IIT Guwahati researchers find new clues to how stars die

Researchers from the Indian Institute of Technology (IIT) Guwahati have revealed important clues to understand the death of massive stars and have also revealed the problems with the existing models.

The study, done in collaboration with researchers from Max Planck Institute for Physics, Munich, Germany, and Northwestern University, US, indicates that all three species of the neutrinos from the supernovae are important contrary to the common treatments with only two flavors.

Neutrinos are considered to be the most crucial ingredient in the mechanism of core collapse supernova explosions, death of large, massive stars. And supernovae is the super explosions at the time of death of large massive stars are considered to be the cradle of birth for new stars and synthesis of the heavy elements in nature.

At the end of their life, the stars, especially massive ones, collapse resulting in an immense shock wave that causes the star to explode, briefly outshining any other star in its host galaxy.

The study of supernovae and the particles they release helps us understand the universe because almost all matter that makes up the universe is a result of these massive explosions.

"However, the mechanism of these super explosions is not yet completely solved and has remained one of the enigmas of naturea," said the researcher, Sovan Chakraborty, Assistant Professor, Department of Physics, IIT Guwahati.

The solutions to the toughest challenges to the core collapse mechanism of the huge supernovae come from the tiniest subatomic particles called neutrinos, according to a paper published in the journal Physical Review Letters (PRL).

During the core collapse supernova explosion, neutrinos are created in several particle processes. Due to their neutral nature and extremely weak interaction with stellar matter the neutrinos escape the dying star and carry 99 per cent energy of the collapsing star.

Thus the tiny neutrinos are the only messenger bringing information from the deepest interiors of the star.

"This information is very crucial for the reason that in the extremely dense supernovae core neutrinos interact with other neutrinos and may interchange flavors. This conversion may happen rapidly (in nanosecond time scale) and flavor interchange can affect the supernovae process as the different flavors are emitted with different angular distribution," Chakraborty said.

"These 'fast' conversions are nonlinear in nature and are not confronted in any other neutrino sources but supernovae. We for the first time did a non-linear simulation of fast conversion with 'all' the three neutrino flavors in supernovae," Chakraborty added.

This becomes possible as new supernova simulations show the presence of muons in the supernovae and in turn produce asymmetry between muon neutrinos and antineutrinos, taken to be zero otherwise, implying three flavor effects.

<em>(IANS)</em>.