Theoretical physics suggests that there is no upper bound on the mass of a black hole. According to general relativity, black holes can form from the gravitational collapse of massive objects, such as stars. As matter collapses under its own gravity, it can reach a point of infinite density known as a singularity, surrounded by an event horizon from which nothing can escape, including light.
The mass of a black hole is determined by the amount of matter that collapses to form it. As long as there is sufficient matter available, the black hole can continue to grow in mass. In theory, there is no known limit to how massive a black hole can become.
However, there are physical constraints and considerations that come into play. One such constraint is the availability of matter in the universe. As the universe evolves, matter becomes more dispersed, making it less likely for extremely massive black holes to form.
Additionally, there are astrophysical processes that can influence the growth and evolution of black holes. For example, black holes can accrete matter from their surroundings, gaining mass over time. They can also merge with other black holes, resulting in larger black holes. These processes can set practical limits on the growth of black holes based on the availability of matter and the dynamics of their environments.
Observations of black holes in the universe provide evidence for the existence of supermassive black holes with masses millions or even billions of times that of our Sun. While there is no strict theoretical upper bound, the largest black holes observed so far are in the range of billions of solar masses.
It's important to note that our understanding of black holes is based on the current theories of general relativity and quantum mechanics. The interplay between these two theories is an active area of research, and future advancements may lead to further insights into the behavior and limits of black holes.