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Supernova 1994D. The supernova is the bright point in the lower-left. It is a type Ia thermonuclear supernova like those described by Howell. The supernova is on the edge of galaxy NGC 4526, depicted in the center of the image.   Credit: NASA/Hubble Space Telescope

Dark Energy… And Zombie Stars!

4 Jul , 2011

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It’s called a Type Ia supernovae and it shines with the luminosity of a billion suns. For all intents and purposes, once they explode they’re dead… But it ain’t so. They might have a core of ash, but they come back to life by sucking matter from a companion star. Zombies? You bet. Zombie stars… And they can be used to measure dark energy.

Why are Type Ia supernovae findings important? Right now they’re instrumental in helping researchers like Andy Howell, adjunct professor of physics at UCSB and staff scientist at Las Cumbres Observatory Global Telescope Network (LCOGT), take a closer look at the mysteries of dark energy. “We only discovered this about 20 years ago by using Type Ia supernovae, thermonuclear supernovae, as standard or ‘calibrated’ candles,” said Howell. “These stars are tools for measuring dark energy. They’re all about the same brightness, so we can use them to figure out distances in the universe.”

As a rule, white dwarf stars which end their lives as Type Ia supernovae have approximately the same mass. These findings were so regular that they are considered a base rule of physics, but rules are usually made to be broken. In this case there’s a new class of Type Ia supernovae – one that goes beyond the typical mass. These stars that go beyond their limits have scientists confused as to their nature. We know they are part of a binary system… But shouldn’t only the white dwarf be the one to explode?

D. Andrew Howell Credit: Katrina Marcinowski

Howell presented a hypothesis to understand this new class of objects. “One idea is that two white dwarfs could have merged together; the binary system could be two white dwarf stars,” he said. “Then, over time, they spiral into each other and merge. When they merge, they blow up. This may be one way to explain what is going on.” Now astrophysicists utilize Type Ia supernovae to track universal expansion. “What we’ve found is that the universe hasn’t been expanding at the same rate,” said Howell. “And it hasn’t been slowing down as everyone thought it would be, due to gravity. Instead, it has been speeding up. There’s a force that counteracts gravity and we don’t know what it is. We call it dark energy.”

Once upon a time, Albert Einstein introduced the cosmological constant to help justify his theory of relativity, but it only applied to a static state. It didn’t take long before Edwin Hubble corrected him and Einstein later referred to his failure to predict the expansion of the universe as the “biggest blunder” of his life. But it wasn’t. “It turns out that this cosmological constant was actually one of his greatest successes,” said Howell. “This is because it’s what we need now to explain the data.”

We could argue all day about dark energy and its properties, along with whether or not it constitutes three-quarters of our known universe. However, it is Howell’s theory that it just might be a property of space. “Space itself has some energy associated with it,” said Howell. “That’s what the results seem to indicate, that dark energy is distributed everywhere in space. It looks like it’s a property of the vacuum, but we’re not completely sure. We’re trying to figure out how sure are we of that – and if we can improve Type Ia supernovae as standard candles we can make our measurements better.”

Unlike historic supernova observations, today’s technology allows even the backyard astronomer to make discoveries and report them. Take the latest M51 findings for example… It’s not just the eyes of the expert on the skies. Thanks to advances in cameras and equipment, we’re looking further away – and more accurately – than ever before. “Now we have huge digital cameras on our telescopes, and really big telescopes,” said Howell, “We’ve been able to survey large parts of the sky, regularly. We find supernovae daily.”

“The next decade holds real promise of making serious progress in the understanding of nearly every aspect of supernovae Ia, from their explosion physics, to their progenitors, to their use as standard candles,” writes Howell in Nature Communications. “And with this knowledge may come the key to unlocking the darkest secrets of dark energy.”

As we dig through the ditches and burn through the witches… wink

Original Story Source: UC Santa Barbara.


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Ivan3man_At_Large
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Ivan3man_At_Large
July 4, 2011 10:16 PM

As we dig through the ditches and burn through the witches…

Click Here.

Wezley Jackson
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Wezley Jackson
July 4, 2011 11:42 PM

quoting from a comment in your link:
24 people are not wise in the way of science, weigh the same as a duck, didn’t get better from? being turned into a newt, whose fathers smelled of elderberries, do not know the average airspeed velocity of an unladen swallow, fell over the rail half-way across the bridge of? death, got retarded from hearing “Ni, Payng and Nuuuuuwong” and has no way of knowing how to always look on the bright side of life!

