The new observatory may have found the most ancient starlight we’ve ever seen—and it’s only the beginning.
The newly discovered galaxy looks a little bit like a
squashed tomato, or maybe the crown of a cherry-flavored Ring Pop. Just a red
blob, so blurry and edgeless that the first time I looked, I had to make sure
I’d put my contact lenses in. I say these things because without invoking
little earthly associations, I’m not sure how we’d even begin to fathom what
this cosmic object is: not just a galaxy, but perhaps the most distant galaxy
we have ever seen.
The galaxy was spotted by the James Webb Space Telescope,
the newest and most powerful observatory in the world, which kicked off
operations last week. The starlight that Webb spotted from this galaxy left its
glittery boundaries long ago, before, well, nearly everything. According to two
separate teams of astronomers, that blurry tomato we’re seeing is the way this
galaxy looked just 300 million years after the universe came into existence.
So, so much has happened since then—our sun flickered on, the planets were
formed, life arose on Earth, Ring Pops were invented. Webb has rewound that
tape. The glow of the most distant galaxies, the kind that the observatory was
designed to detect, takes eons to reach us. When Webb captures this ancient,
well-traveled light, the telescope becomes a time machine. So by gazing upon
this red blob, we are looking back more than 13.5 billion years, at a cosmic
memory.
Several astronomers I’ve spoken with say that the
preliminary discovery, if it holds true, could have extraordinary implications
for the next era of astronomy. Neither of the teams that spotted the cosmic
tomato expected to find a galaxy like this so soon, in their very first
observations of this kind. Astronomers haven’t even cranked up the Webb
telescope as far as it can go; they’ve given it a little poke, and already
distant galaxies like this one are “just falling off the tree,” Jane Rigby, a
NASA astrophysicist and the Webb operations project scientist, told me. Plus,
the galaxy appeared in a tiny field of view, smaller than a crater on the moon
in the night sky; who knows what else Webb will find in the entire moon’s worth
of sky? With each deep observation, every big rewind, the telescope will bring
us closer to the Big Bang, revealing faint galaxy after galaxy. We’re about to
go rolling through time.
The new galaxy is still only a candidate for the title of
most distant galaxy ever discovered. For one thing, the finding has yet to
undergo peer review. For another, the astronomers who spotted the galaxy in the
Webb data—two separate teams, working independently, one of which calls its
find GLASS-z13 and the other GHZ2—will need to make new observations to confirm
its distance. (I’ll call the galaxy Glassy to make things easier; the data set
that produced the discovery is known as GLASS.) But if it’s confirmed, Glassy’s
red glow would break the current record, set by a galaxy spotted through the
Hubble Space Telescope in 2015, for the most ancient light ever observed by 100
million years or so.
The teams that found Glassy have dated it by studying the
properties of its light. The universe has been expanding ever since the Big
Bang, a process that stretches light into longer, redder wavelengths. Starlight
from distant galaxies leaves its source as visible light, but by the time it
reaches us, it is “redshifted” down the electromagnetic spectrum into the
infrared range—invisible to our eyes, but perfect for Webb’s sensors.
Astronomers know that the redder light is, the farther away the galaxy that produced
it. Glassy “is detected very, very well in the redder wavelengths, but when you
go to the bluer wavelengths, it just completely drops out, and it drops out
very dramatically,” Rohan Naidu, an astronomer at Harvard who led one of the
teams that spotted the galaxy, told me. “That signature is very characteristic
of these very distant galaxies, and it’s very difficult for any other objects
to make in such a dramatic manner.”
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A zoomed-out view of Glassy |
To confirm Glassy’s distance from us, astronomers will need
to measure the galaxy’s light using a different method that would reveal
information about its chemical composition. That technique is considered the
gold standard in measuring galactic distances, and scientists are certain that
Webb can pull it off. Last week, the Webb team released data that showed just
how well the observatory can capture the particularities of a galaxy much
closer than Glassy, but still considered quite distant. The light from that
galaxy took 13.1 billion years to reach Earth, and yet Webb could pick out the
distinct signatures of oxygen, hydrogen, and neon with impressive sharpness.
Knowing the composition of the most distant galaxies “is really going to reveal
to us something fundamental about how these galaxies form and grow,” Tommaso
Treu, a UCLA astrophysicist and member of the other team that independently
identified the galaxy, told me. (Treu also led the Webb observation program
that produced the data in which Glassy was found.)