsars, and is it easily explained why this one doesn't emit in lower frequencies, and only in a very high energy one?

I'm also surprised there are so much "junk" like the "yourmumisapulsar" tag and Obama posts, etc. Come on now, this is Slashdot, if I want the other stuff on science stories, I can read Digg. :-(

Re:So, does this imply anything special?

[play_in_traffic]

Gamma ray does not in fact imply much about energy (although they can be incredibly high energy). It is just another photon. What it does say is that it comes from a nuclear interaction rather than an electronic transition (electron mediated). This most certainly does say something about the nature of the pulsar that is generating this "beam" of ionizing radiation. Please let me know when you have a new model that accounts for this.

Re:So, does this imply anything special?

[Gil-galad55]

No, gamma rays from pulsars are much higher energy than those associated with nuclear transitions (typical scale: 1 MeV; pulsar emission spectra peak at 1 GeV, 1000 times greater).

Pulsars have extremely strong electromagnetic fields and are hence able to accelerate electrons up to very high energies. These electrons then scatter low energy photons upwards in energy to the gamma ray regime.

To answer GP's question, observing radio-quiet pulsars like this on in CTA1 tells us more about the gamma ray emission mechanism. Several different models exist, and the primary difference is where in the pulsar's magnetosphere gamma rays are created. In the polar cap model, gamma rays originate in a small patch near the magnetic pole, the same place as the radio emission. So, if gamma rays predominantly come from the polar cap, we shouldn't see radio-quiet pulsars. Hence, this pulsar favors an emission model with gamma rays from higher altitude, in the so-called outer gaps and slot gaps.

Re:So, does this imply anything special?

[Bemopolis]

Well, there should be a gamma-ray line at about 511 keV (0.024 A) in all pulsars, since the polar magnetic field strength generates electron-positron pairs, which then annihilate. This produces a broad line (it's a two-photon process), whic has been observed in other pulsars (iirc).

What's surprising here is the absence of thermal emission from other plasma in the magnetic field which, as you imply, impacts the pulsar at the magnetic poles to produce heat (and hence light.) The question is then, where is this plasma that we usually see trapped in the pulsars' magnetic field. Since this pulsar is no longer inside its parent supernova remnant bubble, I would argue that that this plasma has just been left behind. Why the general interstellar medium has not somewhat replaced it is a bit of a mystery, but that's why we build telescopes in the first place: to find out.

Re:So, does this imply anything special?

[jmichaelg]

Gamma ray does not in fact imply much about energy (although they can be incredibly high energy). It is just another photon.

Huh!? Does Planck's constant ring a bell? ...

E = h * f

Gamma rays are very high frequency, hence they're highly energetic.

Re:So, does this imply anything special?

[Gil-galad55]

Well, there is clearly enough circumstellar (circumpulsar?) material to generate the pulsar wind nebula detected in X-rays, but as with all collisionless shocks, this material must be tenuous.

Re:Gamma ray bursts and extinction events?

[rasputin465]

Isn't earth in danger of an extinction event when a gamma ray burst occurs from something about 6,000 light years away?

Although this thing does emit gamma rays, in discreet packets, this is not an example of the phenomenon knows as Gamma Ray Bursts (GRBs). The "burst" in a genuine GRB lasts much longer (seconds or minutes as opposed to milliseconds), happens only once, and contains orders of magnitude greater energy.

So when we say we're screwed if a GRB happens within 6,000 lt-yr of Earth (and it's pointed in our direction), that's absolutely true, but it doesn't apply to pulsars.

In future news...

[iamapizza]

... we'll discover yet another class of pulsars, known as category WEB20, which emit purely Beta rays. And they reflect stuff!

Re:It's all supposition

[qeveren]

The equator of something like this is only moving at around 200km/s, what's unreasonable about that?

Would the Physicists Please Stand Up

[HungSoLow]

Assuming a Neutron star is actually solely made up of Neutrons ... how does it emit electromagnetic radiation when there's no charged particles? Is it just the minute amount of charged particles that reside that emit the radiation, or is it perhaps charged particles around the star, orbiting violently that emit?

Re:Would the Physicists Please Stand Up

[Gil-galad55]

The neutron star surface does emit thermal X-rays because it is hot. However, the electromagnetic radiation originates outside the neutron star, in its magnetosphere.

Pulsars have extremely strong magnetic fields and rotate anywhere from 1-to-1000 times a second. Just like an electric generator, this produces huge electromagnetic fields, and these accelerate electrons to very high energies indeed. These electrons than bang into photons and give them a large chunk of energy in a process called inverse Compton scattering, and we get gamma rays.

(This is the so-called leptonic channel; it is also possible some gamma rays are produced via pions, but the origin of the energy is the same: the huge electromagnetic fields generated by this spinning magnetic dipole.)

Re:Would the Physicists Please Stand Up

[HungSoLow]

But I still don't see how neutral matter can produce radiation? Thermal radiation occurs because of electrons jumping between energy levels, but in an all neutron soup, there's no jumping (none that I can imagine). Moreover, how can neutron matter produce a magnetic field (I'm probably just missing some known mechanism)? I can see that charged matter interacting with the magnetic field produces radiation (just like the northern/southern lights) but my question is where does that field come from? Is there perhaps a neutron --> proton + electron --> neutron reactions that occur on a regular basis with radiation being a byproduct?