Wezley Jackson
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Wezley Jackson
July 4, 2011 11:52 PM
As an armchair cosmologist I really appreciated Mr Howell’s insights – “Space itself has some energy associated with it,” said Howell. “That’s what the results seem to indicate, that dark energy is distributed everywhere in space. It looks like it’s a property of the vacuum, but we’re not completely sure. We’re trying to figure out how sure are we of that – ” I am starting to understand why many scientists favor Dark Energy as a placeholder or hypotheses… I also find refreshing Mr Howell’s candor and honesty in simple easy to understand language. Nice article Ms Plotner – I also enjoyed Mr Steve Nerlich’s insights in some recent articles here about DE that if indeed there is… Read more »
Lawrence B. Crowell
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Lawrence B. Crowell
July 5, 2011 3:26 AM

Dark energy is distributed quite evenly in space, and in time. This still obeys the laws of thermodynamics.

LC

Ken Lord
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July 5, 2011 4:48 AM

If I’m not mistaken, the part that may violate thermodynamics is how all the new space that is being created as the universe expands all has this energy, seemingly created out of nothing.

But I know that I’m an ignorant layman so i won’t speculate on it coming from other universes or branes crashing together.

Lawrence B. Crowell
Member
Lawrence B. Crowell
July 5, 2011 11:48 AM
The FLRW equation for the scale parameter a = a(t)in flat space is (a’/a)^2 = 8?G?/3 where a’/a = H, the Hubble parameter and a’ = da/dt. There is an equation of state for the mass-energy in the spacetime d(?a^3)/dt + pda^3/dt = 0 which is most relevant for the case of radiation and matter dominated universe with p = ?/2 and ? a^3 = constant for radiation. The general equation of state is p = w?. The equation of state p = -? corresponds to a case where the total energy is zero and the first law of thermodynamics is dF = dE – pdV = 0 means the energy that is increased in a unit volume… Read more »
HeadAroundU
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HeadAroundU
July 6, 2011 1:52 AM

No need for such a long post. Not very effective. You just need one sentence to say that energy creation is zero. Maybe one equation. You have to work with what they said. It’s a creation of spacetime and constant density of Dark energy that seems to come out of nothing. Am I right?

Anonymous
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Anonymous
July 6, 2011 9:06 AM

You are entitled to your opinion but I for one greatly appreciate Lawrence’s posts. Though I struggle with the maths, I also learn a lot from them and they add a great deal of science to the popularised basic stories.

Lord Haw-Haw.
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Lord Haw-Haw.
July 9, 2011 5:46 PM

Dr. Crowell writes in a thought provoking manner, it is an honor to have him here on the UT forums.
Invariably when you cross-reference his postulations his articulations are meticulously fastidious.
A mathematical posit is hereby proposed whereby a graph with an algebraic formulae be incorporated acceding proportional benevolence thus eliciting future fan “likes” in his favor.

Olaf
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Olaf
July 6, 2011 5:08 PM

I love the maths part of LC, even if I do not understand everything when he repeats enough I will. And his explanation is very clear compared to what you have to read from text books.

Chris Ellison
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July 5, 2011 12:46 AM

A well placed Rob Zombie lyric at the end there from the song Dragula. grin

Anonymous
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Anonymous
July 5, 2011 7:52 AM
Sorry Tammy but this article seems a tad confused: “It’s called a Type Ia supernovae and it shines with the luminosity of a billion suns. For all intents and purposes, once they explode they’re dead… But it ain’t so. They might have a core of ash, but they come back to life by sucking matter from a companion star.” I thought that a Type Ia fully disrupted the progenitor white dwarf so there would be nothing left onto which to accrete? Perhaps you are suggesting this might not always be the case and what is left could go through another cyle of accretion and explosion. “Howell presented a hypothesis to understand this new class of objects. “One idea… Read more »
Lawrence B. Crowell
Member
Lawrence B. Crowell
July 5, 2011 12:05 PM

I found myself pondering this as well. I had thought that SNIa’s blew themselves into space with nothing left. The explosion of a white dwarf that passes the Chandrashekhar is a sort of giant 1.3 solar mass hydrogen bomb core. It was my understanding that nothing remained such as a core, but the whole thing blew itself into space. This all seems to be putting additional conditions on these SNIa’s, which could mean there is now a range of different physical objects we now think of as SNIs’s.

LC

Anonymous
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Anonymous
July 5, 2011 7:29 PM

It’s the article. Compare it with this version:

http://www.sciencedaily.com/releases/2011/06/110630131836.htm

“[Howell] calls Type Ia supernovae “zombie” stars because they’re dead, with a core of ash, but they come back to life by sucking matter from a companion star. Over the past 50 years, astrophysicists have discovered that Type Ia supernovae are part of binary systems — two stars orbiting each other. The one that explodes is a white dwarf star. “That’s what our sun will be at the end of its life,” he said. “It will have the mass of the sun crammed into the size of the Earth.””

