Thread: Accretion theory is OUT for Supernovas

Origin of key cosmic explosions unraveled.

Using NASA's Chandra X-ray Observatory, Gilfanov and his team studied the supernovas in five nearby elliptical galaxies and the central region of the Andromeda galaxy.

"Our results suggest the supernovae in the galaxies we studied almost all come from two white dwarfs merging," said co-author Akos Bogdan, also of Max Planck.

"If the supernova were produced by accretion, the galaxies would be roughly 50 times brighter in x-rays than actually observed."

Evidently, accretion allows for a slow, steady buildup of matter whereby the initial spark really is caused by gravitational compression of matter. Collisions, on the other hand, result from much lower masses, and I would suspect tend to produce a much "dirtier", though undoubtedly more spectacular, supernova explosion.

[I]Evidently, accretion allows for a slow, steady buildup of matter whereby the initial spark really is caused by gravitational compression of matter. Collisions, on the other hand, result from much lower masses, and I would suspect tend to produce a much "dirtier", though undoubtedly more spectacular, supernova explosion.[/I]

I've read the article and the news blurb from the Chandra site.
It seems that these 'mergers' are between two white dwarfs, and trigger Type Ia supernovas. It looks like the data is from elliptical galaxies only. It makes sense that mergers could trigger such events. However, it also seems, on the face of it, that such mergers ought to be pretty rare compared to, say, accretion events in binary/multiple systems of white dwarfs in tight orbits . I would have thought accretion to be a more common mechanism... is there a flaw in my reasoning? hmm...

Would this affect the use of Type Ia supernovas as standard candles?

Originally Posted by tom

Would this affect the use of Type Ia supernovas as standard candles?

Yes. They quote astronomer Mario Livio as saying "Knowing how supernovas are formed is key to better understand how they can be used to measure cosmic distances"

It turns out that there is a correlation between the Absolute Magnitudes of Type Ia supernovae and their 'light-curves' or plots of light intensity vs. time.
The light curve reveals the luminosity and the luminosity (Absolute Magnitude) allows a calculation of the distance. It sounds as though Livio is saying that a better understanding of the mechanism of SNIa formation will allow better theoretical models of SNIa light curves and thus more a accurate cosmic distance scale. This would mean a more accurate measure of cosmic expansion, and tighter constraints on Dark Matter and Dark Energy models since these are tied to the expansion rate.

Oops... the article does say that these events occur in binary systems of white dwarfs rather than random collisions. That makes much more sense!

Originally Posted by tom

Would this affect the use of Type Ia supernovas as standard candles?

Yes. They quote astronomer Mario Livio as saying "Knowing how supernovas are formed is key to better understand how they can be used to measure cosmic distances"

It turns out that there is a correlation between the Absolute Magnitudes of Type Ia supernovae and their 'light-curves' or plots of light intensity vs. time.
The light curve reveals the luminosity and the luminosity (Absolute Magnitude) allows a calculation of the distance. It sounds as though Livio is saying that a better understanding of the mechanism of SNIa formation will allow better theoretical models of their light curves and thus more a accurate cosmic distance scale. This would mean a more accurate Hubble constant, and tighter constraints on Dark Matter and Dark Energy models.