Slashdot Mirror
Supernova Detonates In Empty Space
mlimber tips a story in New Scientist about a powerful cosmic explosion that has astronomers scratching their heads. It apparently resulted from a supernova detonating in empty space, far from any galaxy. Researchers propose that the exploding star was in the gas trail yanked out of a galaxy when it passed or began merging with another. Quoting the lead author of the study: "Even if the galaxies have stopped forming stars, in the tidal tails you can trigger new episodes of star formation [not to mention detonation]." The research will be published in the Astrophysical Journal.
Perhaps it is a weapons dealer giving a demonstration to a race bent on galactic dominance?
Sun Crusher
I haven't read the article (or the paper it talks about), but since I'm an astronomer, I think I have an idea what the strange thing about this is.
Only massive stars end with a supernova, and massive stars are very short-lived. So generally, while a low mass star like our sun is likely to be found far from where it was born, massive stars usually are only found close to where they were born (since they don't live long enough to travel far). But, stars are usually born in dense areas in galaxies (so the space between galaxies would be a very unlikely place for star formation to happen).
So that is most likely why this is considered an odd case.
As clearly stated in the article, this was not a supernova (SN), but rather a gamma ray burst (GRB). The network of satellites referred to all trigger on high energy gamma rays, and look for the afterglow of the event which caused the trigger. The time scale of GRBs is typically on the order of seconds. Core collapse SNe, by comparison, are optically visible and have a brightening and fading timescale on the order of days or tens of days.
Much more is understood of core collapse SNe than the progenitors of GRBs. One of the leading models for short GRB progenitors is the binary inspiral of two massive, compact objects, at least one of them being a neutron star. Obviously we can't resolve the region that the GRB came from, but from the above model, it's inferred that there is a region dense in stars out there, rather than just one isolated star. The second piece of evidence is that the afterglow was actually visible: this afterglow is most likely from shock waves in the interstellar gas, having associated high densities and temperatures, glowing in the optical or xray. If there was no gas by the progenitor of the GRB, there would not have been an afterglow (or the model is wrong).
The slashdot title was therefore wrong in two ways: this was not a SN event, and it was not in empty space - it was just not in a host galaxy.
-Leo
It would only have a red shift if it speeded away from us. If it were coming towards us it would have a blue shift. If it were racing parallel to us, it would have no shift. Nor would there be a comet's tail - the star would explode in a radial fashion with the circle moving parallel to us at relativistic speeds , which would be visible to us as an ellipsis - but it's not fast enough for us to notice the shift, especially from such distances. (and it's too far away to resolve any comet's tail anyway)