The headline here is a bit of an overstatement. Nothing in the original paper is casting doubt on Type Ia supernovae as reliable standard candles. It is definitely an embarrassment that we still don't know the mechanism by which Sne Ia occur, but empirically their luminosities can be calibrated well enough that the accelerating expansion of the universe is not in doubt. However, to determine the nature of dark energy (specifically, its equation of state), it may be necessary to calibrate SN Ia luminosities better, and that will probably require understanding exactly what they are.
There are two major SN Ia models: the double degenerate, which involves two white dwarfs colliding, and the single degenerate, which involves one white dwarf accreting matter from a regular star. There have been two approaches to distinguishing between the two models. One is to look for hydrogen in the spectrum a long time after the supernova. In the single degenerate model the supernova shock will strip hydrogen from the companion star's atmosphere, but in the double degenerate model, there will be no hydrogen to strip.
The other method is to look at the very early light curve of the supernova, as this paper did. The early light is expected to rise in a straight line as the surface area of the shock expands. A deviation from this straight line, particularly in the blue bands, then could indicate some interaction between the shock and a companion. This paper found such a "blue bump" in the early light curve of a recent supernova. (There has been at least one earlier paper that also found a blue bump in another supernova.)
I'm out of the field now, so my knowledge isn't quite up to date, but my impression is that the observational evidence may be pointing to a mix between the two mechanisms. For anyone interested, I wrote a little bit about this problem here:
How would you explain, to a layman, why standard candles--phenomena we must measure from great distances--are trusted to be as consistent as well believe them to be?
I always hate it when an article drops that we've "proven the existence of dark matter". We've done no such thing. Usually that sentence describes some of the proof of the fact that our matter and energy predictions are off by an order of magnitude... Proof of the problem that dark matter/energy theories attempt to resolve. I know it's a nitpick, but it drives me nuts.
The article says we've proven the existence of dark energy, not dark matter. They're not the same thing.
That said, if it does turn out that the SN1a "standard candle" scale has to be revised, that might impact the finding of accelerated expansion on which the dark energy model is based. It will be interesting to see how other cosmologists respond to this paper.
"proven the existence of dark matter," to me, says that we've proven that there's a thing with some known properties that needs a lot more explaining. And that's the actual intent of the people who are saying it, too.
Same thing with dark energy, although even fewer of the properties of dark energy are known.
It is interesting that those who are looking experimentally for both dark matter and dark energy have come up empty in every experiment so far performed.
The theorists seem to ignore this and rely more on faith in their mathematical theories and models leading to dogmatic reliance on their belief not on experimental evidence.
Reminds me of the "The Neverending Debate" between String Theorists and Non-String Theorists.
Mathematics is a very useful tool, but if reality differs from the mathematic model then the mathematics is not sufficient and is only a simplistic view for us to use.
[+] [-] antognini|8 years ago|reply
There are two major SN Ia models: the double degenerate, which involves two white dwarfs colliding, and the single degenerate, which involves one white dwarf accreting matter from a regular star. There have been two approaches to distinguishing between the two models. One is to look for hydrogen in the spectrum a long time after the supernova. In the single degenerate model the supernova shock will strip hydrogen from the companion star's atmosphere, but in the double degenerate model, there will be no hydrogen to strip.
The other method is to look at the very early light curve of the supernova, as this paper did. The early light is expected to rise in a straight line as the surface area of the shock expands. A deviation from this straight line, particularly in the blue bands, then could indicate some interaction between the shock and a companion. This paper found such a "blue bump" in the early light curve of a recent supernova. (There has been at least one earlier paper that also found a blue bump in another supernova.)
I'm out of the field now, so my knowledge isn't quite up to date, but my impression is that the observational evidence may be pointing to a mix between the two mechanisms. For anyone interested, I wrote a little bit about this problem here:
https://joe-antognini.github.io/astronomy/typeia-progenitors
[+] [-] JumpCrisscross|8 years ago|reply
[+] [-] ohthehugemanate|8 years ago|reply
[+] [-] pdonis|8 years ago|reply
The article says we've proven the existence of dark energy, not dark matter. They're not the same thing.
That said, if it does turn out that the SN1a "standard candle" scale has to be revised, that might impact the finding of accelerated expansion on which the dark energy model is based. It will be interesting to see how other cosmologists respond to this paper.
[+] [-] greglindahl|8 years ago|reply
Same thing with dark energy, although even fewer of the properties of dark energy are known.
[+] [-] oldandtired|8 years ago|reply
The theorists seem to ignore this and rely more on faith in their mathematical theories and models leading to dogmatic reliance on their belief not on experimental evidence.
Reminds me of the "The Neverending Debate" between String Theorists and Non-String Theorists.
Mathematics is a very useful tool, but if reality differs from the mathematic model then the mathematics is not sufficient and is only a simplistic view for us to use.