It makes it clearer that he was using the term to refer to the progenitor white dwarf, not a leftover after the supernova.

Lawrence B. Crowell
Member
Lawrence B. Crowell
July 5, 2011 7:52 PM

This is then the standard model for SNIa’s. LC

Ivan3man_At_Large
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Ivan3man_At_Large
July 5, 2011 4:20 PM

Don’t blame Tammy; she was just reporting on what Howell said in the original press release.

Steve Nerlich
Member
July 5, 2011 7:48 AM

Dark energy is a phenomena hypothesised in response to the observational data that the universe is expanding with a uniform acceleration.

OK. But couldn’t we just say that the universe is expanding with a uniform acceleration and leave it there?

I can’t see what we gain by saying that there must be some utterly mysterious form of energy that appears out of nowhere, breaks the laws of thermodynamics, expands the universe and then disappears without trace after having done so. What is the point of flagging this place-marker concept as ‘energy’?

Anonymous
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Anonymous
July 5, 2011 1:19 PM

Without there being some additional effect, the expansion should slow, and that is what happened for the first 6 billion years or so, but since then the rate has been increasing. The acceleration was initially negative but is now positive so can’t be described as “uniform”.

Torbjorn Larsson OM
Member
Torbjorn Larsson OM
July 5, 2011 2:07 PM
Albert Einstein introduced the cosmological constant to help justify his theory of relativity, but it only applied to a static state. It didn’t take long before Edwin Hubble corrected him and Einstein later referred to his failure to predict the expansion of the universe as the “biggest blunder” of his life. But it wasn’t. Neatly related as befits a short article. Now I’m an impatient student of history, and general relativity isn’t a subject I’ve studied, but FWIW I think the expansion of the compressed history goes something like this: Earlier observation and theory, including Hubble’s own observations, had all suggested a static universe. (If threatening paradoxes like why the sky is dark, instead of hot and bright… Read more »
Anonymous
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Anonymous
July 6, 2011 9:17 AM
http://en.wikipedia.org/wiki/Friedmann%E2%80%93Lema%C3%AEtre%E2%80%93Robertson%E2%80%93Walker_metric#Name_and_history “The main results of the FLRW model were first derived by the Soviet mathematician Alexander Friedmann in 1922 and 1924. Although his work was published in the prestigious physics journal Zeitschrift für Physik, it remained relatively unnoticed by his contemporaries. Friedmann was in direct communication with Albert Einstein, who, on behalf of Zeitschrift für Physik, acted as the scientific referee of Friedmann’s work. Eventually Einstein acknowledged the correctness of Friedmann’s calculations, but failed to appreciate the physical significance of Friedmann’s predictions.” Friedmann had presented Einstein with the solution before Hubble’s observations, but he was so intent on modelling the static universe he missed the implications. Had he realised the consequence, he could have predicted the expansion before… Read more »
Anonymous
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Anonymous
July 6, 2011 9:17 AM
http://en.wikipedia.org/wiki/Friedmann%E2%80%93Lema%C3%AEtre%E2%80%93Robertson%E2%80%93Walker_metric#Name_and_history “The main results of the FLRW model were first derived by the Soviet mathematician Alexander Friedmann in 1922 and 1924. Although his work was published in the prestigious physics journal Zeitschrift für Physik, it remained relatively unnoticed by his contemporaries. Friedmann was in direct communication with Albert Einstein, who, on behalf of Zeitschrift für Physik, acted as the scientific referee of Friedmann’s work. Eventually Einstein acknowledged the correctness of Friedmann’s calculations, but failed to appreciate the physical significance of Friedmann’s predictions.” Friedmann had presented Einstein with the solution before Hubble’s observations, but he was so intent on modelling the static universe he missed the implications. Had he realised the consequence, he could have predicted the expansion before… Read more »
Steve Nerlich
Member
July 6, 2011 5:58 AM

Thanks – but again, I have no issue with the observational evidence that the universe is expanding in an accelerating manner – which the late time SW effect aptly demonstrates.

I agree it is extraordinary that space-time is appearing out of nowhere and I have no explanation for this – I just don’t see how we can ascribe the cause of it to invisible energy.

I fail to see how the SW effect can be interpreted as a direct observation of dark energy, but maybe it’s just me.

