Mysterious pulsar with hidden powers discovered

Oct 14, 2010
Illustration: NASA/CXC/M.Weiss

Dramatic flares and bursts of energy - activity previously thought reserved for only the strongest magnetized pulsars - has been observed emanating from a weakly magnetised, slowly rotating pulsar. The international team of astrophysicists who made the discovery believe that the source of the pulsar's power may be hidden deep within its surface.

Pulsars, or , are the collapsed remains of . Although they are on average only about 30km in diameter, they have hugely powerful surface magnetic fields, billions of times that of our Sun.

The most extreme kind of pulsars have a surface 50-1000 times stronger than normal and emit powerful flares of gamma rays and X-rays. Named magnetars (which stands for "magnetic stars") by astronomers, their huge magnetic fields are thought to be the ultimate source of power for the bursts of .

Theoretical studies indicate that in magnetars the internal field is actually stronger than the surface field, a property which can deform the crust and propagate outwards. The decay of the magnetic field leads to the production of steady and bursting X-ray emission through the heating of the neutron star crust or the acceleration of particles.

Now, research published today in , suggests that the same power source can also work for weaker, non-magnetar, pulsars. The observations, which were made by NASA's Chandra and Swift X-ray observatories of the neutron star SGR 0418, may indicate the presence of a huge internal magnetic field in these seemingly less powerful pulsars, which is not matched by their surface magnetic field.

"We have now discovered bursts and flares, i.e. magnetar-like activity, from a new whose magnetic field is very low," said Dr Silvia Zane, from UCL's (University College London) Mullard Space Science Laboratory, and an author of the research.

Pulsars are highly magnetized, and as they rotate winds of high-energy particles carry energy away from the star, causing the rotation rate of the star to gradually decrease. What sets SGR 0418 apart from similar neutron stars is that, unlike those stars that are observed to be gradually rotating more slowly, careful monitoring of SGR 0418 over a span of 490 days has revealed no evidence that its rotation is decreasing.

"It is the very first time this has been observed and the discovery poses the question of where the powering mechanism is in this case. At this point, we are also interested in how many of the other normal, low field neutron stars that populate the galaxy can at some point wake up and manifest themselves as a flaring source," said Dr Zane.

A crucial question is how large an imbalance can be maintained between the surface and interior magnetic fields. SGR 0418 represents an important test case.

"If further observations by Chandra and other satellites push the surface magnetic field limit lower, then theorists may have to dig deeper for an explanation of this enigmatic object," said Dr Nanda Rea, Institut de Ciencies de l'Espai (ICE-CSIC, IEEC) in Barcelona, who led the discovery.

Explore further: POLARBEAR detects curls in the universe's oldest light

More information: 'A low-magnetic-field Soft Gamma Repeater' is published in the 14 October issue of Science Express.

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User comments : 3

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4.8 / 5 (6) Oct 14, 2010
Its only going to get stranger and stranger.
3 / 5 (2) Oct 15, 2010
Jeez, you would almost like to say:
"Maybe it has something to do with neutron decay... etc". But then again, I don't know the official publications by heart.
My apologies if I offended anyone.
1.4 / 5 (5) Oct 17, 2010
Its only going to get stranger and stranger. . . .

Until astrophysicists read the papers already published on neutron repulsion [1-5] or study nuclear rest mass data and rediscover this empirical fact themselves.

1. "Attraction and repulsion of nucleons: Sources of stellar energy", Journal of Fusion Energy 19, 93-98 (2001).

2. "Nuclear systematics: III. The source of solar luminosity", Journal of Radioanalytical & Nuclear Chemistry 252, 3-7 (2002).

3. "Super-fluidity in the solar interior: Implications for solar eruptions and climate", Journal of Fusion Energy 21, 193-198 (2002).

4. "Neutron repulsion confirmed as energy source", Journal of Fusion Energy 20, 197-201 (2003).

5. "Composition of the solar interior: Information from isotope ratios", Proceedings SOHO/GONG Conference on Helioseismology (ESA SP-517, editor: Huguette Lacoste, 2003) 345-348.

Oliver K. Manuel
Former NASA Principal
Investigator for Apollo