Using 3-D models, physicists have created a mathematical code that cracks a mystery about stellar development and reconciles a discrepancy with the Big Bang theory of the universe's evolution.

The discrepancy with the Big Bang theory revolves around the amount of helium-3 gas present in the universe. 

The theory predicts a certain amount of the gas in the universe, but low-mass stars — about one to two times the size of our sun — also make helium-3 as a side product of burning the hydrogen in their cores, according to Professor John Lattanzio from Monash's School of Mathematical Sciences and director of the Centre for Stellar and Planetary Astrophysics. 

"It's been thought that when the star becomes a giant it mixes the helium-3 to its surface and, near the end of its life, spews the helium-3 into space just before it becomes a planetary nebula.

"But there are inconsistencies with the amount of helium-3 predicted to be in the universe and the amount that's actually there; there's much less than expected," said Lattanzio.

Some scientists theorized that stars destroy this helium-3 by assuming that nearly all stars were rapidly rotating, but this still conflicted with the Big Bang theory.

Lattanzio, in collaboration with Dr. Peter Eggleton and Dr. David Dearborn from the Lawrence Livermore National Laboratories in the U.S., ran 3-D computer models that identified the mechanism of how and where low-mass stars destroy the helium-3 they produce during evolution.

"Prior to our work, it was perceived that the helium-3 in the envelope was largely indestructible, and would be blown off later into space, thus enriching the interstellar medium and causing the conflict with the Big Bang," said Eggleton.

"What we find is that helium-3 is unexpectedly destructible, by a mixing process driven by a phenomenon that has been ignored so far."

There is a "core flash" near the end of a star's life, and it was around this time that the computer models showed a small instability in the movement of the gases in the star, said the researchers.

"When we looked at this in 3-D we found this hydrodynamic instability caused mixing and destroyed the helium-3 so that none was released into space," said Lattanzio.

"This confirms how elements evolved in the universe and makes it consistent with the Big Bang," said Dearborn.

The research appeared in Thursday's edition of the journal Science.