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."

Comments

Canada-France-Hawaii telescope?

[Anonymous Coward]

(note: I'm Canadian)
Why is the telescope called "Canada-France-Hawaii" instead of "Canada-France-USA" telescope?
Or did Hawaii separate from the US recently? ;-)

Thomas Dz.

Re:The universe will out

[rocketman768]

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.

This is a GOOD thing....

[trip11]

...as supernova are not well understood. First off I am not an astrophysicist, though I am a high energy physicist (and have taken some astro classes). One thing that has been discussed in nuclear classes I have taken is how little we understand just how a supernova functions at the atomic level. The number of competing effects going on during the collapse of a star is just amazing. You have gravitational pull, thermal pressure, rotational 'pressure', electromagnetic forces in a regular star. Now you start to collapse the star and you have to add in the transition of millions of individual nuclei becoming in effect one large nucleous as they all mearge. (not to mention the energy output from this). In effect the strong force comes into play along with the standard EM and gravitational forces. It gets much more complicated than that, but it has been several years since those classes.

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!

more important than 'probes of dark energy'

[i_should_be_working]

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.

Re:more important than 'probes of dark energy'

[The_Wilschon]

I doubt it. Our actual measurements of dark energy won't come under much increased doubt. Although Type IA supernovae the first (IIRC) indicator of dark energy, we still have a number of other indicators. I was just as PASCOS 2006, and saw several talks on dark energy, where various quantities related to the acceleration of the universe were really overconstrained by about 4-5 different measurements. The only one I can recall at the moment is gravitational lensing. The neat thing is that although overconstraint has the possibility to show an inconsistency, it doesn't do so here. The measurements all line up at one point (well, a distribution around one point, but that distribution is quite nicely peaked in one location, indicating consistency.).

Similarly, Type IA SN are not the only mechanism by which we measure the age of the universe, so I'm not too concerned. The other reason I'm not too concerned is that the age of the universe was already in doubt. Another talk at PASCOS dealt with something else that I can't recall at the moment (curse my memory in the morning!) that cast into simultaneous doubt all or nearly all of our universe age indicators. IIRC, according to his talk, the universe could well be 20% older than our current best estimate.

Of course, since all these are not quite my field (I was at PASCOS for the particle physics), I can't answer for whether or not these guys were just crazies and all the cosmologists were ignoring them, or if these are serious problems that will be dealt with in the next few years. I'd be inclined, however, to assume that they were quite legit.

Re:The universe will out

[The_Wilschon]

So why is it that electric fields follow the law of superposition, which is an additive law working precisely as we said addition should thousands of years before we ever imagined electric fields? Furthermore, how is it that we can "prediscover" phenomena? We develop a model to describe existing data, and whoops!, there's another phenomenon implicit in our model, and sure enough when we look for it in reality, there it is!

This is a fairly poor summarization of the argument made by Tom Siegfried (used to be chief science writer for the Dallas Morning News, now he's somewhere else) in his book Strange Matters.

Perhaps you are right, and mathematics is just something we came up with. However, where did we come up with it from? Our brains. Our brains are part of the universe, so if the universe is goverrned by laws which can be well expressed in mathematical language, one might predict that brains would invent mathematics.

Skeptical...

[Anonymous Coward]

Two points:

1) Never trust anything you read in New Scientist.

2) Consider the following, discovered on Google:

In section 5.4, for the SNe that were thrown out, are you sure that all of them had enough data to accurately measure the peak? I was just looking at SNLS-03D3bb, and there are only 3 or 4 points in in g-band (restframe B), and they are all >~ 20 days after maximum light. So the B-band measurement here is a total extrapolation. Also, in the fits Julien gave me I think it was 0.4 mag off, not 0.7. Anyway I think 03D3bb should be thrown out because there is not enough data, not because it is peculiar (although we can mention that). long mails about that. No clear outcome. To summarize. The 2 SNe Ia outliers and spectro. peculiar are very badly fitted (i.e. the sampling of the lightcurves is sufficient to blow up the chi2). Cutting on the chi2 of the fit is worrying. the 2 Ia* may be IC's. We'll rephrase this section

My emphasis added.

Re:The universe will out

[KutuluWare]

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

Re:The universe will out

[Jeff DeMaagd]

There have already been doubts about the uniformity of brightness of a supernova. Some people think that non-polar and non-equatorial viewpoints are possibly less brigtht than polar or equatorial views.

