A distant galaxy (indicated with an arrow) shows signs of reionisation only 330 million years after the Big Bang. Credit: Esa/Webb, NASA & CSA, Jodes Collaboration, J. Witstok, P. Jakobsen, M. Zamani (ESA/Webb)
Since he started collecting data, the James Webb Space Telescope (JWST) has shed light on the first universe, helping us to better understand the temporal sequence of the events that led to our modern cosmos.
In an article published on March 26 in Nature, A team led by the University of Copenhagen reports to find a galaxy right in a crucial moment in the initial universe known as the era of reionisation.
Transforming the transparent cosmos
The young universe was full of neutral hydrogen, which acts like a fog and absorbs the light, preventing it from traveling very far. During the era of reionisation, the ultraviolet energy light (UV) flooded the cosmos; Where he met hydrogen, the light eliminated the electrons of the atoms and brought the gas from a neutral state to one excited. Over the course of hundreds of millions of years, this has made the universe transparent to light, allowing us to see through vast distances and far in time since then.
But the cause of this transformation – that is, the source of UV light – has long been an open question. The astronomers theorized it came from the first generation of galaxies. Now, JWST’s ability to see some of the first galaxies never found is helping astronomers to restrict the possibilities.
Black stars and holes
The team of the University of Copenhagen has identified a young galaxy called Jodes-Gs-Z13-1-the at a time when the universe was only 330 million years old. The main author of the Joris Witstok studio, a post -Entrance member at the Dawn Cosmic Center of the University of Copenhagen, says that although it is not the farthest galaxy ever seen, currently classified fifth, it is the first (for example, the first) galaxy seen in the reionisation process.
JWST data show that Jades-Gs-Z13-1-The radiation is emitting in a small range of UV wavelengths, called Lyman-Alpha Light. Lyman-Alpha wavelengths are particularly sensitive to the absorption by hydrogen neutral, directing astronomers to the fact that there is not very little inside and around this galaxy.
A possible source of Lyman-ALPHA light could be the stars of Jodes-Gs-Z13-1-The. As the first galaxy, it is full of formation of stars and could host a specific type of stars present only in the young universe: some of the greatest stars ever born, called population of the III population. However, Witstok says that the stars of the galaxy could also be stars “simply very hot and huge” that are not specifically of the population of the III population, but those that arrived a little later, after that generation of alone has become extinct.
“The theoretical models suggest that the stars of the population III, which are made of pure hydrogen and helium, should be even more enormous and warmer than the type or B stars that we see around us today”, says Witstok. “This is because they are not able to refresh themselves [in the same way] As “normal” stars that already contain some heavier elements (such as carbon, oxygen, etc.). “
This lack of cooling could make the stars of the III population extremely hot. And consequently, they could have generated a fairly energetic light to excite the hydrogen neutral and cause reionisation inside and around the galaxies – and eventually throughout the universe.
But the UV signature issued by Jades-Gs-Z13-1-The could also come from an accumulating central black hole, which would be surrounded by such a hot plasma disc that also that it could trigger the enough energy radiation as to cause reionisation. If it is a black hole, it would be one of the first views and will inform us about the formation of the galaxy in the first universe. It would also support the models that suggest the accumulation of supermassichi black holes, called active galactic nuclei, have caused cosmic reionisation rather than the stars.
A candle in the dark
Jades-Gs-Z13-1-The hot photons is losing to excite the hydrogen beyond the limits of the galaxy and in the intergalactic medium, creating an ionized (transparent) bubble of about 650,000 light years. This bubble is like a candle that lights up a little vast darkness around it.
Regardless of the Lyman-Alpha Light source of Jodes-Gs-Z13-1-La, the discovery helps to further limit the start of reionisation and gives us a sign for JWST’s future observations, since JWST is the only large quite large telescope and with the range of right wavelengths to capture galaxies so far with many details.
Of the four known galaxies more distant than Jades-Gs-Z13-1-The, as well as 10 to 15 that are at similar distances, says Witstok, as mentioned, nobody shows the same signature Lyman-ALPHA, so there is not much to compare it again.
“The search for new candidates is in progress, so we hope to find other examples in the near future,” says Witstok.
