Universe: the mystery of small red dots in space that baffles astronomers

And because of their characteristics, it seems that they are some small galaxies3% the size of the Milky Way, but they contain billions of stars.

It could also be a galaxies that host large black holeswith a formation that had not been seen in the closest galaxies known until now.

It all depends on how these astrophysical objects are observed.

Some experts have even compared their changing appearance to mimic octopuses, a species that can take on the color and shape of other marine animals to camouflage themselves.

They are some “masters of disguise”as astrophysicist Fabio Pacucci, from the US Smithsonian Institution, says.

The small red dots “come from such distant distances that they look very faint,” Chilean astronomer Mario Hamuy explains to BBC Mundo.

“They have typical sizes of about 3,000 light years in diameter, 3% of the diameter of the Milky Way, for example, and they have a very red color, which is due to the fact that the light they emit has been strongly reddened by the presence of grains of dust in their surroundings,” he adds.

Unlike home telescopes, large observatories like the James Webb can perceive light from objects very far away in the universe. The energy signals they receive can be captured at different frequencies, which are analyzed in spectra.

When James Webb focused on the farthest points of the universe, he found these signals from the “little red dots,” that had characteristics of astrophysical objects different from those seen before.

Depending on how you view them on the spectrum, they have one of two characteristics that divide scientists.

“All light sources in the universe change their appearance when you observe them in different windows of the electromagnetic spectrum. In the same way as if you take an image of your hand in x-ray or optical light. In the first case you will see the bones of the hand and in the second you will see the skin,” explains Hamuy.

“The small red dots are no exception. Depending on which spectrum window you use, you will see different internal regions of the object”, he adds.

Like other objects in the early universe, these dots existed billions of years ago, and telescopes like the James Webb are detecting the light that has since traveled through space.

This is how scientists saw in these small red dots features like those of a galaxy that houses millions of stars with one of the spectrum analyses, but with another a galaxy with a supermassive black hole.

“We do not see these types of galaxies in our nearby universe. So it was something that arose in that early period, that lasted for a certain amount of time and that we don’t see now,” astrophysicist Begoña Vila, a NASA instrument engineer, explains to BBC Mundo.

“As soon as they began to be observed, at first it was thought that they were another type of object. But Now we know that they are galaxies and it is super exciting for everyone”, he adds.

Given how different these objects are from the early universe and because they are “masters of disguise,” they are challenging the models that scientists have built to explain the origin of galaxies.

Part of what is surprising about these objects, explains Vila, is that it is not known how they could have so many stars – a number perhaps similar to those found in the Milky Way. in such a small space, astronomically speaking.

“How so many stars formed so quickly is a question,” he says.

Pacucci explains that in these galaxies there would be so many stars in such a small space that it is as if the entire population of China was placed in one room.

This leads to the question of 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.

“The models that exist about the formation of galaxies For now they explain very well what we have around us, the nearby galaxies, but they are already indicating that they need modifications for this early universe, for these galaxies,” says Vela.

Likewise, if the little red dots are actually galaxies hosting a supermassive black hole, scientists’ understanding of how they form would have to be rethought. Although not to a level that changes the great theories, Vila clarifies.

“(At first) it seemed that the cosmology had been broken and it was thought that it had to be changed. But it wasn’t 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 we knew and reflected what we know until now. But clearly This early universe has surprises and that’s what Webb was designed for”.

Since the small red dots were identified and their striking change in appearance was discovered, scientists have continued their studies with new models and instruments to observe them and try to understand what they are about.

It is hoped that in the coming years, researchers will have a theory that can explain what they are and how they were formed..

For Vila, perhaps the most appropriate answer is not to define whether they are galaxies with millions of stars or supermassive black holes: “It can be a little bit of both theories.”

But this will also allow scientists to learn more about the formation of the universe from stages that, until before the launch of the James Webb space telescope, had less data.

“The most surprising thing is that the small red dots are very abundant. If they were active galaxies, they would exceed the quasars (very heavy galaxies) detected by traditional methods by a factor of 10,” says Hamuy.

And he adds: “In any scenario, the small red dots are crucial to understanding the early formation of galaxies“.

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