Re:The universe will out

[TheRaven64]

And given the base definitions, 2+3=5 is universally true.

2+3=5 is not univserally true, it is true within the framework of a common set of axioms. Here is an example of a simple set of axioms which allow us to prove that 2+3 = 5 (within the framework of those axioms):

Let s(X) be the successor function applied to the variable X.
Let 0 be a symbol in our algebra.
Let 0 = 0. (1)
Let s(X) = s(X) if and only if X = Y. (2)
We now have equality defined.

Let X + 0 = X. (3)
Let X + s(Y) = s(X) + Y. (4)
Let X + Y = Y + X. (5)
We now have addition defined.

We define a set of symbols such that 2 = s(s(0)), 3 = s(s(s(0))), and 5 = s(s(s(s(s(0))))).
2+3 = 5 is therefore equivalent to s(s(0) + s(s(s(0))) = s(s(s(s(s(0))))).

We can rewrite this by applying our axoims (axiom number given in brackets) so that:
s(s(s(0))) + s(s(0)) = s(s(s(s(s(0))))) (4)
s(s(s(s(0)))) + s(0) = s(s(s(s(s(0))))) (4)
s(s(s(s(s(0))))) + 0 = s(s(s(s(s(0))))) (4)
s(s(s(s(s(0))))) = s(s(s(s(s(0))))) (3)
s(s(s(s(0)))) = s(s(s(s(0)))) (2)
s(s(s(0))) = s(s(s(0))) (2)
s(s(0)) = s(s(0)) (2)
s(0) = s(0) (2)
0 = 0 (2)

This gives axiom 0, and so is true.

Anyone wanting to play with these ideas in a more hands-on way should download a prolog implementation (I recommend SWI Prolog). You can implement these axioms in prolog as the following program (the first two are implicitly defined):

% add(X,Y,Z) predicate represents X + Y = Z
add(X,0,X).
add(X,s(Y),Z) :- add(s(X),Y,Z).
add(X,Y,Z) :- add(Y,X,Z).

You can then ask it questions in the following way:

?- add(s(s(0)),s(s(s(0))),Five).

Five = s(s(s(s(s(0)))))

Yes

Your homework from this post is to extend this system to define multiplication.

Re:The universe will out

[Anonymous Coward]

Do you often refute your own arguments?

If mathematics were just some invention of ours, then the universe would need a calculator in hand to figure out what to do next. We know the universe follows relatively simple mathematical laws. So, what?--Does it then comply to our whims and inventions? No, of course not! Our mathematics complies to its nature; not just in our use of it, but in the very nature of mathematics.

It's absurd how well mathematics models the world. So absurd, it may be impossible to explain it otherwise.

Re:The universe will out

[inviolet]

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.

Quoted for truth. I want to elaborate (i.e. ramble) on it a bit . . .

Numbers are indeed a deductive system: they are true because they are defined to be true. They are true in all conceivable universes. This makes them useful but also hollow: they contain no empirical content, and hence are immune to all conceivable experimental results.

Nevertheless, they (and all other deductive symbols) can participate in inductive statements, such as "2 algae cells will combine with 3 fungi cells to produce 1 lichen".

Re:Gravity Lensing?

[Anonymous Coward]

Probably not. Gravitational lensing would cause a noticible shift in the star's spectrum.

And why would that be? Wouldn't the light be blueshifted as it fell into the gravitational potential of the lens, and then redshifted as it escaped, for a net spectral shift of zero?

Re:The universe will out

[Control Group]

This is certainly true, but don't undersell math, either. The amazing part of math is that, given certain axioms and definitions crafted to describe and fit easily-observed physical phenomena, logical extrapolations of those axioms and definitions can accurately describe physical phenomena we have not yet observed.

That is, mathematics is not purely descriptive as it relates to science. As an example, it is my understanding that the phenomenon of time dilation as velocity increases towards c was first "observed" as a result of mathematical manipulations of exsiting models, long before it was (or could be) experimentally observed.

If math were purely descriptive, this would not be the case - or, if it were, it would be only by sheerest chance; the exception, rather than the rule.

I agree, of course, that math comes out of description; 2+3=5 because those numbers represent specific physical quantities, and when you have real items in those quantities, they behave in that fashion. However, I can't help believing that there is something inherently "real" about math itself, since the logical structure of math agrees so well with physical reality so often - enough so, in fact, that the mathematical understanding of a physical phenomenon can predate observation of that physical phenomenon.