A black hole with a mass of one trillion suns would be an extremely massive object. To put it into perspective, the mass of the sun is approximately 2 x 10^30 kilograms. Therefore, a black hole with a mass of one trillion suns would have a mass of approximately 2 x 10^42 kilograms.
The size of a black hole is determined by its mass and the density of matter within it. In simple terms, a black hole's size is defined by its event horizon, which is the boundary beyond which nothing, not even light, can escape its gravitational pull. The event horizon of a black hole is directly proportional to its mass.
For a black hole with a mass of one trillion suns, its event horizon would be significantly larger than that of stellar-mass black holes, which are formed from the collapse of massive stars. However, accurately calculating the size of such a massive black hole would require complex equations of general relativity.
To our current understanding, it is theoretically possible for black holes of such immense mass to exist. Supermassive black holes with millions or billions of solar masses have been observed at the centers of galaxies, so the concept of black holes with a trillion solar masses is not inconceivable. However, it is worth noting that we have not yet observed a black hole of that exact mass, and our understanding of black holes at such extreme scales is still an active area of research.
It's important to remember that while we can make theoretical predictions and calculations based on our current knowledge, further scientific advancements and observations are necessary to fully understand the nature of black holes, especially those at such enormous scales.