Why did Population III stars lack planets?
Population III stars were the very first stars in the universe, back in a time when it consisted exclusively of hydrogen and helium. Any heavier elements would only form once massive stars died in violent supernova explosions, and therefore only be available to the following generations of stars. Yet planets, which form simultaneously with their star, rely on these heavy elements. In the predominant paradigm of planet formation, a solid core has to form from these components before any gaseous atmospheres can build up. So the basic building blocks to form planets were not available around these earliest stars.
Even if some planets did form around these unusual stars, they would be far from habitable: with surface temperatures of about 100,000 Kelvin, their host stars emitted deadly ultraviolet radiation. At the end of their short lives, Population III stars exploded in devastating supernovae. While this was certainly not a very inviting neighbourhood to live in, these very explosions produced the heavy elements that today’s planetary systems, including our own, are made of. Dr Jeremy Schnittman is a research astrophysicist at NASA’s Goddard Space Flight Center, Maryland