Re:Would the Physicists Please Stand Up

[HungSoLow]

Sorry about replying to my own comment:

Wikipedia - Neutron Star

"On the basis of current models, the matter at the surface of a neutron star is composed of ordinary atomic nuclei as well as electrons."

It seems as one moves deeper into the star, the more it becomes a pure sea of neutrons. So all the charged matter on the surface, rotating around like crazy, creates the magnetic field which then causes the emission of radiation.

Re:Would the Physicists Please Stand Up

[PPH]

Perhaps, a better question would be: Does the thermal radiation emitted from a neutron star originate from the neutrons themselves? If so, through what mechanism? Or is this radiation emitted by the star's surrounding atmosphere (gas cloud) interacting with the star's spinning magnetic field?

Neutrons, by themselves, do have a magnetic moment.

Re:Would the Physicists Please Stand Up

[niklask]

But I still don't see how neutral matter can produce radiation? Thermal radiation occurs because of electrons jumping between energy levels

Thermal radiation is solely due to the fact that the object has a temperature. Planck's law describes the spectrum of the radiation emitted by a black body.

but in an all neutron soup, there's no jumping (none that I can imagine). Moreover, how can neutron matter produce a magnetic field (I'm probably just missing some known mechanism)?

Indeed. See below.

I can see that charged matter interacting with the magnetic field produces radiation (just like the northern/southern lights) but my question is where does that field come from? Is there perhaps a neutron --> proton + electron --> neutron reactions that occur on a regular basis with radiation being a byproduct?

Yes. As you found out yourself, a neutron star is not perfect. There is always a small percentage of protons and electrons, mostly in the surface crust. As the neutron star is rapidly spinning, this creates a strong magnetic field.

Re:Would the Physicists Please Stand Up

[gatkinso]

Matter falling onto the stars surface, getting all combobulated, and the resulting radiation from the combobulation shot out at the magnetic poles (which are rotating on a different axis than the star iself) is basically how I remember it from long ago.

Admittedly, some minor details are being glossed over.

But actually, "combobulated" is not a bad summary of the series of lectures in a long ago Astronomy 201 class that covered pulsars.

Re:Would the Physicists Please Stand Up

[gatkinso]

From what I remember from a sophmore astronomy class, the matter inside the neutron stars is a liquid mixture of neutrons as well as electrons, is a superconductor, and is spinning around at an incredible rate - thus producing the immense magnetic field.

Well, atleast this is what some brainy f-ers theorized. Who knows. All I know for sure is that I was a math major, and took that class because I thought it would be easy. Such a fool in my youth.

Re:Would the Physicists Please Stand Up

[gatkinso]

The star was very hot (as you might imagine) when it collapsed after the super nova event. Not massive enough to form a black hole, the very very dense neutron matter stopped the collapse. All protrons and most electrons (a 1-1 relationship) were squeezed into neutrons forming a solid crust, a liquid "mantle" of neutrons and electrons, and possibly a solid core, but no one really knows what the interior is like.)

The resultant body is very small - about the same diameter as the Washington DC beltway. It is still hot as fuck (you think?). However it is also very small, with the following results: 1) it will take a long time for the heat to radiate away from such a small surface area, and 2) conserving angular momentum, it started to spin really really fast.

With the resultant spin, a gigantor magnetic field is produced.

The gravity of this object is very strong - a feather dropped onto it from 1 AU will produce the same amount of energy as an exploding 3 megaton nuclear warhead when it hits the surface. Some of this radiation and shit gets channelled away from the object from the poles. Since the thing is spiining and wobbling, occaisionally one of these poles point toward earth... then away... then back... sweeping the beam of particles and shit produced by matter falling on the surface across our radio telescopes... producing the pulsing effect that gives it it's name.

The period of these events is very small. Like I said, that f-er is spinning fast as shit.

That is what I remember, anyway. Most of that is probably wrong. Sigh. I am getting old.

Re:Would the Physicists Please Stand Up

[The_Wilschon]

A gas of neutrinos, no matter how hot, should not emit blackbody radiation simply because neutrinos do not couple to photons. Oh, they do indirectly (through a W or some such), but that's gonna be a much higher order process and not particularly significant.

Re:Would the Physicists Please Stand Up

[gatkinso]

It is the electrons that make it a superconductor. They are floating around in that neuton degenerate liquid doing fuck knows what, and even of the pressure and gravity were not enough to trap them, the mile or so thick solid crust would.

Re:Would the Physicists Please Stand Up

[gatkinso]

Solid crust is mainly iron and cobolt nuclei packed together at electron degenerate densities.

It is wascky - wiki it for yourself... or better yet crack an intro to Astronomy text. It is pretty intense.

And while I don;t doubt that I have misstated things, I have painted a fairly accurate picture with very broad strokes.