Lawrence B. Crowell
Member
Lawrence B. Crowell
July 6, 2011 4:04 PM
Einstein introduced the cosmological constant as a way of reversing the collapse of matter in the entire universe. If you have a lot of galaxies arrayed through space with no relative motion to speak of their mutual gravity will result in their collapse. Einstein then used a bit that Kahler had mathematically explored, which is a Ricci tensor that is proportional to the metric itself. So Einstein introduced the ?g_{ab} into his field equations to reverse this collapse. Hubble found not long afterwards that the universe was expanding and so Einstein threw out his term. Friedmann wrote a solution to the Einstein field equations which is similar to the dynamics of a projectile. If the energy of the… Read more »
Torbjorn Larsson OM
Member
Torbjorn Larsson OM
July 6, 2011 5:34 PM

Thanks, that makes sense. I reread my comment, and found that while I wasn’t explicit the text may be read as implying that Einstein thought the blunder was the cc itself. That was probably what I was thinking when writing it.

So again thanks, for providing the history details!

Torbjorn Larsson OM
Member
Torbjorn Larsson OM
July 6, 2011 6:39 PM
I agree it is extraordinary that space-time is appearing out of nowhere and I have no explanation for this – I just don’t see how we can ascribe the cause of it to invisible energy. I fail to see how the SW effect can be interpreted as a direct observation of dark energy, but maybe it’s just me. First, let me note that no one says that expansion of space-time is caused by an apparently visible* “invisible” energy. Expansion is ongoing, it is the acceleration that is of concern here. Those are entirely different things. (Say, when warming water, heat is responsible for increased temperature, increased heat flow for accelerated temperature increase.) Essentially, without dark energy expansion would… Read more »
Torbjorn Larsson OM
Member
Torbjorn Larsson OM
July 5, 2011 2:28 PM
I think you have to read lcrowell’s comment just above. Dark energy isn’t only consistent with thermodynamics, it seems to be needed to preserve it. (Preserve local zero energy density but also global zero energy of FLRW universes.) Didn’t we all have this conversation a few weeks back? How there is no mystic energy appearing from ‘nowhere’. Or conversely how can anyone accept that spacetime expands out of ‘nowhere’ but balk that some of its constituents does!? To add to that – now we are leaving physics to go into the world of argumentation “do and don’t” – and take on another characterization that strikes me as unfair here: inflation admits multiverse solutions where universes appears, expands briefly… Read more »
Lawrence B. Crowell
Member
Lawrence B. Crowell
July 5, 2011 3:20 PM
Dark energy with the equation of state w = -1 imposes a conservation of the de-Sitter vacuum free energy. The cosmological constant written according to a source in a stress-energy tensor is ?g_{??}= 8?G/c^4(?g_{00} – pU_iU_j) where the energy density ? is a time-time component of the tensor and the pressure p is a space-space component. The condition p = -? gives conservation of total energy, or the free energy dF = d? – pdV is zero. In effect the negative pressure performs “negative work,” and work = energy, so this absorbs the dark energy which appears to keep pouring forth from the expansion of the universe. Indeed this subject keeps coming up, and a couple of months… Read more »
Anonymous
Guest
Anonymous
July 6, 2011 9:11 AM

Are we going to have to start talking about “Dark Pressure” too now wink

Lawrence B. Crowell
Member
Lawrence B. Crowell
July 6, 2011 1:12 PM
A dark pressure, sure enough. Of course one has to see there is a big problem with all of this. Dark energy is a quantum vacuum effect, but where the quantum eigen-states are unknown. Various theoretical proposals have been made, but so far things do not work very well. The problem is this is often approached with some large number of quantum modes, or a huge ensemble of degrees of freedom, which is problematic. I tend to think the vacuum states of the de Sitter spacetime is due to a fermion condensate, with type II string realizations, where the condensate state is similar to superconductivity. In that case all the degrees of freedom of the superconducting carriers (Cooper… Read more »
Rich Moraghan
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July 6, 2011 3:48 AM

It would seem the container has mass…how surprising.

spirulina
Guest
July 6, 2011 5:40 PM
I read an extract about dark energy: ‘Dark energy’ is not energy, it has energy which is a subtle but important difference. Energy is a property of dark energy, expressed in joules, calories, BTU’s etc.. Similarly, matter is not mass. Again, mass is a measurable value, a property of matter. Specifically, one property that Dark Energy does not have in its ‘at rest’ or inertial, non accelerating state is ‘mass’. However, in any type of acceleration mode it does have mass and, as a consequence, will exhibit matter like attributes. If this seems difficult to envisage, the photon, or any electromagnetic wave, is another example of something which if it were ever ‘at rest’ would appear to have… Read more »
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