Chameleon pulsar baffles astronomers

Jan 24, 2013
Chameleon star baffles astronomers
This illustration shows a pulsar with glowing cones of radiation stemming from its magnetic poles -- a state referred to as "radio-bright" mode. Credit: ESA/ATG medialab

A pulsar that is able, without warning, to dramatically change the way in which it shines has been identified by an international team of astronomers.

Using a satellite X-ray telescope combined with terrestrial the was found to flip on a roughly half-hour timescale between two extreme states; one dominated by X-ray pulses, the other by a highly-organised pattern of radio pulses.

The research was led by Professor Wim Hermsen from The Netherlands Institute for Space Research and the University of Amsterdam and will appear in the journal Science on the 25th January 2013.

Researchers from Jodrell Bank Observatory, as well as institutions around the world, used simultaneous observations with the X-ray satellite XMM-Newton and two radio telescopes; the LOw Frequency Array () in the Netherlands and the Giant Meter Wave Telescope (GMRT) in India to reveal this so far unique behaviour.

Pulsars are small spinning stars that are about the size of a city, around 20 km in diameter. They emit oppositely directed beams of radiation from their . Just like a lighthouse, as the star spins and the beam sweeps repeatedly past the Earth we see a brief flash.

Some pulsars produce radiation across the entire , including at X-ray and . Despite being discovered more than 45 years ago the exact mechanism by which pulsars shine is still unknown.

An international team has made a tantalizing discovery about the way pulsars emit radiation. The emission of X-rays and radio waves by these pulsating neutron stars is able to change dramatically in seconds, simultaneously, in a way that cannot be explained with current theory. It suggests a quick change of the entire magnetosphere. In their research the team combined observations from the X-ray space telescope XMM-Newton and the radio telescope LOFAR (among others). Credit: ASTRON

It has been known for some time that some radio-emitting pulsars flip their behaviour between two (or even more) states, changing the pattern and intensity of their radio pulses. The moment of flip is both unpredictable and sudden. It is also known from satellite-borne telescopes that a handful of radio pulsars can also be detected at X-ray frequencies. However, the X-ray signal is so weak that nothing is known of its variability.

To find out if the X-rays could also flip the scientists studied a particular pulsar called PSR B0943+10, one of the first to be discovered. It has radio pulses which change in form and brightness every few hours with some of the changes happening within about a second.

Dr Ben Stappers from The University of Manchester's School of Physics and Astronomy said: "The behaviour of this pulsar is quite startling, it's as if it has two distinct personalities. As PSR B0943+10 is one of the few pulsars also known to emit X-rays, finding out how this higher energy radiation behaves as the radio changes could provide new insight into the nature of the emission process."

Since the source is a weak X-ray emitter, the team used the most sensitive X-ray telescope in existence, the European Space Agency's XMM-Newton on board a spacecraft orbiting the Earth. The observations took place over six separate sessions of about six hours in duration. To identify the exact moment of flip in the pulsar's radio behaviour the X-ray observations were tracked simultaneously with two of the largest radio telescopes in the world, LOFAR and the GMRT.

What the scientists found was that whilst the X-rays did indeed change their behaviour at the same time as the radio emission, as might have been expected, in the state where the radio signal is strong and organised the X-rays were weak, and when the radio emission switched to weak the X-rays got brighter.

Commenting on the study's findings the project leader Wim Hermsen says: "To our surprise we found that when the brightness of the radio emission halved, the X-ray emission brightened by a factor of two! Furthermore the intense X-rays have a very different character from those in the radio-bright state, since they seem to be thermal in origin and to pulse with the neutron star's rotation period."

Dr Stappers says this is an exciting discovery: "As well as brightening in the X-rays we discovered that the X-ray emission also shows pulses, something not seen when the is bright. This was the opposite of what we had expected. I've likened the changes in the pulsar to a chameleon. Like the animal the star changes in reaction to its environment, such as a change in temperature."

Geoff Wright from the University of Sussex adds: "Our observations strongly suggest that a temporary "hotspot" appears close to the pulsar's magnetic pole which switches on and off with the change of state. But why a pulsar should undergo such dramatic and unpredictable changes is completely unknown."

The next step for the researchers is to look at other objects which have similar behaviour to investigate what happens to the X-ray emission. Later this year there will be another round of simultaneous X-ray and radio observations of a second pulsar. These observations will include the Lovell telescope at Jodrell Bank Observatory.

Explore further: Millisecond pulsars clearly demonstrate that pulsars are neutron stars

More information: Synchronous X-ray and Radio Mode Switches: a Rapid Transformation of the Pulsar Magnetosphere will be published in Science on Thursday 24 January.

