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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."
"twice as bright as others of its type"
/. reader then. ;)
Obviously not a
biopowered.co.uk - catalytically cracking triglycerides for home automotive use since 2008. Just say no to big oil!
Models are just that, models. Change them when the universe shoves reality down your throat. Far too many people think that math defines the universe instead of describing it.
init 11 - for when you need that edge.
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!
The observation suggests supernovae of this type are not "standard candles" as previously thought, which could affect their use as probes of dark energy - the mysterious force causing the expansion of the universe to accelerate.
If true, this wouldn't just affect their use as probes of dark energy. These standard candles are used to tell how far away things are and how fast they are moving. The age of the universe could be in doubt.
But I have a hunch this particular supernova will turn out to be an anomaly. Not that I'm a astrophysicist or anything.
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
It's a pretty familier story, and essential for the advancement of science.
The standard candle was a theory, one that worked well, and now it's in doubt, indicating either that its wrong, or it's incomplete. I'd vote for the latter personally.
That's usually a safe bet...
That's how things move forward.
I shortcut this process. I proved one of my hypothesis wrong even though it had withstood initial tests which indicated correctness. It probably saved a lot of time, but lost me a conference trip, dammit.
Dark energy? the mysterious force? Oh, I get it, we found the death star!
That was funny right? *nudge**nudge*
I'm not trying to make people mad; I'm trying to make people think!
1) Never trust anything you read in New Scientist.
2) Consider the following, discovered on Google:
My emphasis added.
Probably not. Gravitational lensing would cause a noticible shift in the star's spectrum.
So what you are saying is....eh....the thing with the........when the thing with the other thing goes...to.....because the wotsit is like the..eh....so, do they run Linux in their lab?
allllright Tom Cruise, time to get off your soapbox!
Type Ia supernovae are indeed one of the last rungs on the distance ladder; they can be used to estimate distances to very distant galaxies.
No, that's an overstatement. Type Ia supernovae are one of several different indicators used to estimate distances to very distant galaxies -- not the only one. _If_ we suddenly thought that the luminosity of _all_ Type Ia supernovae was significantly higher, _then_ we would have to re-examine the agreement between distances derived from Type Ia supernovae and other methods. The net effect might be a slight shift in the value of the Hubble constant, which is used to estimate distances to really, really distant objects.
However, if only 1 in 100 or fewer Type Ia supernovae are more luminous than expected, it won't make any significant difference in studies which use lots of supernovae.
Michael Richmond "This is the heart that broke my finger."
mwrsps@rit.edu http://stupendous.rit.edu