Humans have long found meaning in the stars, but only recently have we begun to understand whole clusters of them–galaxies, way out in the depths of space. Some galaxies nearby, like Andromeda have been seen by the naked eye in the night sky as a dark smear. Other shimmery structures became known to us after the invention of the telescope in the 17th century, along with a debate about their nature: Were they clouds of cosmic dust within our Milky Way, or “island universes” of their own?
Not until the 1920s did humanity identify these glowing clouds as galaxies, when the astronomer Edwin Hubble (relying on the work of a lesser known astronomer, Henrietta Leavitt) found that some stars were too far away to belong to the Milky Way. And only in the mid-1990s, when a space telescope named for Hubble peeked farther into the universe than ever before, did we find the thousands of galaxies shimmering across the universe–island after island in a vast cosmic sea.
After Hubble, astronomers felt pretty confident that they understood galaxies and how nature makes them. But some new, startling developments have recently popped up, courtesy of a space telescope far more powerful than Hubble. In full operation since last summer ,, the James Webb Space Telescope has proven that galaxies were formed earlier than previously believed. Some of these galaxies are surprising large and bursting with stars. The findings have thrown scientists into a new reality in which their existing theories longer apply.
Everyone in the astronomy community knew that the Webb telescope was going to be revolutionary. Joel Leja from Penn State University told me that there was a clear list of what Webb could do to make our lives easier. But the discovery of cosmically chunky galaxies where there shouldn’t be any? It was not there. No one was looking for this.”
Instruments like Hubble and Webb are something like time machines. When the observatories look out into the depths, they’re basking in starlight that left its source eons ago, and has been traveling across the universe toward us ever since; in other words, to understand the cosmic beginning, astronomers must look for the most distant galaxies. Before Webb, scientists believed that those early, distant galaxies emerged at a leisurely pace. When hydrogen gas clouds collapsed on top of themselves, they ignited and formed the first stars. After that, gravity pulled the old orbs into galaxies.
All of this drawing together of disparate matter into massive cosmic neighborhoods was assumed to have taken at least 1 billion years. Sure, the most distant galaxy that Hubble ever spotted was unexpectedly bright for the cosmic conditions of the time, indicating a larger collection of stars than should have been possible. Astronomers weren’t too concerned about it. They expected that Webb, with its ultra-powerful infrared vision, would uncover the starter galaxies that they anticipated, and that Hubble couldn’t see.
Ha! said the shiny new telescope. Webb was just a few weeks old when astronomers ran to find the farthest galaxies. They wondered if the data might be wrong. The ancient galaxies were just too big and bright. A recalibration of Webb’s instruments soon showed that some measurements were off, making some galaxies appear more distant than they actually were, and some claims were revised. The big picture findings remained. The early universe was, somehow, bold and brash and remarkably luminous. “The objects we’re finding are as massive or larger than the Milky Way, which is astounding,” said Leja, who co-published a paper last week that identified six enormous galaxies that existed just 500 million to 700 million years after the Big Bang. One of these galaxies may have a mass 100 billion times that of our sun. Our own galaxy similarly contains many billions of stars, but it has had 13 billion years to reach its size.
For a brief moment, this new reality seemed to threaten astronomers’ fundamental understanding of the entire cosmos. If the starting point looked like that, could the standard model of cosmology–our strongest theory about the origins and composition of the universe, the one that didn’t account for what Webb found–be wrong? But astronomers now believe that the theory can accommodate the new telescope’s surprises. Recent computer simulations guided by the standard model have shown that the universe could indeed have created some of the galaxies that Webb has found. “While, on the face of it, the data don’t seem consistent with cosmological models, I think what we’re going to find is it’s not cosmology that’s the problem, but really what we understand about how galaxies formed,” Leja said.
There are many possible explanations as to why astronomers made mistakes. Scientists have never considered that early stars may have formed more quickly than they thought. Allison Kirkpatrick is an Astronomer at University of Kansas. She studies the evolution of galaxies. Ivo Labbe from Swinburne University of Technology is an astronomer who suspects black holes may play a part. They’re among the brightest objects in the universe, and they glow as cosmic matter gets sucked into them. Labbe explained to me that if you put a lot gas in a black hole it will begin outshining the whole galaxy. These black holes might make the early galaxies brighter and more star-filled. None of this will change the fact that first island universes were not as we had expected. Kirkpatrick said that even if you account for strange new phenomena, it is too large and too early to be able to predict them.
Investigating these questions will require more Webb observations, particularly the kind that yield more detailed measurements of starlight, known as spectroscopy. To confirm the existence of the strangest galaxies, astronomers will need to do more. Astronomers will need to understand their structure if these galaxies are really as big and old as they appear. With new spectroscopic data due to arrive this spring, researchers are at the forefront of this effort. This effort is soul-searching. Primordial starlight is rare and in high demand. Astronomers and theorists (those who study and explain cosmic wonders) don’t know what they will find. “It’s probably going to be something like five years until we’ve totally settled into our new universe that we’ve gotten from JWST,” Wren Suess, an astronomer at UC Santa Cruz and Stanford, told me.
In one sense, these new discoveries have injected drama, even anxiety, into a field that was quite stable. “It’s incredible how the universe is just so much weirder than we thought it was,” Erica Nelson, an astronomer at the University of Colorado at Boulder, told me. It’s also fun in another way. Kirkpatrick laughed with delight when I asked her if she felt stressed by the uncertain landscape that her job presents. She said, “It’s just the beginning of all things!” “It’s not going to affect my life, so it’s really fun to think about this kind of stuff.”
As I’ve talked with astronomers about what Webb has found so far, one word keeps coming up: shouldn’t. Galaxies shouldn’t be this way; the cosmic dawn shouldn’t be that way. I find these shouldn’ts delightful. They hint at the well-intentioned hubris of humans, especially the most curious ones, those who wish to determine exactly how something works and why. But of course the universe says, speaking to us by way of a giant telescope floating a million miles from Earth, This is how it is. This is, apparently, how it has always been. We’re just discovering the wonder of it now.
The post The Webb Telescope Is Scrambling the Story of the Universe appeared first on The Atlantic.
