The James Webb Space Telescope, which was developed the US, Canadian and European space agencies and opened its eyes to the sky in July 2022, has delivered on its promise.
In particular, scientists hoped that it would be able to peer back in time to view the early history of our universe.
The space observatory revealed six massive galaxies that existed between 500 million and 700 million years after the big bang that created the universe.
One of its latest data harvests, published by NASA on February 22, takes us back to between 500 and 700 million years after the Big Bang with images of 13 galaxies, six of which are particularly massive.
They are not among the most distant galaxies identified by the telescope, but their very existence raises questions because they cannot be explained by the standard cosmic model for galactic formation.
According to the existing theory, early in the history of the universe, there should not have been enough matter to ignite so many stars.
“Two of these galaxies had already been spotted, barely, by the Hubble telescope in 2012, but the others are new. Their large mass was unexpected and is a reason for us to publicize them. We were mind-blown, kind of incredulous,” said Ivo Labbé of Swinburne University of Technology in Melbourne, Australia, the spokesperson for an international team of 11 members, mostly from the United States.
Six of these newly discovered galaxies exceed the mass of 10 billion suns, and one of them even exceeds 100 billion, which brings it closer to our Milky Way, but 30 times more compact and with only a few tens of millions of years of existence.
Until now, such monsters had only been seen beyond one billion years after the Big Bang.
On the images, which were some of the first to be captured by the telescope in July, these giants don’t seem particularly impressive – nothing but small, blurry, reddish points on a black background.
At such distances, about 13 billion light-years from us, it is impossible to make out the stars within them, or even their spiral or elliptical shape, which the Webb Telescope is able to see in galaxies more in our cosmic neighborhood.
But the intensity and colors of these pixelated spots allow us to determine the distance and mass of these objects.
Of course, the universe is not fixed. These galaxies are moving away from us and the light that reaches us shifts in color, like when the sound of a siren is perceived as dropping in pitch after passing by, due to the Doppler effect.
Astronomers calculate the shift of a theoretical spectrum based on the received spectrum to deduce the distance. More precisely, they rely on two particular color signatures, one related to young stars, and the other, to older stars.
“With these two signatures, we remove ambiguities to estimate the distance. And, by focusing on older stars, we limit ourselves to candidates that are necessarily more massive,” Labbé explained.
Labbe said he and his team didn’t think the results were real at first — that there couldn’t be galaxies as mature as our own Milky Way so early in time — and they still need to be confirmed. The objects appeared so big and bright that some members of the team thought they had made a mistake.
“We were mind-blown, kind of incredulous,” Labbe said.
The Pennsylvania State University’s Joel Leja, who took part in the study, calls them “universe breakers.”
“The revelation that massive galaxy formation began extremely early in the history of the universe upends what many of us had thought was settled science,” Leja said in a statement. “It turns out we found something so unexpected it actually creates problems for science. It calls the whole picture of early galaxy formation into question.”
These galaxy observations were among the first data set that came from the $10 billion Webb telescope, launched just over a year ago. NASA and the European Space Agency’s Webb is considered the successor to the Hubble Space Telescope, coming up on the 33rd anniversary of its launch.
Unlike Hubble, the bigger and more powerful Webb can peer through clouds of dust with its infrared vision and discover galaxies previously unseen. Scientists hope to eventually observe the first stars and galaxies formed following the creation of the universe 13.8 billion years ago.
The researchers still are awaiting official confirmation through sensitive spectroscopy, careful to call these candidate massive galaxies for now. Leja said it’s possible that a few of the objects might not be galaxies, but obscured supermassive black holes.
While some may prove to be smaller, “odds are good at least some of them will turn out to be” galactic giants, Labbe said. “The next year will tell us.”
One early lesson from Webb is “to let go of your expectations and be ready to be surprised,” he said.