Dramatic news from the world of astro-boffinry today as two theories go head to head in the quest to explain a cosmic explosion of unparallelled power sighted in the skies last Christmas.
This stellar stupendo-explosion was no measly supernova of the sort which may have given rise to the Bible story of the guiding star which guided the Three Kings in to deliver festive presents to the baby Jesus: the flare sighted by NASA's Swift space telescope on Christmas day 2010 was what's known as a Gamma Ray Burst, a sudden monster outpouring of the most savage type of electromagnetic radiation on the entire spectrum. During a GRB, as much energy is pumped out in a few seconds as our Sun will emit in its entire life.
And the Christmas GRB of last year was a belter, one fit to herald the arrival of some astonishing hyper-deity whose radiance could be apparent only to gamma vision like that of the Swift satellite's Burst Alert telescope. Any Oriental royals wishing to pay the notional Gamma Jesus a call would have had to bustle, however, as the Christmas Burst lasted only 28 minutes - but this is in fact a very long time for a GRB, indicating energy release of even more than normal stupendity.
Thus it is that eminent brainboxes of the astrophysical world, astonished at the festive gamma blast results, have toiled for the past year to work out just what kind of stellar cataclysm - what unfeasible cosmic violence - could possibly have generated so vast an outpouring of energy.
One theory, postulated by a team led by top Spanish astro-boffin Christina Thoene, is that a neutron star - one composed of mega-dense collapsed matter composed entirely of neutrons, like a colossal atomic nucleus - was orbiting a monster red giant along Betelgeuse lines, which then (in the fashion of such stars) blew up and expanded to many times its previous size, engulfing the neutron star within itself. This would cause an early preliminary warning blast in which much of the giant would be violently hurled into space, before the neutronium invader then ploughed deep into the crimson giant's vitals, causing both to fuse together and suck themselves down inside their combined event horizon to produce a black hole.
This would naturally result in characteristic particle jets, the signature of a black hole, and these would roar out into the gas expelled during the initial death throes of the red giant, so causing the strange gamma emissions which reached Earth last Christmas.
That theory would fit well if the festive GRB came from far afield, outside our own galaxy. However a rival boffinry crew headed up by Italy's Sergio Campana suggests that in fact the event may have been much closer, just 10,000 or so lightyears off. In that case a much less violent event would suffice to explain it: namely an enormous comet or similar being ripped apart by the terrific tidal stresses engendered by a neutron star's deep gravitational field, and so showering itself on the neutronium surface below to certain and gamma-visible destruction. Apparently an object only half the mass of the dwarf planet Ceres would suffice, and such bodies are thought to be common out in the icy Kuiper Belt beyond the boundaries of the known solar system.
It's not yet known which of the two theories is correct, though scientists are working on it - and in the meantime are highly chuffed to have such interesting data to chew over.
"The beauty of the Christmas burst is that we must invoke two exotic scenarios to explain it, but such rare oddballs will help us advance the field,” said Chryssa Kouveliotou of NASA's Marshall Space Flight Center, who worked on the red giant theory.
Both scenarios are published with full details, hard sums etc in hefty boffinry mag Nature today. There's a layman's digest courtesy of NASA here. ®