Re:Would the Physicists Please Stand Up

[gatkinso]

Nope - the gravity is too strong. Gravity is very wimpy when dealing with low mass - say like the mass of the earth, but exceed the Chandrasekhar limit of mass an all of a sudden gravity becomes more powerful than ANY known force.

So powerful that at about pi * Chandrasekhar light itself cannot escape.

Quiz - why iron (and a bit of cobalt)? Hint: carbon, nitrogen, oxygen.

It is my personal belief that there is no other force other than gravity, and that when God/god/gods/G-d/ad mauseum created the universe all s/he/it did was create gravity, and disturb it.

Re:Gamma ray bursts and extinction events?

[ceoyoyo]

I've found that gamma rays aren't the least bit discreet. They either make things disintegrate or turn people into man-spider hybrids.

Re:It's all supposition

[ceoyoyo]

You'll find if you figure out how much circular momentum there is in a star, it would be very, very odd if neutron stars were NOT spinning that fast.

Of course a flat statement of unsubstantiated "fact" is the beginning of all good scientific statements.

Re:and it's pulsing

[LVSlushdat]

Your wish is NOT my command, Comrade UncleWilly...

Re:I got a C in

[Chris Burke]

Yeah, but no employer, even for a quantum mechanics related job, wants to hear that you may or may not have graduated with a degree.

Its proximity to earth is a good thing!

[unassimilatible]

The pulsar, which formed in a supernova explosion about 10,000 years ago, emits 1,000 times the energy of our sun.

1. ??
2. Capture energy with solar panels
3. Profit

Re:Its proximity to earth is a good thing!

[Gil-galad55]

Sorry, its high luminosity is more than offset by its distance of kiloparsecs. The relevant quantity is flux, which goes like luminosity/distance^2.

Name it the Al Gore Pulsar

[Nom du Keyboard]

The pulsar, which formed in a supernova explosion about 10,000 years ago, emits 1,000 times the energy of our sun.

Talk about Global Warming!

Re:and it's pulsing

[rossdee]

Its 4600 light years away. If there was intelligent life there, they are just finding out who won the trojan war, they don't know about Barack Obama yet.

Actually that is what they thought at first

[gatkinso]

They thought is was a signal from another civilization, and they called pulsars LGM's (for Little Green men).

That is a true story!

Re:I got a C in

[InfiniteLoopCounter]

Quantum mechanics you insensitive prick!

That's because you forgot to observe that all the other students added in an extra box to the true or false and multiple choice sections.

Next time you too might want to add in "true and/or false", d.) "some possible combination of (a), (b), and (c)." to all these questions.

Re:Gamma ray bursts and extinction events?

[ceoyoyo]

Whoops, I knew it was one or the other. The basic thesis is sound though - a giant green guy with an anger management problem is even LESS discreet.

Re:Puny Humans

[Whiteox]

I suggest we all go selectively breed and send our offspring to face trials of horrors.

Could we send the telephone sanitizers first?

Re:Gamma ray bursts and extinction events?

[Whiteox]

Earth vs the Spider is the more thoughtful movie.
http://www.imdb.com/title/tt0282178/

Re:Gamma ray bursts and extinction events?

[techno-vampire]

Kids today. They don't even understand any more that gamma rays only have an effect on man-in-the-moon marigolds.

Re:I got a C in

[omuls are tasty]

Clearly you've never sought work at Schroedinger's Pet Store.

Re:Gamma ray bursts and extinction events?

[hesaigo999ca]

Or give them green eyes, and make them lift cars over their heads.

To be that hot, what is it made of?

[misterjava66]

To be that hot, that it only shines in gamma, what could it be made of?
Obviously it is some form of degenrate matter, but can a quark-star get that hot?
Does this level of heat, require a size so small that a quark-star is not suffiecient?

Just wondering, does anyone have a calc as to how hot something realatively-big like
a nuetron star should be vs. how hot something much smaller like a quark-star should
be? Can we measure the size of the beam source by some means?

Re:To be that hot, what is it made of?

[niklask]

To be that hot, that it only shines in gamma, what could it be made of? Obviously it is some form of degenrate matter, but can a quark-star get that hot? Does this level of heat, require a size so small that a quark-star is not suffiecient?

Just wondering, does anyone have a calc as to how hot something realatively-big like a nuetron star should be vs. how hot something much smaller like a quark-star should be? Can we measure the size of the beam source by some means?

Why do you assume that the gamma-ray radiation is thermal, which it in fact is not.

Re:Gamma ray bursts and extinction events?

[AliasMarlowe]

Should we hide in our basements, crack our neighbour's heads open and feast on the goo inside?

I am interested in your ideas and wish to subscribe to your newsletter.

Pulsars accelerate ions to high energy levels due

[mmell]

to incredibly high magnetic fields combined with high rotational velocities . . .

So . . . has any pulsar ever been gobbled up by a microscopic black hole, or turned into strange matter (stranglets), or caused a quantum vacuum explosion? No?

GO CERN!

Re:and it's pulsing

[OrangeTide]

We gotta do what the TV tells us. It says it's a message of hope. I'm not sure what to hope for, but we're all real hopeful.

Do we need to have a President every 4 years? Can't we take a vacation once in a while?