The European Space Agency (ESA) has just made public an extensive set of discoveries made by the Gaia space telescope which, since 2013, has been observing our galaxy with an unprecedented level of detail. Among them, the detection of half a million new stars belonging to the Omega Centauri star cluster, more than 380 possible gravitational lenses (a phenomenon that allows detecting very distant galaxies) and the improved position of more than 150,000 asteroids stand out.
The findings, which according to ESA go beyond the objectives for which Gaia was designed, come from the study, and in some cases the extension, of the third delivery of data that the mission generated in 2022, and complement the catalog most complete ever created of the Milky Way and already contains the positions of more than 1.8 billion stars.
Despite the precision with which Gaia can observe, there are areas of our galaxy with such a density of stars that it is almost impossible to identify them individually. This is the case of the so-called globular clusters, objects that are among the oldest in the universe and, therefore, are of great scientific interest.
In an attempt to surpass Gaia's measurement capabilities, those responsible for the mission chose Omega Centauri, the largest globular cluster that can be perceived from our planet, located about 18,300 light years away and containing nearly 10 million stars. . For the study, it was decided to use an unforeseen mode of operation to observe the area surrounding the center of the cluster, where the density of stars is a little lower.
The result has been the discovery of more than half a million new stars. The importance of the discovery not only allows us to complete the census of Gaia stars, but according to Alexey Mints, belonging to the Leibniz Institute of Astrophysics in Potsdam and one of the members of the project, it will allow us to study in detail the structure of the cluster and the movements of the stars that compose it, thus creating a large-scale map of Omega Centauri.
As a result of the success achieved with Omega Centauri, Gaia is currently studying eight other globular clusters. The study of these objects is essential to confirm the age of our galaxy and know the evolution it has undergone since its birth.
Although the mission's main objective is to map the Milky Way, Gaia has been able to detect hundreds of phenomena suspected of being gravitational lenses. In a gravitational lens, the weak light from a distant object is distorted when, to reach our instruments, it must pass through a region located in the foreground and in which a large amount of mass accumulates. This distortion increases the brightness of the object while generating multiple images of it. In this way, it is possible to detect very distant galaxies.
The new study includes 381 possible gravitational lenses corresponding to quasars, nuclei of extraordinarily distant galaxies that contain, inside, active supermassive black holes (that is, they are devouring matter).
Quasars are especially important for the study of the early universe. As Christine Ducourant, from the Bordeaux Astrophysics Laboratory (France) and member of Gaia, indicates, this finding is “a gold mine for cosmologists” and represents “the largest set of quasar candidates ever published in one go.”
Of the gravitational lenses detected by Gaia, five could correspond to the so-called Einstein crosses, a very unusual phenomenon in which the alignment between the concentration of mass in the foreground and the distant galaxy is such that four copies of it are generated in cross.
The results announced by ESA also include more precise information on 156,823 asteroids, which allows us to improve by 20 times the precision with which we know the orbit of these bodies. Gaia is expected to double the number of asteroids observed by the time it generates its fourth data delivery, scheduled towards the end of 2025.
The analysis of galactic dust is another of the studies announced by ESA. Specifically, the mission has added up to six million light spectra, which should allow astronomers to better understand the composition of the interstellar medium.
Finally, the Gaia team of scientists has analyzed in detail 10,000 red giant stars that present periodic variations in their brightness. These stars are part of the catalog generated by the third delivery of data from the mission and which contains about two million variable stars.
