Supernovae from the earlier times seem to have a higher intrinsic brightness according to this.

You heard it first, here.

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jwj

If you always believe what you already know, you can't learn anything - Liz

that is intersting, i can see how that could be a probelm. but new stars will form from the nebulas made by the supernovaes.

It is interesting to read that overly bright supernova 'type Ia' do not pose a problem for the cosmology derived from distant supernovae, even though they state right in the abstract calibrating these beasts will be problematic.

There is another good (very techinal) paper out that explains how distant supernova are characterized:

http://arxiv.org/PS_cache/arxiv/pdf/...709.4488v1.pdf

DETERMINING THE TYPE, REDSHIFT, AND AGE OF A SUPERNOVA SPECTRUM

Blondin & Tonry

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jwj

If you always believe what you already know, you can't learn anything - Liz

It is not one yet, but before some of us attempt to use this article as fodder for an ATM thread in the astronomy section of the forum it's worth mentioning that in the article, which Fortunate kindly provided us a link to, the authors of the study reported on say the following:

"The findings do not call into question that the universe is accelerating but the evolving mix of supernovae could limit future attempts to determine the nature of dark energy,” said Andrew Howell, lead author of the study and post-doctoral researcher. The paper appears in the Sept. 20 issue of the Astrophysical Journal Letters.

“We found that the early universe supernovae had a higher wattage, but as long as we can figure out the wattage, we should be able to correct for that. Learning more about dark energy is going to take very precise corrections though and we aren’t sure how well we can do that yet.”

Jerry said: "You heard it first, here."

Most reasonable people would agree that this is a pretty bold and pretentious claim. Are you really so sure that you are the first one to think of this? Yet again, Jerry, your confirmation bias shines through--brighter than a supernova--as you immediately latch onto part of the article that fits what you already believe and fail to mention the part of the article that doesn't jive quite as neatly with your worldview.

Jerry seems to equate "we aren't sure" with "we don't know" and conflate that to "anything goes".

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Any day you wake up on "the right side of the dirt" is a good day.

T. Anderson

This paper is more of a "we do know" paper than a "we don't know" paper.

More free hydrogen in the early universe, so not as much had settled into longer-lived small stars. There was more large star formation, so on average, more large supernovas. And the scattered output from a supernova is more likely to form into several small bodies, than another huge one.

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"If this were play'd upon a stage now, I could condemn it as an improbable fiction."
Shakespeare, Twelfth Night
Illuminati's Razor-The most complicatedly evil answer is usually the most correct answer. - Fazor
"Every book is a children's book if the kid can read." - Mitch Hedberg
"Distance doesn’t matter much in space, where if you just start a thing off with the right kind of shove, sooner or later it will get where you want it to go." -Frederik Pohl, Mining the Oort

And we use what to correct the wattage of our best standard candles?

Sorry, any secondary standards, especially conclusions drawn around converging parameters sets based upon cosmological models developed using supernovae data, can only create a sense of false confidence. If attenuation estimates are wrong; if we are only seeing the brightest of supernova events at great distances, there may be an entire population of supernova at cosmic distances with the same magnitude as the local sample; events that we cannot see simply because of environmental dimming.

Look at the data for AGN; quasars - the metallicity in these object at the distances z~0.3 to 3.0 does not evolve measurably. Likewise, mature galaxies are found at these distances with little if any difference in measurable gas and dust.

We will need to look very hard at the observational evidence in the next generation of telescopes to determine whether or not the distant population of supernovae are substantially different from the local population. We also need to learn whether there is a continuum of magnitudes, or a descrete break in the magnitude of supernovae.

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jwj

If you always believe what you already know, you can't learn anything - Liz

VERIFYING THE COSMOLOGICAL UTILITY OF TYPE IA SUPERNOVAE: IMPLICATIONS OF A DISPERSION IN THE ULTRAVIOLET SPECTRA

http://arxiv.org/PS_cache/arxiv/pdf/...710.3896v1.pdf

This paper backpeddles significantly, and contrasts with earlier optomism about the confined nature of supernova type Ia. Supernovae type Ia are just as important as they have always been, but the conclusions drawn from comparisons of the punative local sample and the many events we are now observing at cosmic distances were premature. These issues are not limited to universal expansion and dark energy, but must involve reinvestigation of every theoretical limit and constraint provided by supernova datum.

From the body of the paper:
This is stunning, and Nugent is one of the coauthors.

In English, this says the conclusion drawn 'independently' by Riess and Perlmutter almost a decade ago, that the rate of expansion of the universe is increasing is premature: It is impossible to determine with the data in hand.

And yes you did hear it first, here.

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jwj

If you always believe what you already know, you can't learn anything - Liz

I'm not so sure about your translation.

This takes us out to about 5 billion lightyears, a region within which I expect many of Riess' and Perlmutter's Sne Ia were observed and measured, which led to their conclusion: The universe is expanding at a greater rate today than it was 4 or 5 billion years ago.

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Everyone is entitled to his own opinion, but not his own facts.

To clarify: There are two groups of researchers, the Howell group cited in the first post on this thread found greater-than-expected diversity in distant supernovae and concluded there is evidence of evolution. The Ellis group also found greater diversity in the distant sample, but concluded there is not evidence of evolution in the observed variability of ultraviolet properties – it does not correlate with distance.

