When a massive star dies, it usually violently explodes and then the gravity at its core creates a collapse that eventually forms a black hole. However, after running simulations, scientists now believe that the very first stars died differently: they exploded but burned out so quickly that no black hole was left behind.
This revelation comes from astrophysicists at the University of California Santa Cruz and the University of Minnesota. They ran numerous simulations on a supercomputer at the Department of Energy's National Energy Research Scientific Computing Center (NERSC) and Minnesota Supercomputing Institute, using code, called CASTRO, developed by the Lawrence Berkeley National Laboratory.
Through the simulations, the team discovered that stars about 55,000 to 56,000 times the size of our sun became unstable after about 1.69 million years and then collapsed. This collapse triggered the unification of the heavy elements, which released a vast amount of energy, even more than that which binds the star together. This caused the collapse to stop and resulted in a supernova.
The heavy elements get mixed up throughout the remainder of the star, causing it to burn up, without leaving behind a black hole.
The code, CASTRO, looked at specific attributes that are unique to older stars, as well as what happens when stars die, such as relativistic effects, nuclear burning and stellar convection.
"We found that there is a narrow window where supermassive stars could explode completely instead of becoming a supermassive black hole -- no one has ever found this mechanism before," says Ke-Jung Chen, lead author of the study.
These ancient stars were the first in the Universe and produced heavy chemical elements that flew out into space and became the building blocks for newer stars. Some of these stars exploded and sent elements, such as carbon and silicon, to its own galaxy, as well as to other nearby galaxies. Sometimes, the explosion created more stars in its galaxy.
The research team believe that this sort of supernova would create a unique signature that telescopes could pick up in the near-infrared wavelength. Future missions will look for that tell-tale sign of the explosions of ancient stars, including those involving the European Space Agency's Euclid and NASA's Wide-Field Infrared Survey Telescope.
Of course, one scientist is challenging the existence of black holes. If her theories prove true, that will change what we know not just about ancient stars, but about newer ones, too.
