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A cosmic lens made of a galaxy cluster helped spot a supernova from the Universe’s childhood.
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A massive galaxy cluster acts as a giant lens. Its gravity warps the fabric of space, and the light of distant objects, bending around this curvature, is amplified and split into multiple images. It was this natural magnifying glass that helped the James Webb Space Telescope spot the faint flash of a supernova in an incredibly small galaxy at the edge of the visible universe.
Supernova SN Eos exploded when the Universe was only a billion years old. Its light traveled for 13 billion years to reach us, and along the way, the cluster’s spacetime deflected it, creating multiple images. The spectrum of the flash, the dispersed light, revealed that the progenitor star contained almost no elements heavier than helium. Astronomers call such elements “metals” (not iron or copper, but anything heavier than helium). This is the first direct evidence that massive stars were born in a metal-poor young Universe.
SN Eos is the most distant supernova with a recorded spectrum. It erupted right after the “dark ages,” when the Universe was just becoming transparent to ultraviolet light.
Each such find is an additional lens through which we see the early epoch more clearly. It allows us to calculate how often the first stars ignited and how quickly galaxies grew.
