Simulations Reveal Ancient Stars Die Differently

Oct 03, 2014 06:34 AM EDT

This image is a slice of the interior of a supermassive star of 55,500 solar masses along the axis of symmetry.

(Photo : Ken Chen, University of California at Santa Cruz) It shows the inner helium core in which nuclear burning is converting helium to oxygen, powering various fluid instabilities (swirling lines). This "snapshot" from a CASTRO simulation shows one moment a day after the onset of the explosion, when the radius of the outer circle would be slightly larger than that of the orbit of the Earth around the sun.

Using simulations, scientists have mapped out the unusual death of ancient and primordial stars that give birth to more stars, and more elements.

Astrophysicists from the University of California, Santa Cruz (USCS) and the University of Minnesota ran the simulations. They worked at the Department of Energy's (DOE's) National Energy Research Scientific Computing Center (NERSC).

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As scientists observe the deaths of stars, they noticed these deaths leave black holes in the wake of a star's destruction.

They noted, however, there were 55,000 to 56,000 stars larger than our sun that left no black holes upon their deaths. Instead, they exploded into supernovae.

Ke-Jung Chen, a postdoctoral researcher at USCS and lead author of the study, said there's a narrow window where supermassive stars explode into supernovae, not leaving any traces of black holes.

"No one has ever found this mechanism before," he added.

Without the ancient stars present to actually study, they turned to simulations to model the life of such stars. To accurately create the simulation, they used several important codes.

KEPLER is a one-dimensional stellar evolution code that takes into account key processes like nuclear burning, stellar convection, general relativistic effects, among others.

They found primordial stars could live for 1.69 million years before succumbing to instability due to general relativistic effects, thus leading to a collapse.

Upon collapse, these stars rapidly synthesize heavy elements like oxygen, neon, magnesium, silicon, and helium at its core. Through this process, the collapse is halted and the star instead explodes into a massive supernova.

Using the CASTRO code to analyze the death of the star, they reversed the explosion and saw the elements made at a star's core were being infused into the whole body of the star.

It's through this infusion of elements through the entire star that supernovas enrich the galaxy with elements and build new stars.

TagsAncient stars, primordial, Supernova, Ke-Jung Chen, KEPLER, CASTRO