Both research groups conclude that the stretch-magnitude relationship is likely still valid. Neither group is throwing supernova science out of the window. Ellis et al. state that they do not have enough local examples of supernovae with ultraviolet light curves to compare the redshifted sample of supernova with in a meaningful way. (It is easier to collect ultraviolet spectra in redshifted space, because it is redshifted into the optical spectrum.) They can only conclude that the ultraviolet light spectrum is more widely varied that they expected, and the UV signature does not vary in ways that are consistent with evolution. Both groups are saying there is something different about redshifted supernova, but noone is sure what.

So what comes next? The Ellis group concludes it is imperative to gather more local ultraviolet data and compare local UV curves with the more distant sample. What is desperately needed is a repair or replacement of the Hubble ultraviolet capability.

I still argue that there should be just as much diversity in the distant sample of supernova events as in the local sample, and insist that the distant sample of supernova ‘type Ia’ are contaminated with what are locally classified as hypernova events. Greater variability in the ultraviolet light curve found in the distant sample is consistent with this argument.

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jwj

If you always believe what you already know, you can't learn anything - Liz

I'm wondering if the extra brightness could be due to applying the Big Bang brightness correction factor (1 + z)^-4 rather than a static universe correction, which could be (1 + z)^-1 or (1 + z)^-2. On this same point, I read an article recently by Disney (in American Scientist), in which he said that the designers of the Hubble telescope did not expect that it would detect stars at the great distances they did. That was the first time I heard that. Of course, they would have been applying the BB correction. Can the extra brightness in the SNe be accounted for this way?

Yes and no. What they are observing in the Ellis study is greater variance in the UV magnitude than is found in the local 'type Ia' templates. Without local guidence, we are in unchartered waters.

The (1+z)^4 correction factor is a relativistic as well as a Big Bang requirement. If the magnitude correction is wrong, it would mean either the redshift is NOT due to expansion, or current relativity theory does not correctly define expansion attenuation, or both. In cases I and III, this would also mean that the time dilation correction is also wrong. The time dilation correction shortens the light curves, and without this correction, the light curves observed at high redshift would be much longer than the local sample. If the lightcurve length/magnitude relationship holds up, this would mean these supernova should be truly brighter!

The net result of such a major miscalculation is difficult to assess, but the best clue might be the fact that far fewer supernovae have been observed at cosmic distances than were expected, based upon the local count. If you assume the supernova population is not really greater in local space, the only realistic conclusion is that the extinction factors are much greater than currently calculated, so these distant supernova are again, truly brighter. This line of reasoning also greatly effects the magnitudes of galaxies, quasars all objects at cosmic distances, and the implications are staggering.

It is important to stress that most supernova researchers currently believe that the magnitude errors are very small in spite of the peculiar high energy lightcurves. What is cool, is that no one really knows, and this type of oddity may portend dramatic shifts of reasoning in the future.

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jwj

If you always believe what you already know, you can't learn anything - Liz

Jerry. Somewhere in my readings over the last few weeks, amidst, moving, closing out my gardens, and setting up my classes, in five different locations....I came across either a paper, or an ArXiv preprint summary....and it said they had found an unexpected source of bias in the distant type1a standard candles....galactic light spillover. Evidently, the surveys of distant galaxies for type 1a candles, and the surveys of less distant galaxies (z's of redshift, not the particles), had been done systemically with the same instrumental slit-width on the telescope. Since a more distant galaxy subtends a smaller angle, it fits into the slit better. The supernova is relatively point-like...and the long exposure spills extra galactic light into the spectrum, reddening it, because of interstellar reddening effects within the host galaxy. (This is not my spiel...I'll hunt for the reference again...I thought I'd find someone here jumping up and down about it). Obviously, it hints that acceleration reddening...or UV spectral anomalies are somehow in cahoots here. Might not be so much dark energy after all. Interesting? Hmm. Pete.

still hunting, but see also, the following....apparently different areas of the same galaxy show different reddening (I'm not even going there)...the authors do. see:http://arxiv.org/PS_cache/arxiv/pdf/...710.4503v1.pdf

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A third rate theory forbids
A second rate theory explains after the fact
A first rate theory predicts...A. Lomonosov

Supernova rates from the Southern inTermediate Redshift ESO Supernova Search (STRESS) concludes that, at least in one respect (rate), Ia SNe are just as they always were.

CC (core collapse) SNe rates do seem to have a cosmic time dependence however.

Stay tuned for the next thousand, hundred thousand, or million SNe observations ....

OTOH, this 28 page preprint may provide grist for the Jerry mill:

As with any natural phenomenon, the more carefully we study the more we learn about it. This is what seems to be happening with supernovae, as the papers to which links have been provided in this thread show. Perhaps there was some unfounded optimism regarding the utility of supernovae as probes of cosmic expansion. However, the Ellis preprint mentioned is better described as cautious rather than negative in tone. While it may be true that supernovae are not the ideal standard candles that cosmologists once thought they could be, it remains to be conclusively demonstrated that the use of supernovae data to do cosmology is a hopelessly flawed enterprise. Also, Jerry should be as careful as the authors of this paper are not to turn his negative estimates and expectations into self-fulfillling prophecies.

One should not be so quick to forget that supernovae data is not the only evidence for an accelerating universe. Supernovae data with greater errors bars, at this point, seem only to limit are ability to distinguish between competing dark energy models rather than overturn the basic notion (supported by many different data sets) that we live in a spatially flat accelerating Universe.