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Fraser
2009-Dec-03, 04:30 AM
The supernova 2007bi wasn't your typical supernova: it was 10 times brighter than a Type Ia supernova, making it one of the most energetic supernova events ever recorded. Astronomers from the University of California Berkeley have analyzed the explosion, which was recorded by a robotic survey in 2007, and found that it is likely the [...]

More... (http://www.universetoday.com/2009/12/02/superbright-supernova-first-observed-of-antimatter-variety/)

Jerry
2009-Dec-03, 06:15 PM
I have major heartburn with the science behind this article. This was a MAJOR bright event observed in a 'nearby dwarf galaxy'. The article also points out that dwarf galaxies are anything but rare. So why would we find the first of this type of event in a nearby galaxy? We have seen many supernova events at much, much greater distances - selection effects - the ability to see brighter objects at greater distances - demand that the most distant events we happen to record are the brightest, even if they are rare locally. Is this supernova really that unique? Or is the calculated magnitude of the most distant events we observe severely underestimated?

Check out this article, new in archives today: arXiv:0912.0263

SN 2006bt: A Perplexing, Troublesome, and Possibly Misleading Type Ia Supernova


SN 2006bt displays characteristics unlike those of any other known Type Ia supernova (SN Ia). We present optical light curves and spectra of SN 2006bt which demonstrate the peculiar nature of this object. SN 2006bt has broad, slowly declining light curves indicative of a hot, high-luminosity SN, but lacks a prominent second maximum in the i band as do low-luminosity SNe Ia...

...SNe Ia have been very successfully modeled as a one-parameter family, and this is fundamental to their use as cosmological distance indicators. SN 2006bt is a challenge to that picture, yet its relatively normal light curves allowed SN 2006bt to be included in cosmological analyses.

"successfully modeled" Is a statement of optimisim, not fact. So is this:


We generate mock SN Ia datasets which indicate that contamination by similar objects will both increase the scatter of a SN Ia Hubble diagram and systematically bias measurements of cosmological parameters. However, spectra and rest-frame i-band light curves should provide a definitive way to identify and eliminate such objects.

The simple fact is type Ia supernovae are a fairly broad class of events that are not completely understood. It is not a fact that if you pick a sample of events that have the most consistent spectra and light curves, that you can safely assume that you have accounted for every parameter necessary to pinpoint the magnitude; and using this information you can then confidently predict the magnitude of the most distant events.

The most distant events, necessary for cosmological studies, will always have the highest signal-to-noise ratios and the poorest rest-frame spectrometrics, making them the most difficult to properly characterize. Before assigning any cosmology, you should assume the distant sample is dominated by over-magnitude events and then work backwards. This is opposite from, and in stark contrast to, the techniques and overly optomistic assumptions made by Foley. Everytime -everytime we see a near-local supernova lightcurve that exceeds the predefined limits for supernova type Ia magnitudes, it corralled off and excluded from the baseline sample. This process ignores the implications these local, over-brilliant events have upon gross assumptions made about the brilliance of the most distant events we observe. It is bad science.

dgavin
2009-Dec-03, 09:33 PM
I have major heartburn with the science behind this article. .......

.....It is bad science.

Jerry I think you missed the entire point of the article. It's not about the discovery of a "one of a kind" event. But the first object discovered that is Possible evidence for long suspected Pair-Instability Nova.

Pair-Instability Nova (Chain Reactions) are a consequence of Nuclear Thermodynamics and has been theorized for a while, but there has not been proof of this sort of reaction happening naturally before.

This now gives us an example where some Super or Hyper-nova's, might be a consequences of Pair-Instability reactions. It would take many more observations of similar objects to confirm such a correlation, but this object is the first in the proof of such a thing. Just because it's a first, doesn't make it One of a Kind. Doesn't mean it should be ignored either.

Kwalish Kid
2009-Dec-03, 10:24 PM
The simple fact is type Ia supernovae are a fairly broad class of events that are not completely understood. It is not a fact that if you pick a sample of events that have the most consistent spectra and light curves, that you can safely assume that you have accounted for every parameter necessary to pinpoint the magnitude; and using this information you can then confidently predict the magnitude of the most distant events.
Do you have any evidence that this event has spectral characteristics that are anything like a SN Ia?

korjik
2009-Dec-03, 10:30 PM
Not only that, but the reason it was 'discovered' in a nearby galaxy is probably more about it being close enough to be absolutely sure more than anything else.

I can see several articles coming out about how several questionable SN at long distances are now likely to be PIN (Pair Instability Novae)

I also can see Jerry complaing about each one and about how that means all of cosmology is wrong because he knows how it works better than the people who do it for a living.

EricFD
2009-Dec-03, 10:43 PM
This article kind of brings to mind the hypothetical population III stars that may have inhabited the early universe, which consisted of basically nothing more than hydrogen and helium. It makes sense that these types of supernovae would most likely be found in dwarf galaxies which are low in metallicity and rich in hydrogen and helium content. Quite a remarkable discovery.

Eric