👉 The term "ultrastellar" refers to stars that are so massive and dense that they can emit light at wavelengths longer than visible light. These stars, also known as supermassive black holes, are responsible for a significant portion of the overall luminosity in the universe. They are also thought to be the most extreme sources of radiation, with temperatures reaching up to several billion degrees Kelvin. The concept of "ultrastellar" has been proposed by many astrophysicists and
