As the James Webb Space Telescope (JWST) has begun sending back its first science data, scads of researchers around the world have reported new galaxies, each more distant than the last.
The distance to a cosmic object is denoted by what’s known as redshift. This works a bit like the Doppler effect, in which a sound seems to change in pitch depending on whether it is moving towards or away from the listener. The faster a galaxy is moving away from the Milky Way, the higher its redshift – and because of the expansion of the universe, the more distant a galaxy is, the faster it moves away from us and the redder it looks.
We knew JWST would spot incredibly distant objects, with correspondingly high redshifts, but the immediate cascade of such distant galaxies it has revealed was surprising to many astronomers. “I don’t think any of us really expected to see quite this many sources at such high redshifts,” says at the University of California, Los Angeles. “We all expected to be surprised in some way or another, but not so quickly or so drastically.”
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Before JWST, the most distant object spotted had a redshift of about 11, meaning it formed within about 400 million years of the big bang. JWST data has now been used to identify several galaxies with apparent redshifts of 13 and , meaning they formed within 300 million years of the big bang.
So far, we don’t know much about these galaxies, and most of their redshifts have not yet been confirmed. “Right now we’re just grabbing all the fruit – we still have to figure out which are the good ones and which are the rotten ones, but right now it’s just gimme gimme gimme,” says at NASA’s Goddard Space Flight Center in Maryland. “We’re still in the initial harvest stage, and we don’t really know what’s important yet.”
“It’s really quite an amazing mess right now, but it’s been this sudden lurch forward and then we’ll take some time and take a breath,” says at the Harvard-Smithsonian Center for Astrophysics. After a whirlwind of new findings, the tough task of double-checking everything will begin, generally by taking more detailed measurements of the objects’ light in a process called spectroscopy.
That will be particularly important for the most distant candidates. For example, a team led by at the University of Missouri claims to have found a galaxy at , so it would have to have formed within 180 million years of the big bang – far earlier than we expect galaxy formation to have begun. “Our results are completely unexpected and are at odds with all previously favoured predictions,” says Yan, who declined to comment on the details of his team’s work before it is peer-reviewed.
“That, essentially, would break galaxy evolution,” says Roberts-Borsani. If there really is a galaxy at a redshift of 20, it could mean that we have deeply misunderstood the physics of galaxy and star formation in the early universe.
“The capabilities of Webb are such that it could observe a redshift 20 thing if it were there, but there’s a lot of scepticism whether it could be there,” says at the University of Manchester in the UK. “Something that extreme needs a closer look and validation from multiple people.”
It might take a while to get that closer look. JWST’s schedule is booked far in advance, and so is the other telescope big enough to do the necessary spectroscopy, the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile. So unless researchers can convince the directors of those telescopes to let them skip the queue, these observations will have to wait.
Even before the necessary checks, it is clear that there are at least some galaxies that are brighter and more distant than expected. “If even 20 per cent of the galaxies reported in the last week turn out to be at the redshifts that they are reported to be at, it’s strong evidence that these things form very early and very quickly, and get very massive and very bright very early,” says Naidu.
Once we know which of are real and formed in the extremely early universe, we can start studying them in more detail. “In the big picture we’re asking, how did it all get started?” says Rigby. “How quickly do galaxies stop being boring places of just hydrogen, helium and dark matter and start actually making the rest of the periodic table that we’re made of?”
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