Slashdot Mirror
Astronomers Explode Virtual Supernova
DynaSoar writes "Scientists at the University of Chicago's Center for Astrophysical Thermonuclear Flashes have created a simulation of a white dwarf exploding into a type 1a supernova. Using 700 processors and 58,000 hours, they produced a three second movie showing the initial burst that is thought to be the source of much of the iron in the universe. Understanding these supernovas is also important to testing current cosmological theories regarding dark matter and dark energy, as their brightness is used as a measurement of distance, and discrepancies found in the brightness of very distant supernovas consistently seem to indicate a change in the speed of expansion of the universe over time."
http://flash.uchicago.edu/website/research/gallery /home.py
for all alternative OS users out there.
Does anyone else see the "face" that is created during this explosion? I see closed eyes, a nose and even a mouth(all tongue in cheek) ROFLMAO... sorry poor joke..... would love to see this at full speed.
I never RTFA, but maybe it was a "cumulative" 58,000 hours across 7,000 processors? That seems a lot more feasible to me... but maybe they did start it over 6 years ago :p
It's probably 58,000 processor hours, which on 700 processors is closer to 83 hours in real time.
"It is possible to commit no errors and still lose. That is not a weakness. That is life." -Peak Performance
SG-1 did visual graphics, not a full-fledged simulation.
supernovas
Shouldn't that be supernovae?
Have you read my journal today?
If the 58000 hours is not cumulative, then this represents 4.6 millenia of computing time. If that were done with one processor, about 180 supernovae would explode in our galaxy during the computation.
"Though the computer simulation took a total of 58,000 hours and more than 700 computer processors, the actual process from start to finish--when the star explodes--played out in just three seconds." (Third paragraph under the subhead "Crash Code", ninth paragraph overall).
:)
Yep, definitely nowhere in the story. Not anywhere. Definitely not in plaintext, sitting there, waiting to be read
Gah that article is awful. They link to pretty pictures and blurbs mostly and never really explain what these things are, why they are important or give you any real sense of scale. So since I like to beat on the drum of better communication of science, here is a little more detail to add to the good einhverfr's post.
The progenitors of SNIa are most likely white dwarfs composed of carbon nitrogen and oxygen, probably with a companion star from which they are stripping matter. They are very compact on the order of a few thousand kilometers at most, and really dense - more than the mass of the sun. They aren't hot enough to support fusion - they are supported by Pauli pressure; quantum mechanics doesn't allow two electrons in the same state at the same time so though gravity tries to compact these objects there is a Pauli pressure outward to balance it.
This can't go on forever in these progenitor systems however, and if the white dwarf strips enough matter of its companion to get to ~1.4 solar masses (the Chandrashekar limit) then Pauli pressure isn't strong enough to balance gravity and the star begins to collapse and when that happens pressure and temperature rises and somewhere a nuclear fusion flame ignites. Details about what happens near collapse, and where and how the flame ignites, and how many there are and how they progress are still debated. In this particular model they are considering only a single flame (so far) and its a "gravitationally confined detonation" (GCD - the name of this particular model).
Its a little difficult to get a sense of scale from those videos, though there are numbers in the bottom corner. The flame starts of near or just of center and becomes bubble/mushroom shaped through a Rayleigh-Taylor instability and breaks the stellar surface in under a second. Its less than another second before the ash and flame from the bubble collides at the opposite end of the star. This flame crashing into itself (see video 1) causes compression and a detonation.
Theres been a lot of debate as to whether its a deflagration or a detonation or whether it transitions from one to the other and how and when that happens and us poor graduate students just hope they don't go crazy over details of the progenitors during our qualifying examinations. This is notable because there appears to be a growing number of voices who are saying that a detonation is necessary. These events are so standard because they all become SNIa if they get near 1.4 solar masses. There is a fair bit of diversity (and some just crazy objects) and most of that probably arises from details during the explosion which is why modeling them is partly why the models are so important.
There is still a lot of modeling left to do. This flame is producing a lot of heavy elements (there is O, S, Ca, Mg and Si in the early spectra - the silicon feature is around 6150 angstrom in the rest frame and is the marker of a Ia at low to moderate redshifts). As the outer layers expand and become more transparent you see more of the material produced during the explosion and a lot of this is Nickel (Ni-56) which decays to cobalt and powers the light curve so you get this typically 2 week rise and then a slow fall off. Later times most of the Ni has become cobalt which is decaying to iron and you see these elements in the spectrum. The energies we are talking about here are about 10^45 Joules. A H bomb by contrast is 10^15 Joules so 30 order of magnitude. Unless you can picture 10^30 H bombs going off its hard to get a feeling for this number but thats generally the case with numbers in cosmology.
There are a lot of empirical relations you see from the lightcurve, which are exploited to standardize them (for instance the brighter the supernova, the slower its rate of decline, and there are relations for the colour...) and if a model can replicate them and match the observed lightcurves and spectra then this is a very impressive accomplishment. I skim
Reality must take precedence over public relations, for nature cannot be fooled.
In fact, the word is built out of two Latin adjectives, literally it means an "abovenew". Invented words follow this rule, hence the plural of octopus is octopuses, of satellite is satellites, and of millennium is millenniums. The plural of "vertebra" is "vertebrae" because it is an actual Latin word, not an invented modern one.
Incidentally, while pursuing this very pedantic note, "satellites" is correct plural but the singular of the original word is "satelles". And the original word is pronounced sat-ell-it-ees. We are a long way from Latin.
Pining for the fjords
Both could be correct if you use them properly in the sentence. Supernovae when it's the subject, supernovas when it's the object. Assuming we're treating "supernova" as a regular 1st-declension latin feminine noun.
Strictly speaking, super (as a preposition of space or location, in this case) takes nova in the ablative case, so the ending on nova is a long a (ahhhhh). If we were writing in Latin I don't know that we'd use the -ae ending for the plural at all. In fact, I'm not sure what the plural would be. I assume we'd throw a pronoun before "super nova", maybe "eae super nova" (they who are above the new [thing]), and continue on with the sentence with "eae" (feminine they) as our subject. Or we could use Illae (those) as our subject, which might be less proper and more vulgar-latin slangy.
occultae nullus est respectus musicae - originally a Greek proverb