The two characteristics of a star that make it most likely to become a black hole are:
- Its mass is greater than 20 times the mass of the sun.
- It is dying.
Stars with significantly high mass (typically over 20 solar masses) have the potential to end their life cycle in a supernova explosion, which can lead to the formation of a black hole. Additionally, a dying star typically undergoes processes that can lead to the collapse of its core, contributing to the potential formation of a black hole.