Search This Blog

Wednesday, 25 July 2012

Magnets forged in supernova.....

How's my blogging? Leave some feedback, I get better at this, you get a better read!

I love magnets. A great time waster is to make up some ferrofluid [1], get a nice strong rare earth magnet [2], and just muck about.

Video above: These things, made using elctromagnets, are called Morpho towers [3]. Video courtesy of  Sachiko Kodama.

But sometimes the universe takes things a bit far.

A perfect example of this is the magnetar [4]: a rare type of neutron star [5]. Neutron stars take the word 'extreme' and run with it anyway. Born in the supernova deaths of the most massive stars in the universe, they are so dense that a pinhead of their matter would outweigh a supertanker. Their surface gravity is a hundred billion times stronger than Earths - strong enough to visibly warp the starlight that passes too close to them. Magnetars add a new trick to the act - the most insanely powerful magnetic fields known to exist.

The magnetic field of Earth is about fifty microtelsas. A good rare earth magnet is about one tesla. The most powerfull magnetic fields [6] created on Earth are around a hundred tesla.

Magnetars field reaches about ten gigateslas. That would erase your credit card at a distance of a hundred thousand kilometres. It would tear you apart - due to the diamagnetism of your bodies water [7] - at a thousand kilometres. The field is so strong [8] it turns the surface of the magnetar into a place, so strange, it's hard to credit they are part of the same universe as Earth. Under the influence of that hurricane field space becomes birefringent [9]. Photons - particles of radiation - perform weird acrobatics. Atoms stretch out tubular - I have no idea what what effect that will have on rules of chemistry, but I'd bet on oddness.

To make these objects even more fun, their unstable: Their internal magnetic field gets twisted up by their own rotation, until the energy it's stored gets released in a massive starquake. Unlike an earthquake, one of the side effects of a magnetars starquake is the release of a massive pulse of gamma rays*.

We've learned to study them: As well as massive gamma ray flares the magnetars field decays away as X-rays, reducing down to the .... frankly still insanely high.......  strength of an ordinary neutron star over tens of thousands of years.

Only twenty or so confirmed magnetars have been found - and now there's a new twist in this tale of warped space time and supernova powered magnets:  A new breed of neutron star, that is 'normal' on the outside, but hides the colossal field of a magnetar on the inside, has been coming to light. Astrophysicist are calling these 'low field magnetars [10]' because their external fields are comparatively weak. But their internal fields are still magnetar strength, and when they star quake X-rays come pouring out of cracks in their crusts.

Video above: A visualisation of how the internal magnetic field, of a low field magnetar, re-aligns. Since all that stored energy has to go somewhere it comes pouring out as X-rays. Video courtesy of ESA.

We have only found two of these hybrids, and one in particular has been scrutinised by...well let's see...NASA’s Rossi X-Ray Timing Explorer, the Chandra X-ray Observatory, ESA’s XMM-Newton, Japan’s Suzaku satellite, as well as the ground-based Gran Telescopio Canarias and the Green Bank Telescope.

From this, you might get the impression astronomers are quite interested in these things.

The reason for all this attention has been that, until April of this year, it was going through a sort of 'slow burn' starquake, giving off X-rays instead of higher energy gamma rays, allowing this weird member of a weird species of object to be studied in detail.

The existence of these hybrids suggests that magnetars may be just a phase that some neutron stars go through. That would mean that many of the neutron stars we know of might be hiding a magnetar like inner core, or might have had phases of magnetar like behaviour in the past. And that adds to their usefulness - by studying neutron stars, even from great distances, we can learn how the laws of physics act under unimaginably extreme conditions, which all adds to our knowledge of how the universe (including things that happen here on Earth) works. Adding the most intense magnetic fields in the galaxy to neutron stars makes for nice icing on the cake.

And it's a good thought -  that some of the most deadly objects in the universe can actually help us to learn about it.....

* What zapped Bruce Banner to turn him into Hulk. Although that doesn't actually work. As far as I know.

List of links:


No comments:

Post a Comment