Astronomers armed with early data obtained by the James Webb Space Telescope (JWST) are hunting galaxies that existed just a few hundred million years after the Big Bang. Rohan Naidu, an astrophysicist based at the Center for Astrophysics | Harvard & Smithsonian (CfA), and his colleagues have been particularly good at uncovering these cosmic relics.
Just a few days after the James Webb Space Telescope’s first images were beamed across the planet, Naidu and his collaborators dropped a paper that reverberated across the web, picking up a real head of steam on social media. Using data from the ‘scope, the researchers announced that they’d discovered a candidate for the most distant galaxy ever seen, dubbed GLASS-z13. Then, not even a week later, many different groups had found candidate galaxies ever farther away.
It’s not surprising we have yet another candidate.
In a pre-print paper, released on Aug. 5 and yet to undergo peer review, Naidu and colleagues have detailed another distant galaxy candidate, from one of JWST’s early release science programs, known as CEERS-1749. It’s an extremely bright galaxy that, if confirmed, would have existed just 220 million years after the Big Bang — and it could also rewrite our understanding of the cosmos.
But there’s a huge catch.
CEERS-1749 could be one of the most distant galaxies we’ve ever seen or it could be lurking much closer to home. Essentially, the data seems to indicate two possible places for the galaxy to be — and we won’t know which one is correct without observing it a lot more. That’s earned it the title of “Schrodinger’s galaxy candidate” in the paper submitted to pre-print repository, arXiv, on Aug. 4.
So, how can a galaxy like Schrodinger (the name we’re running with because it’s way more fun than CEERS-1749) seem to be in two different places? It’s all about redshift.
To determine how far away a galaxy lies, astronomers study wavelengths of light. Specifically, they’re interested in a phenomenon of light known as “redshift.” In a nutshell, light waves leaving distant galaxies get stretched over time, shifting the waves down the electromagnetic spectrum and making them more, well… red. So, ultraviolet light leaving a galaxy like Schrodinger won’t reach Earth as ultraviolet light. Instead, it will be redshifted down into the infrared, which is great for us because that’s just the kind of light JWST searches for.
And JWST has various filters, looking at distinct wavelengths of infrared. In examining a galaxy like Schrodinger, you can flick through the wavelengths like you might flick through a photo album. On the first few pages — less red wavelengths — you won’t see a thing. Then, as you turn through and the wavelengths become more red, the ghost of a galaxy appears. In the most redshifted wavelengths, at the back of the album, the galaxy is a clearly defined object.
Redshift is denoted by the parameter z and higher z values mean a more distant object. One of the confirmed most distant galaxies discovered to date, GN-z11, has a z value of 11.09. In the case of Schrodinger, the research team state it could have a z value of around 17. That would mean this light is from a time some 13.6 billion years ago.
It would also mean we might need to rethink our models of how galaxies evolved in the earliest days of the universe — galaxies from that long ago should not be this bright, at least according to the model we currently use to explain our cosmos.
But maybe we don’t need to break physics just yet.
The team suggest there is good environmental evidence that Schrodinger’s z value might be around 5, which would mean its light is about 12.5 billion years old. Other galaxies in the region around Schrodinger all lie at about this distance. It might even be that Schrodinger is a satellite galaxy of one of its more massive neighbours.
But wait! There’s more: Another group of researchers also studied this exact same galaxy from the early release data, publishing their own results to arXiv on the same day. Jorge Zavala, an astrophysicist at ALMA Japan, and his team added to the JWST data with data from an Earth-based telescopes in the French Alps and Hawaii.
They came to the conclusion that Schrodinger might be an imposter masquerading as a high-redshift galaxy when it’s actually a much closer, dusty galaxy undergoing rapid star formation.
The take home message? Work on this perplexing galaxy candidate is incomplete. JWST has been able to study the intensity of the light emitted by Schrodinger but we need more measurements. In particular, spectroscopy will allow astrophysicists to scrutinize its redshift more accurately. The only barrier now is time — getting enough time on telescopes around the world to study Schrodinger and solve the puzzle.