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User comments : 25

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Lurker2358
2.4 / 5 (18) Jan 24, 2013
This was the opposite of what we had expected.


Yeah, astrophysicists and material scientists have been getting a lot of that lately.

Bad models make bad predictions. Opposite predictions are about as bad as it gets.
jsdarkdestruction
3.9 / 5 (7) Jan 24, 2013
must be an et communication, eh tuxford?
Q-Star
4.1 / 5 (23) Jan 24, 2013
This was the opposite of what we had expected.


Yeah, astrophysicists and material scientists have been getting a lot of that lately.

Bad models make bad predictions. Opposite predictions are about as bad as it gets.


It's only for the last decade or so that this phenomena have been studied in the detail we have today,,,, being baffled should be expected with any new abilities. With several hundred billions of galaxies, averaging several hundred billions of stars each, I would be baffled if there were NO surprises.

We are collecting more data each year than all previous generations combined and it will take much work and time to make it ALL fit together.
eachus
4.6 / 5 (9) Jan 24, 2013
First don't mistake the confusion and bafflement implied in the article for reality. The physics and/or nuclear chemistry of neutron stars, and in particular their surfaces is almost beyond our current ability to observe and experiment. The two (assumed likely) theories before the observations were that the direction of the beams changed, in which case radio and X-rays would correlate. Or that the stars surface was oscillating between two modes. In that case, which correlates with observations, the total energy radiated by the star's surface should be constant on these time scales, so the X-ray and radio would both fluctuate, but the net energy would stay about the same. Is this the "right" answer?

Don't know, and that is how real science works. You test theories, and throw out those that don't agree with the observations. Then, if necessary create new theories, or refine those that survive several tests without failing.
VendicarD
1 / 5 (4) Jan 24, 2013
Finally we have definitive proof of cold fusion.
Anda
4.3 / 5 (6) Jan 24, 2013
This was the opposite of what we had expected.


Yeah, astrophysicists and material scientists have been getting a lot of that lately.

Bad models make bad predictions. Opposite predictions are about as bad as it gets.


Models are developped according to known data. With new discoveries they evolve.
Don't be so pessimist, we are living in an age of daily new discoveries, and that's exciting.
Oh, that was opposite to your prediction? as bad as it gets...
LarryD
1.8 / 5 (5) Jan 24, 2013
"The behaviour of this pulsar is quite startling, it's as if it has two distinct personalities...'
This comment makes me one if there are in fact two distinct objects but only one being 'radio' visible. Seems unlikely, but could there be something causing a 'rupture' in magnetic fields?
Caliban
5 / 5 (1) Jan 24, 2013
I wonder if this might be evidence of two or more layers of material within the pulsar, rotating at differential velocities, and emitting the observed alternating frequencies. Perhaps continued observation over time will show that they shift in and out of phase?
kevinrtrs
1 / 5 (15) Jan 25, 2013
Don't know, and that is how real science works. You test theories, and throw out those that don't agree with the observations. Then, if necessary create new theories, or refine those that survive several tests without failing.

So many of the new observations contradict the big bang theory; when are they going to throw it out, already?
sennekuyl
4.4 / 5 (7) Jan 25, 2013
When someone comes up with something that explains all the data currently & the new phenomena while making testable claims.

Why bring the BB into this article though?
antialias_physorg
4.6 / 5 (10) Jan 25, 2013
So many of the new observations contradict the big bang theory

It's funny how they don't.
There's only your wish they did. But wishing something doesn't make it true - or your god would have been called into existence by your need for him a long time ago.

Then, if necessary create new theories, or refine those that survive several tests without failing.

And very importantly: Any new theory has to explain the new phenomenon AND all the phenomena the old one explained.
thingumbobesquire
1 / 5 (2) Jan 25, 2013
katesisco
1 / 5 (4) Jan 25, 2013
Wonderful insight -- I read this and thought of two things:
1) that the off/on again regularity of Oklo is now firmly in the camp of nuclear actions, and
2) that we are so imbued with out sun's emissions that if our sun were a neutron star as O Manuel's work suggests, we could not discern it.
rubberman
2 / 5 (4) Jan 25, 2013
I wonder if this might be evidence of two or more layers of material within the pulsar, rotating at differential velocities, and emitting the observed alternating frequencies. Perhaps continued observation over time will show that they shift in and out of phase?


With these bodies there are alot of possiblilities, I was thinking the ultrafast spin combined with the insane magnetism likely causes polarity shifts on the observed intervals (instead of every 11 or 12 years like we see on our sun)...but you may also be on to something Cal.
antialias_physorg
4 / 5 (4) Jan 25, 2013
that if our sun were a neutron star as O Manuel's work suggests, we could not discern it.

