First Prototype Model Finds Missing Link In Massive Star Explosions

Posted: Nov 30 2015, 11:22pm CST | by , Updated: Dec 1 2015, 6:24pm CST, in News | Latest Science News


First Prototype Model Finds Missing Link in Massive Star Explosions
A supercomputer visualization of the toroidal magnetic field in a collapsed, massive star, Credit: Robert R. Sisneros (NCSA) and Philipp Mösta.

The supercomputer model explains how enormous magnetic fields fire off bursts of gamma rays.

When massive stars collapse, they create explosions called Hypernovae. Some of these hypernovaes are really explosive and are observable across the universe.

Now astrophysicists have created a computer model that stimulates how hypernovae generates the enormous magnetic fields needed to explode a dying star and how gamma rays burst as a result of it.

The stimulation demonstrates that when a rotating star collapses, the magnetic field attached to it spins faster and faster and transforms into a magnetic field that is a million billion times more massive than the magnetic field of Earth. 

These magnetic fields generated by stellar dynamos are so powerful that they can produce oppositely directed blasts of highly energetic gamma rays. 

"A dynamo is a way of taking the small-scale magnetic structures inside a massive star and converting them into larger and larger magnetic structures needed to produce hypernovae and long gamma-ray bursts," said Philipp Mösta, a UC Berkeley postdoctoral fellow and lead author of the study.

"That kicks off the process. People had believed this process could work out. Now we actually show it."

Researchers used Blue Waters, one of the most powerful supercomputers in the world and it created a stimulation that reflects finer details than ever before. The graphic stimulates mere 10 milliseconds in the collapse of a massive star but is capable enough to explain strange cosmic phenomena.

Scientists already know that gamma rays fire off when massive dying stars collapsed but the missing link was how a star with a normal magnetic field can rev such a monstrous magnetic field required to trigger massive explosions. 

"We expect only a small fraction of stars to be spinning rapidly enough before collapse to explain pulsar spin periods of milliseconds," said co-author Christian Ott, a professor of theoretical astrophysics at the California Institute of Technology. "But if a star is spinning this fast, then there is a lot of energy in the rotation. The problem has been how to extract that and dump it into the explosion.”

Gamma-ray bursts are very brief and bright and were not observed until 1967 nuclear bomb tests. But the first prototype model of a collapsing star provided a close look at how it actually works out. The massive stellar explosions are rare and are called Type Ic broadline supernovae.

“What we have done are the first global extremely high resolution stimulations of this that actually show that you create this large global field from a purely turbulent one, said one of the authors Phillip Mosta. “This stimulation also demonstrate a mechanism to form magnetors, neutron stars with an extremely strong magnetic field, which may be driving a particular class of 

very bright supernovae.” 

Scientists are trying to improve these models so they can answer more perturbing questions.

Source: UC Berkely 


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Hira Bashir covers daily affairs around the world.




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