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Supernova Casts Doubt on "Standard Candle"
Krishna Dagli writes, "A supernova more than twice as bright as others of its type has been observed, suggesting it arose from a star that managed to grow more massive than theoretically thought possible. The observation suggests that Type 1a supernovae may not be 'standard candles' — all having the same intrinsic luminosity — as previously thought. This could affect their use as probes of dark energy, the mysterious force causing the expansion of the universe to accelerate."
I think you are exactly right. I am a mathematician. People should understand that all of mathematics is an abstract concept created by humans. Why does 2+3 = 5? Because we said it does...not because it is universally true. Sometimes (in the case of 'models'), we put some math together to attempt to explain what we see. As we discover new behaviors in whatever system we're looking at, we have to change the math. So, this article is about one of those instances.
That's how we Americans do geography. We know where Hawaii is, and we know that Canada is (vaguely) north of us, and France is somewhere in Asia.
No folly is more costly than the folly of intolerant idealism. - Winston Churchill
So why do I think this is a 'good thing'? As the article speculates, it is likely that this supernova was different because of some rotational process or perhaps colliding stars, or some other exotic combination. This is exactly the sort of process that can be used as a test of supernova models to see how well they do. Over all I find this a very exciting observation and hopefully it produces more new science!
I study supernovae for a living.
i g_tab/nature05103_F1.html
The Nature paper in which this work is published has a figure showing all the measurements of this supernova's brightness; you can see it on Nature's web site at
http://www.nature.com/nature/journal/v443/n7109/f
There are four measurements near time of maximum light, in the red (r) and near-infrared (i) passbands. There are many more measurements starting about 15 days after maximum light in the rest frame, including some in a blue-green (g) passband. Here's what the researchers did to find the maximum brightness of this supernova, so that they could compare it to others:
a) fit models based on the light curves of other supernovae to the r and i measurements,
and the late-time g measurements
b) choose a different passband -- the greenish V passband of the Johnson-Cousins system,
which is closest to their own g passband (the one with no data at max light)
c) use their models to estimate what the light curve in the V filter would have been
This can be a tricky business. Their major conclusion, that this supernova was more luminous than typical ones, is probably correct, but their claim that they can measure the peak magnitude in the V-band to an uncertainty of 6 percent seems a bit bold.
As the press release states, if atypical SNe are very rare, then this probably doesn't have any major impact on the use of Type Ia SNe in cosmology.
Michael Richmond "This is the heart that broke my finger."
mwrsps@rit.edu http://stupendous.rit.edu
I think his point would be more accurately expressed as this:
"Why is 2 + 3 = 5?"
Because the arbitrary definitions which we assigned to the symbols 2, 3, 5, +, and = happen to represent real-world concepts that exhibit the behavior that 2 + 3 = 5, and not because there is any abstract universal rule that "2 + 3 = 5" and we simply need to find real-world behavior to prove it. That is, the real-world behavior has always existed, but the mathematical language used to express it was invented by us and assigned to those behaviors specifically to make the mathematics true.
(Or something, it's early.)
--K
I don't get it.