There is a strange, metal-poor galaxy lurking in the distant universe. The very first image released by the James Webb Space Telescope (JWST) team revealed a galaxy with far fewer heavy elements than we would expect, which might mean that it鈥檚 sucking up pristine hydrogen gas from intergalactic space.
at the University of Cambridge and his colleagues examined the light from three galaxies shown in JWST鈥檚 first deep-field image to measure the abundance of elements that astronomers call metals, meaning anything heavier than hydrogen. These heavy elements are formed in the centres of stars, which distribute them throughout space when they die.
鈥淭hese galaxies apparently formed in very short timescales after the big bang, so we don鈥檛 expect them to have evolved considerably into very massive and very developed systems with lots of dust and aged stars,鈥� says at the University of California, Los Angeles who was not involved in the work.
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Two of the galaxies that Curti鈥檚 team examined were about 29.4 billion light years away from Earth, while the third was about 30.2 billion light years away. The nearer galaxies had less metals than galaxies in our part of the universe, which was as expected, but the further one had almost no metals at all 鈥� just 2 per cent of the metal content of the sun. 鈥淭his is one of the most extremely metal-poor objects that we have ever seen,鈥� says Curti.
Spotting such a strange galaxy so soon into JWST鈥檚 observing campaign was a surprise. 鈥淲e sort of expected that galaxies at these high [distances] would be peculiar, but probably no one was expecting to immediately see evidence for this extremely metal-poor galaxy in the very first data,鈥� says Curti.
In the local universe, a galaxy鈥檚 metal abundance is closely linked to its mass and star formation rate, but this galaxy seems to buck that trend. That probably means that it recently underwent some sort of dramatic change, says Curti, possibly swallowing up hydrogen gas from the space between galaxies. As we get more detailed observations of other extremely distant galaxies, researchers will be able to figure out whether such metal-poor galaxies are common in the distant universe or if this one was an anomaly.
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