We just discovered a new type of astronomical object. A galaxy in which gas outshines the stars it contains
.A billion years after the Big Bang, or 12.7 billion years ago, the universe was different than it is now. There were less heavy elements in nebulas from which new stars form. These atomic nuclei come to be in subsequent generations of stars that die as supernovas or, more calmly, spreading them around. At such a young age, the universe wasn’t old enough for many generations of stars to live and die. However, such gas nebulas that were heavy nuclei-poor allowed more massive and luminous stars to form than it is possible now. They lived short lives, exploded as supernovas, and illuminated nearby space and gas in young galaxies.
It turns out that one galaxy called 9422, 12.7 billion years ago, was unique because it had so many massive stars at once that they bombarded nebulas so much with their light that the gas in them shone more intensely than the stars themselves. These gigantic suns had temperatures of about 80,000 C/140,000 F. In comparison, the most massive stars in the contemporary universe have only temperatures around 45,000 C/80,000 F.
Gas shining more intensely than stars in young galaxies was already predicted in our models of the young universe, and this lucky discovery confirms our models. At 1 billion years old, galaxy 9422 doesn’t contain the very first stars called Population III anymore, which would be made almost entirely by hydrogen and helium that the universe was born with. The hot stars it contains are already some of the earliest, but subsequent generations formed from some ashes of earlier stars.
The fascinating discovery would not have been possible without the James Webb Telescope, which gives us an unprecedented view of the very old universe just after the Big Bang.