Collapsar

A collapsar, also known as a failed supernova, is a type of supermassive star that undergoes gravitational collapse at the end of its life, directly forming a black hole without a traditional supernova explosion. This phenomenon occurs when the core of a very massive star (typically exceeding 40 solar masses) collapses under its own gravity. The immense gravitational force overwhelms all outward pressure, leading to the formation of a black hole.

Unlike standard core-collapse supernovae, where the collapsing core bounces back against the surrounding material, creating a powerful explosion, in a collapsar, the core's collapse is so complete and rapid that there is no bounce. The entire star essentially implodes into the black hole.

Collapsars are theorized to be associated with long-duration gamma-ray bursts (GRBs). The rapidly rotating black hole formed during the collapse can generate powerful jets of plasma that are ejected along the star's rotational axis. These jets, interacting with the surrounding stellar material, can produce the intense bursts of gamma rays observed from Earth.

The exact mechanisms and conditions required for a collapsar to form are still under investigation. Factors such as the star's initial mass, rotation rate, and metallicity (abundance of elements heavier than hydrogen and helium) are thought to play crucial roles in determining whether a star will undergo a traditional supernova or collapse directly into a black hole.

Collapsars represent an important stage in stellar evolution and are crucial for understanding the formation of black holes and the origin of some of the most energetic events in the universe, such as long-duration GRBs.