miércoles, 2 de noviembre de 2011

Astrophysics - Elusive Preon Stars --Do They Exist?


A preon star is a proposed type of compact star made of preons, a group of hypothetical subatomic particles that could originate from supernova explosions or the Big Bang. Preons were originally proposed as quark constituents over three decades ago, but in 2005, Fredrik Sandin and Johan Hansson of the Luleå University of Technology in Sweden came up with the concept of preon "stars" or "nuggets" in space.
These objects, would be somewhere between the size of a pea and a football, with a mass comparable to the Moon with a density that would be in the range between a neutron star--the densest ordinary form of matter--and a black hole.

There was a time when discovering a new particle would win you the Nobel prize - these days you get a $50 gift voucher and told to stop causing trouble.  The Greeks figured that the smallest possible unit was the atom - named for their word for 'uncuttable'.  This got cut up into a nucleus and orbiting electrons, then we smashed the nucleus up into nucleons (protons and neutrons), the electron into leptons, and just because there weren't quite enough different colours on the "Sub-atomic particles chart" yet we figured out how to break the nucleons and other hadrons into quarks.

So it was combination of excitement and a muttered sigh of "again?" that greeted the predictions of researchers of Luleå University of Sweden in 2007.  Fredrik Sandin and Johan Hansson support the idea that quarks themselves (previous holders of "that's it, these are the smallest pieces for real this time" award) are in fact made up of smaller preon particles. 

Preon models have been popular as early as the 1980s, after which they lost ground against the scientifically-sexier superstring suppositions.  Twenty years later and with no pesky 'validation' in sight, it seems that people are once again interested in proving the preon.

And what proofs they've postulated.  Normally a scientist designing an experiment to detect a tiny sub-sub-atomic structure finds themselves saying thing like "I think there's this utterly insanely tiny thing that's never been directly observed in any form, so to prove it I'd like you to hollow out a mountain for me and fill it with carefully prepared chemicals". 
Luckily for scientists swimming against the string-tide, the proof of their theory wouldn't be quite so costly. They postulate that isolated clumps of preon matter created during the Big Bang may have remained stable, rather than following the preon-quark-hadron-atom-molecule-solid-iphone(or whatever) condensation that most of the material did.

These hyper-dense chunks of primordial preons would still be shooting about the cosmos creating effects we could easily observe.  These effects include bending light, creating gravity waves and drilling lines of seismic shocks through the Earth's crust - so if you can detect those, you've either foundpreons or are being attacked by the X-Men.  
More importantly such seismic signatures could conceivably be detected in the wealth of seismic data already being recorded worldwide - and the gravity waves would be of a frequency detectable by table-top devices rather than the "Bond Villain Lair" scale such equipment normally demands.

Observation is the only route available to the enthusiastic particle master ("gotta detect 'em all!")  While other sub-hadron units can be briefly observed with a few miles of accelerator and enough power to light up a city - don't try this at home - the only way to produce preons would be to recreate the conditions of the Big Bang.
Nine out of ten Mad Scientists agree that while that would be the most awesome experiment ever, the only people who'd get useful data out of it would be whoever evolved to sentience in the newly created universe. The team believed preon nuggets could have been created in the early moments of the universe and lingered as a form of dark matter that primarily interacts with normal matter though gravity.

Fredrik and Johan have already worked out a system whereby a trio of preons could combine to construct all the quarks already observed.  The math is ready, the idea is interesting, and all they're missing is some experimental verification.  Just like all the other theories we have in that field - but with verifiable tests ready to go, even being proved wrong would be a useful result for everyone.

Source: The Daily Galaxy via nature.com - focus.aps.org

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