Not all stars become black holes
In 2011, a scientific paper raised the exciting but problematic possibility that black hole formation happens more simply than anticipated. Until this date, the scientific community was of the opinion that only very massive, late-life stars could become black holes. These circumstances would make possible a sufficiently large amount of matter, confined in a space small enough for its formation. Hirotada Okawa, Vitor Cardoso and Paolo Pani, from the Centro Multidisclinar de Astrofísica (CENTRA) at Instituto Superior Técnico, revisited and updated the contours of this problem. The results of their study will be published in the journal Physical Review D and highlight the prevailing view: black holes are extremely rare in our universe.
The paper published by two Polish scientists in 2011 suggested that in anti-de Sitter space-time black holes form, regardless of initial conditions. Anti-de Sitter space-time is the simplest solution of Einstein's equations of general relativity. Polish researchers have shown that anti-de Sitter space-time can act as an open box with a mirrored interior. The reflection of matter inside the box could thus create a point where the density is infinite and form a black hole.
Using their Baltasar Seven Suns supercomputer, the CENTRA researchers ran a set of simulations to solve Einstein's equations and determine if these 'boxes' exist in the real Universe. The research group concluded that in the Universe the 'boxes' would allow energy dissipation and that in the case of less massive objects, such as our Sun, the dissipated energy would be sufficient to block the formation of a point with infinite density. Paolo Pani, FCT Researcher selected in the 2013 Call , summarizes the results "We found that in realistic cases matter collapse can occur, but it is not that easy."
Vitor Cardoso also adds that the future of a star is not necessarily to turn into a black hole - "Gravity doesn't always win!"