It would be quite a bit smaller.
Alternatively if the size were the same, or just the core were a neutron star: Our tides would be quite a bit higher.

With these bodies there are alot of possiblilities, I was thinking the ultrafast spin combined with the insane magnetism likely causes polarity shifts

..or it could just be a pulsar binary (which would be awesone in its own right)
Tuxford
1 / 5 (6) Jan 25, 2013
must be an et communication, eh tuxford?

More likely a galactic navigational beacon. Look up Benford Beacons if you don't like LaViolette's earlier hypothesis.

http://www.astron.../08SETI/

Hey, if you don't think they are here already, you should get out more. I have got family in Argentina who have seen buzzing UFO's off the coast of Mar Del Plata just last fall, for multiple nights. Multiple members have seen several close events over their lifetimes. To discount multiple witnesses so generally reflects badly on the discounter.

Only the US population has been so hypnotized by decades of black budget propaganda. Why? To keep the relativist's dream alive. Dream on Dark. Long live the Huge Bang Fantasy!
Grallen
not rated yet Jan 25, 2013
@antialias: That is exactly what I thought while reading it(Binary pulsars eclipsing each other).
Fleetfoot
5 / 5 (3) Jan 26, 2013
@antialias: That is exactly what I thought while reading it(Binary pulsars eclipsing each other).


It is an obvious thought but the transitions would then be expected to be highly regular.
eachus
1 / 5 (2) Jan 26, 2013
My theory, which might be better thought of as a guess, is this.

Current theories agree that neutron stars to have a very thin crust of normal matter over the neutrons.* If the magnetic fields at the surface are strong enough, some of the neutrons can be brought to the surface, and will "decay" into normal matter emitting X-rays. At other times this upwelling won't quite reach the surface, and the iron and other elements on the surface will absorb the X-rays. But (magnetic) iron getting converted to say nickel, will change its magnetic properties and disturb the magnetic field. Even if it doesn't the kick from the radiation will put energy into the magnetic flux.

So the properties of the surface near the magnetic poles can flip states, either absorbing or emitting X-rays.

*What exists further down is up for grabs. If and when a model for the cores of neutron stars makes testable predictions, or someone figures out how to test current predictions, it may be possible to say more.
Tuxford
1 / 5 (4) Jan 26, 2013
As I understand it, the problem for many of these theories, is that the complex patterns often repeat, change patterns, and repeat, and sometimes stop for a while, and pick up the pattern just where they left off. Sounds like signal processing to me.
RealScience
5 / 5 (5) Jan 26, 2013

So many of the new observations contradict the big bang theory; when are they going to throw it out, already?


@kevin - gosh, that's mighty funny coming from you.
Given how many observations contradict your 6000-year-old-earth theory, when are you going to throw THAT out already?
SteveL
5 / 5 (4) Jan 27, 2013
Hey, if you don't think they are here already, you should get out more. I have got family in Argentina who have seen buzzing UFO's off the coast of Mar Del Plata just last fall, for multiple nights.
UFO just means it's flying and not identified by the viewer. Doesn't have to be, and likely not, aliens.
Some assembly, but no conspiracy required.
SteveL
5 / 5 (4) Jan 27, 2013

So many of the new observations contradict the big bang theory; when are they going to throw it out, already?


@kevin - gosh, that's mighty funny coming from you.
Given how many observations contradict your 6000-year-old-earth theory, when are you going to throw THAT out already?
Man is ignorant and fearful, so man made god in his/her own image. God will exist, for some, so long as ignorant and fearful men and women exist. Some people need something greater than self to lean upon.
SteveL
not rated yet Jan 27, 2013
Back on topic: I didn't see mass mentioned in the article. Could it be as simple as the mass of the pulsar determines whether radio emissions or X-rays are normally emitted? If this pulsar were of borderline mass, it might be seen to switch from one emission to the other. Possibly due to a layering effect such as Caliban described.
Mike_Massen
5 / 5 (5) Jan 27, 2013
kevinrtrs you seem to be a simple thinker with this
So many of the new observations contradict the big bang theory; when are they going to throw it out, already?
I understand your alternative is the world was made in 7 earth days by a deity. So he didn't make it in a flash, which suggests he/she/it is not a god but some loki or being that plays suffering games with all humanity and all of nature because a young girl barely an adult chose a fruit from a tree that was put there and pointed out by that deity or rather lets call it the Prick of "The God of Suffering" & can we please put him back in the dustbin where that idea belongs - we've outgrown the sincere imaginative Moses haven't we ?

Suffice it to say, there is the issue of 'combinatorial complexity', so rather than disparage from the sidelines with ignorance, why dont you stop trying to weave in the creationist aspect on a Science website where discipline is involved with knowledge.

Read: Religion has no discipline !