photo caption, The James Webb space telescope has detected signs of mysterious astrophysical objects from the earliest ages of the universe
1 October 2024
The telescope found signs of objects in space that formed 12 billion years ago — soon after the Big Bang, which happened 13.8 billion years ago.
These are objects that have never been detected before and challenge what science knows about how galaxies form.
Because of their brightness in the red spectrum of the instruments used to observe them, astronomers named the objects “little red dots.” But defining what they are is creating a debate among scientists.
They look like small galaxies, about 3% the size of the Milky Way — but containing billions of stars.
They could also be galaxies with a large number of black holes, a formation never before observed in the nearest known galaxies.
It all depends on how these astrophysical objects are observed.
Some experts even compare the change in appearance to a species of octopus that can change its color and shape to camouflage itself.
They are “masters in disguise”, says astrophysicist Fabio Pacucci, from the Smithsonian Institution, in the United States.
Change appearance
The small red dots “come from such great distances that they come here very faintly”, explains astronomer Mario Hamuy, professor at the University of Chile to BBC News Mundo.
“They are typically 3,000 light-years across, about 3% of the diameter of the Milky Way, for example, and have a very reddish color, which is because the light they emit has been greatly altered by the presence of a grain of dust. around you.”
credit, JWST/NIRspec
photo caption, The small red dots are analyzed using the spectrum of light generated by observations from the James Webb telescope
Unlike household telescopes, large telescopes such as the James Webb can capture light from very distant objects in the universe. The energy signals it receives can be captured at different frequencies, which are analyzed in spectra.
When James Webb focused on the most distant points in the universe, he came across signs of “little red dots”, which had different characteristics from previously known astrophysical objects.
Depending on how you look at the spectrum, they have characteristics that divide scientists.
“All light sources in the universe change their appearance when you look at them in different windows of the electromagnetic spectrum. In the same way that happens when you make an image with X-rays or with light from your hand. In the first case, you will see you the bones of the hand, and in the second you will see the skin”, explains Hamuy.
“The little red dots are no exception. Depending on the spectral window you use, you will see distinct inner regions of the object,” he says.
Like other objects from the beginning of the universe, these dots existed billions of years ago. Telescopes such as the James Webb detect light that has traveled through space since then.
Due to these differences in spectrum analysis, scientists saw that these small red dots have different characteristics: sometimes like a galaxy with millions of stars, sometimes like a galaxy with a supermassive black hole.
“We do not see this type of galaxies in our nearby Universe. It was what was visible at that time at the beginning of the universe, which lasted for a certain time and which we no longer see,” astrophysicist Begoña Vila, instrument engineer, BBC News Mundo said from NASA.
“When we started looking at them, at first we thought they were something else. But now we know they are galaxies and that’s amazing for everyone.”
Because they are different and because they are “masters in disguise”, the objects are challenging the models that scientists have built to explain the origin of galaxies.
Rethink what we know
The surprising thing about these objects, explains Vila, is that it is not known how they could contain so many stars – a number perhaps similar to that of the Milky Way – in such a small space, astronomically.
“It’s a question of how many stars formed so quickly,” he says.
Pacucci explains that there would be so many stars in these galaxies in such a small space that it would be like putting the entire population of China in one room.
This is the result of the question whether the models that scientists have to explain the formation and composition of galaxies in the early stages of the formation of the universe are correct.
“Current models of galaxy formation explain very well what is around us, the nearby galaxies, but there are already signs that they need modifications to explain this primordial universe, these galaxies”, says Vela.
credit, NASA/ESA/CSA/STSCI/BRANT ROBERTSON ET AL
photo caption, Primary galaxies, like JADES-GS-z14-0, are generating new information about the formation of the universe
Similarly, if the small red dots are galaxies with a supermassive black hole, scientists’ understanding of how they form must be reconsidered. But not on a level that changes the major theories, explains Vila.
“(At first) it seemed that the cosmology was broken and it was thought that it had to be changed. But it was not like that. The Big Bang is still perfect, there are no problems”, says the NASA expert.
“What happens is that the models that we had until now were based on the data that we knew and they showed what we knew so far. But it is clear that the early -this universe and that’s what James Webb was designed to do.”
What happens now?
Since the discovery of the small red dots and their change in appearance, scientists are continuing their studies with new models and instruments to observe them.
Hopefully in the coming years researchers will have a theory that can explain what they are and how they formed.
For Vila, the most appropriate answer may not be to define whether they are galaxies with millions of stars or supermassive black holes: “It could be a bit of both theories.”
But this will also allow scientists to learn more about the formation of the universe from stages — until before the launch of the James Webb Space Telescope — that little was known about.
“What surprised him the most is that the little red dots are very abundant. If they were active galaxies, they would be bigger than quasars [galáxias muito pesadas] detected by traditional methods by a factor of ten”, says Hamuy.
He says: “In either case, the little red dots are crucial to understanding the early formation of galaxies.”