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Astronomers have used the James Webb Space Telescope (JWST) to reveal extraordinary details about a galaxy in the early universe, seen as it was just 360 million years after the big bang.
Since JWST launched, it has been finding galaxies that are so distant the light now reaching us from them was emitted during the early life of the cosmos. These galaxies have been more numerous and appear brighter than expected, suggesting there is something missing in our knowledge of how galaxies grow at young ages.
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One of those galaxies, GLASS-z12 (originally called GLASS-z13), is so bright that it has been estimated to be nearly 1 per cent the mass of the Milky Way. Galaxies were expected to take much longer to reach this size, perhaps up to a billion years.
at the National Astronomical Observatory of Japan and his colleagues have now used JWST to study GLASS-z12 in greater detail than ever before, and published their findings in two papers.
Though a technique called spectroscopy, they picked apart the light of the galaxy to reveal a signature of hydrogen, the intensity of which suggests the presence of gargantuan young stars up to 400 times the mass of the sun and barely 10 million years old.
But there was also a 鈥渟urprising鈥� signature of oxygen, says Zavala, suggesting that some stars in the galaxy had already exploded as supernovae and released heavy elements. This could mean the galaxy had already experienced bursts of star formation in its short 100-million-year existence.
鈥淪o it鈥檚 not very long, constant star formation,鈥� says Zavala. 鈥淩ather, you have several short episodes of strong star formation. This is what we call 鈥榖ursty鈥� star formation.鈥�
Those bursts are likely to have been driven by the young galaxy eating gas from surrounding intergalactic space. As this gas is consumed, it may ignite bursts of star formation, forming stars at rates of up to 10 times the mass of our sun per year.
Those newly formed stars could then suppress star formation to just one solar mass per year because their radiation pushes the gas away, says team member at the Astronomical Observatory of Rome in Italy. He refers to GLASS-z12 as a 鈥淩osetta stone鈥� for understanding galaxy formation.
The already significant bulk of GLASS-z12, a billion times that of our sun, suggests it may eventually grow into a titan of a galaxy, many times the mass of the Milky Way. 鈥淭his galaxy will be the progenitor of the most massive galaxies,鈥� says Zavala.
Yet despite its mass, the galaxy is strangely compact, perhaps just 130 light years across 鈥� tiny compared with the 100,000-light-year width of the Milky Way. 鈥淚t鈥檚 really a bomb,鈥� says Castellano. 鈥淚t鈥檚 extremely dense and compact.鈥�
at the Space Telescope Science Institute in the US, which runs JWST, says the work is a key technological milestone for the telescope. Earlier JWST work had performed spectroscopy for later galaxies in the cosmos, but the new observations essentially 鈥渟kipped over the entire history of the universe and went for one of the most distant objects that has been discovered鈥�, she says. 鈥淚t was quite amazing.鈥�
Other galaxies will be studied at this age of the universe, but GLASS-z12 gives us an early look at what to expect. 鈥淚t鈥檚 probably the most massive object in this epoch,鈥� says Zavala. 鈥淚t鈥檚 not breaking anything, but this is definitely a unique system.鈥�
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