I saw this story referenced yesterday, but I didn’t have the time to post a note about it:
“Astronomers used to believe that all Type 1a supernovae were essentially the same brightness. That’s because they explode with the same amount of fuel. But now a supernova has been discovered that’s twice as bright as all the other Type 1a supernovae. This is a problem, since this kind of supernovae are used as standard candles, to determine distances across the Universe. Most recently, these supernovae have been used to calculate the mysterious force called dark energy that seems to be accelerating the expansion of the Universe.”
What they mean by standard candle is that if each of these Type 1a Supernovas were exactly the same size and made out of the same material (as is predicted by the up-to-now commonly accepted Chandrasekhar limit, which says that the largest a white dwarf star, which are made up of degenerate matter, can grow is only 1.4 solar masses or so) then you would expect that when these identical objects explode, the explosions would be about the same size too.
These observations indicate that we may have put too much trust in the Chandrasekhar limit as an absolute boundary. If that’s the case, astrophysicists are going to have revisit their understanding of degenerate matter, and this possibly throws the whole issue of dark energy into doubt. (Dark Energy is thought to be the cause of the apparently observed outward acceleration of matter at the edge of the visible Universe.)
There’s plenty of information about any of these topics on Wikipedia if you’re looking for more background.
Read the rest here: New Kind of Supernova Discovered
(Via Universe Today.)
So let me get this right. We’re calibrating the Hubble relationship between distance and red shift (i.e recession speed). If some type 1as are brighter, then they are actually further then we assume and that has implications for the question of whether the expansion is accellerating. But I can’t figure out if this new information implies a slower rate of acceleration (or could eliminate it entirely) are a faster rate. It seems to me that this would reduce the acceleration.
That’s how I’d read it as well. If they’re brighter than expected, that would put them further away. If they’re further away then the observed doppler shift derived recessional velocity would be less – and the Hubble relationship chart would plot them closer to a straight-line fit.
This doesn’t preclude dark matter – but would seem to raise questions about non-zero cosmological constant that’s been resurrected of late to explain the apparent anomolous acceleration.
I’m not sure what other effects are supposed to be driven by dark energy, but I wonder if they can be explained away as well.
Frankly I’m more interested in the fact that the Chadrasekhar limit is being violated. That was a pretty well accepted idea…
Well there’s an awful lot we don’t know about the behavior of matter under these extremes of temperature and pressure. We believe there are stable islands when the ratio of neutrons to protons are at appropriate values. The entire core of the star may be able to enter some kind of a stable or “crystalline” state if the balance between protons and neutrons is appropriate which might require more totasl mass to overcome. I have no idea how we would generate the necessary temperatures and pressures and relative proton/neutron ratios in order to test such speculation.