At a distance of nearly 33 billion light-years from Earth, the powerful James Webb telescope has discovered some of the most distant and oldest galaxies ever discovered. And they turn out – quite surprisingly – to be much larger than other galaxies previously found at such extremely large distances.
Researchers write this in the magazine The Astrophysical Journal Letters. For the study, they used observations from the James Webb telescope, which was designed, among other things, to observe the first – and therefore also the most distant – galaxies in the universe. “Very little is known about the early universe,” says researcher Bingjie Wang. “And the only way to learn more about that period and test our theories about the formation of the first galaxies is to look at these distant galaxies. Prior to our research, we only knew of three galaxies that were at such an extreme distance.” And now researchers can add two more copies. One will now go down as the second-farthest galaxy ever observed. The other must tolerate three more distant galaxies in front of it.
13.4 billion years on the road
Because the light from these galaxies took billions of years to reach James Webb, the telescope now sees them as they looked 330 million years after the Big Bang, or 13.4 billion years ago. “The light from these galaxies is old, about three times older than Earth,” explains researcher Joel Leja.
33 billion light years away
You might expect that the galaxies would now be about 13.4 billion light years away (a light year is the distance that light travels in one year), but that is not the case. Due to the expansion of the universe, they are now about 33 billion light years away, the researchers explain.
Of course it is always special to see such distant galaxies. But what makes these two extra special is that they are quite large. One of them would even be at least six times larger than the three galaxies previously discovered at a comparably large distance from Earth. The galaxy in question would be about 2,000 light-years wide. This makes it much smaller than our Milky Way – which measures about 100,000 light years – but remarkably large for the time in which it was formed. It is assumed that the early universe was much more compressed and that galaxies could therefore not grow so large.
But the two galaxies that researchers have now discovered are quite large. We also see this in James Webb’s recordings. While the three galaxies previously discovered at such a great distance from Earth only formed red dots on James Webb’s images, the situation is very different for these two galaxies. The second-farthest galaxy ever (also referred to as UNCOVER Z-13) looks most like a kind of fluffy ball in the images. And the fourth-distant galaxy (UNCOVER Z-12) is shaped much like a peanut. “It is unclear whether the difference in size is related to how the stars formed or what happened to them after they formed,” Wang said. “But the diversity of properties within these galaxies is surprising. We expect these early galaxies to have formed from similar materials, and yet they are all very different.”
The two large galaxies were discovered in a part of the universe also referred to as Pandora’s Cluster or Abell 2744. What makes Pandora’s Cluster so interesting for research into early galaxies is that it is located behind several clusters of galaxies. And those clusters serve as a gravitational lens: with their gravity they bend and amplify the light from much more distant objects. And so the clusters help to make visible even galaxies billions of light years away. “That enormous ‘lens’ in space allows us to look very deeply into the universe, but only at a very small part of the universe,” Leja explains. And then you just have to be lucky that you come across very distant – and therefore old – galaxies. “But we were lucky and discovered two ancient galaxies. It is unbelievable.”
An analysis of the light emitted by the two ancient and larger galaxies reveals that they were growing rapidly, forming stars very actively and being poor in heavier elements (such as metals). The fact that they do not contain any heavy elements fits neatly in line with expectations. Heavy elements are formed in the cores of stars and were first released when the first stars died. “It makes sense that these early galaxies did not have heavy elements, such as metals, because they were the very first factories in which these heavy elements could be built,” Leja explains.
Now that more and more distant and therefore old galaxies are being discovered, you can of course wonder whether we really already have the very first galaxies in our sights or whether there are even older galaxies waiting to be discovered. The researchers expect that, with a little help from gravitational lenses and the powerful infrared instruments on board James Webb, it should certainly be possible to discover even more distant galaxies. However, the big question remains whether they even exist. We won’t know until we find them. Astronomers will therefore continue to search in the near future.