Ever since the Hubble Space Telescope went into orbit in 1990, it has continued to amaze us with stunning images of the Universe. However, as with every astronomical observation instrument created since Galileo first pointed his telescope at the sky, Hubble’s observations also reveal astronomical objects that are too distant and diffuse to suggest the existence of many others that escape detection. your chances. Some of these objects leave a faint signal that scientists interpret as galaxies that, because they are so far away and glow at frequencies of infrared light that the space telescope cannot pick up, are called “Hubble’s dark galaxies.”
On December 25, 2021, the James Webb Space Telescope (JWST), the newest and most powerful space astronomical observatory to date. As has happened so many times before, the images obtained with the new instrument are impacting the scientific, and non-scientific, community. These observations are not made randomly, they have been programmed for years, and simulations had even been carried out previously in order to anticipate the possible results that the JWST. Teams of expert scientists in different disciplines and with different objectives have participated in these works. Our guest, Pablo G. Pérez González, a researcher at the Center for Astrobiology (CAB).
Once he JWST began operating, the actual images obtained proved to be of a quality that exceeded the most optimistic expectations. Knowing that the visible light emitted by galaxies and stars gradually ages over time, which translates into a drift towards the red and infrared, due to the expansion of the Universe, the designers of the James Webb telescope specially equipped it to capture the infrared light that reaches us from the most distant and oldest galaxies, which are the ones that were created at moments closest to the Big Bang.
By observing a region of the sky where galaxies were dark to Hubble, the new instrument revealed a universe teeming with galaxies that glowed brilliantly at infrared frequencies. Now, thanks to these data, Pablo G. Pérez and a large group of scientists have just published an article in the scientific journal The Astrophysical Journal Letters that shows what this universe of galaxies is like that not only went unnoticed by Hubble, but also by telescopes. more powerful terrestrial telescopes, such as the Gran Telescopio de Canarias, the Very Large Telescope or the Keck. The study is part of one of the largest international collaborations working with data from the JWSTdenominada Cosmic Evolution Early Release Science (CEERS).
What do dark galaxies look like to Hubble when observed in the light of the new JWST?
Pablo explains that three types of galaxies have been discovered that provide information that reveals unsuspected characteristics before they could be observed by James Webb.
The first type is constituted by a group of galaxies composed of aged stars in which no recent star formation is observed. They are so inactive that they are often classified as “dead galaxies.” These are huge clumps of old stars that, for some reason scientists don’t understand, have long since stopped creating new generations of stars within them.
The second type of galaxies observed with James Webb is very different from the previous one. It is made up of galaxies with a large amount of interstellar dust inside, a richness that serves as a seed for the birth of new stars. Analyzes coming from these active galaxies reveal the presence of metals (for astrophysicists, all chemical elements other than primordial hydrogen and helium are considered “metals”). It so happens that the heaviest chemical elements can only be created in the nuclear fusion furnace that feeds the heart of the stars, so their presence forces us to ask ourselves: How were these galaxies able to form so many metals? And how did these turn to dust, perhaps planets, so early in the history of the Universe?
Finally, the galaxies that make up the third type are very old, they existed when the Universe was barely a billion years old. Analysis of the light from these galaxies, collected by James Webb, reveals the existence of oxygen atoms excited at high temperatures. The light emitted by these oxygen atoms – comments Pablo G. Pérez during the interview – is particularly bright and easy to detect, compared to that emitted by other atoms such as carbon or silicon, which are created at the same time in nuclear furnaces melting inside stars. The existence of oxygen revealed by the analysis of the radiation coming from these galaxies suggests that the stars that contain it are not of the first generation, that is, they were not formed at the beginning, when only hydrogen and helium existed, but that they feed on the debris produced and dispersed by generations of stars older and closer to the Big Bang. Some stars and galaxies that, for now, have not been detected.
These discoveries, and many others that are taking place by analyzing data from the James Webb Space Telescope, are opening new windows to understanding the Universe.
I invite you to listen to Pablo Guillermo Pérez González, researcher in the Department of Astrophysics of the Center for Astrobiology (CSIC – WHILE).
References:
“CEERS Key Paper IV: A triality on the nature of HST-dark galaxies”, Pablo G. Pérez-González et al., ApJL, 946, LXX https://iopscience.iop.org/article/10.3847/2041-8213/acb3a5