Cosmic Titans: How Big Can Stars Grow?

The size of the universe’s most massive stars is a question that changes depending on the era of cosmic history you examine. In the early universe, the first stars were behemoths hundreds of times the mass of our Sun, born from primordial hydrogen and helium. Today, the largest known star, UY Scuti, is a red supergiant with a radius about 1,700 times that of the Sun, though its mass is only about 30 times greater. The challenge in measuring stellar mass lies in the fact that the most massive stars are also the most unstable, often ending their lives in supernova explosions. Recent observations from the European Southern Observatory suggest that the upper limit for stellar mass may be around 150 solar masses under current cosmic conditions. This limit is dictated by the Eddington luminosity, where radiation pressure balances gravitational collapse. As technology advances, astronomers continue to push the boundaries of our understanding, using tools like the James Webb Space Telescope to peer into the distant past and observe the formation of these cosmic giants. The study of massive stars is not just about size; it’s about understanding the life cycles of the universe itself.