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Reconstructing The Death Of Supernovae In 3D Offers New Insights

March 18, 2014
Image Caption: Three-dimensional turbulent mixing in a stratified burning oxygen shell which is four pressure scale heights deep. The yellow ashes of sulphur are being dredged up from the underlying orange core. The multi-scale structure of the turbulence is prominent. Entrained material is not particularly well mixed, but has features which trace the large scale advective flows in the convection zone. Also visible are smaller scale features, which are generated as the larger features become unstable, breaking apart to become part of the turbulent cascade. The white lines indicate the boundary of the computational domain. Credit: Arnett, Meakin and Viallet/AIP Advances

Lee Rannals for redOrbit.com – Your Universe Online

An astrophysicist has created a new three-dimensional model that provides new insight into the death throes of supernovae.

The model, created by W. David Arnett, Regents Professor of Astrophysics at the University of Arizona, is the first to represent the start of a supernova collapse in 3D. It shows how the turbulent mixing of elements inside the dying stars causes them to expand, contract and spit out matter before exploding.

Existing models of supernova envision the star in a series of concentric circles with heavier elements like iron and silicon in the center and lighter elements like carbon, helium and oxygen at the surface. According to these models, the heavier elements exert a powerful gravitational pull on the lighter elements, compacting the star and increasing pressures to drive up temperatures to create neutrinos.

These other models claim that as neutrinos go shooting out of the star, they take out energy with them, which reduces the ability of the lighter gases to fight the core’s gravitational pull. Instead of cooling down, the star contracts further eventually turning into a “runaway” situation, Arnett said.

Researchers must simplify these models in order to run them on supercomputers because they are very large and complex. In order to do this, they must limit their models to flow to one or perhaps two dimensions.

Arnett’s new model shows a star with a turbulent interior that spits out star remnants prior to the final explosion, similar to how heating a pot causes water to boil over the edge.

“We still have the concentric circles, with the heaviest elements in the middle and the lightest elements on top, but it is if someone put a paddle in there and mixed it around. As we approach the explosion, we get flows that mix the materials together, causing the star to flop around and spit out material until we get an explosion,” said Arnett, who described the model in the journal AIP Advances.

The astrophysicist’s 3D model is based on better data and faster computers than previous models.

“It would have taken 40 years to run these models on the supercomputers I used in the 1970s. They were feeble compared with my smartphone,” Arnett says.

He said that scientists need more data because supernovae are extremely rare and difficult to find. Telescopes like the Katzman Automatic Imaging Telescope (KAIT) and Palomar Supernova Factory will help to pile on data because they use sophisticated electronics to help spot supernovae.

After finding supernovae, researchers use larger telescopes to help gather even more information about the exploding stars. These treasure troves of data have produced a new understanding of how some stars die.

“Instead of going gently into that dark night, it is fighting. It is sputtering and spitting off material. This can take a year or two. There are small precursor events, several peaks, and then the big explosion,” Arnett said. “Perhaps we need is [sic] a more sophisticated notion of what an explosion is to explain what we are seeing.”


Source: Lee Rannals for redOrbit.com - Your Universe Online



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