Massimo Pascal wasn’t planning to study the galaxy cluster SMAC 0723. But as soon as he saw the cluster glittering in the first image from the James Webb Space Telescope, or JWS, he and his colleagues couldn’t help themselves.
“We were like, we have to do something,” says Pascal, an astronomer at the University of California, Berkeley. “We can’t stop ourselves from analyzing this data. It was so exciting.”
Pascal team is one of several groups of scientists who saw the first JWS images and immediately rolled up their sleeves. In the first few days after images and the data used to create them were made public, scientists have estimated the amount of mass the cluster contains, uncovered a violent incident in the cluster’s recent past and estimated the ages of the stars in galaxies far beyond the cluster itself.
“We’ve been preparing for this for a long time. Myself, I’ve been preparing for years, and I’m not very old,” says Pascal, who is in his fourth year of graduate school. JWS “is really going to define a new generation of astronomers and a new generation of science as a whole.”
2022Far-flung galaxies
Mapping out mass in the cluster is also essential to decoding the properties of the more distant galaxies in the background of the image, Mahler says. “You need to understand the cluster and its magnification power to understand what’s behind.”
Some scientists are already investigating those distant galaxies in detail. The first JWS data include not just pretty pictures .but also spectra, measurements of how much light an object emits at various wavelengths. Spectra allow scientists to determine how much a distant object’s light has been stretched — or redshifted — by the expansion of the universe, which is a proxy for its distance. Such data can also help reveal a galaxy’s composition and the ages of its stars.
“The main thing that limits the study of star formation in galaxies is the quality of the data,” says astrophysicist Adam Carnal of the University of Edinburgh. But with the vastly improved data from JWS, he says, he and his team were able to measure the ages of stars in those remote galaxies.
Carnal and colleagues turned their attention to the spectra of the distant galaxies just a few days after the SMAC image was released. They measured the redshifts of 10 galaxies, five of which were particularly distant, the team reports in a paper submitted to arXiv.org on July 18. One had already as the most distant galaxy ever seen, with light that was emitted just 500 million years after the Big Bang 13.8 billion years ago. The other four shone as late as 1.1 billion years after the Big Bang.
All 10 galaxies were relatively young when they emitted the light captured by JWS, Carnal says. They had all switched on their star formation just a few million years earlier. That’s not especially surprising, but it is interesting.
“The ability to look at these small, faint galaxies … gives you a sense of how all galaxies must look when they start forming stars,” Carnal says.
Scientists hope to use JWS to find the first instances of star formation ever. Other early results suggest they’re already getting close.
Some galaxies in a JWS image of another cluster may hearken from an even earlier time, as early as 300 million years after the Big Bang, two research teams report in a pair of papers submitted to arXiv.org on July 19. One of those galaxies seems to have already built up a spiral disk about a billion times the mass of the sun, which is surprisingly mature for such an early galaxy.
And a tally of galaxies seen in the SMAC 0723 image suggests that galaxies with mature disks, rather than disorganized blobs or ones made up mostly of dark matter, may have been more common in the very early universe than previously thought, another team reports in an arXiv.org paper submitted July 19. That means those early disks might not be outliers.
“Definitely these galaxies are a big deal, but it remains to be seen how exciting they will look in the context of a few months’ progress with JWST,” Carnal says. The best is yet to come.
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