At the center of our galaxy, and probably at the center of all the others, there are objects easier to name than to imagine. Supermassive black holes are millions or even billions of times the mass of the Sun, which in turn equals 330,000 Earths. Ours, the Milky Way galaxy, is relatively close, 27,000 light years away, and has as much mass as four million suns.
These objects, very different from the black holes that form when large stars run out of fuel and that only reach the tens of solar masses, hold the key to the evolution of galaxies and the universe. It is known that there is a correlation between the size of a galaxy and the black hole that inhabits it and also that the stars at the ends of a galaxy move faster the larger the central black hole, despite being outside its “jurisdiction Gravitational.
Within a decade, the European Space Agency (ESA) wants to focus two of its main scientific missions on these gargantuan objects to unravel their mysteries. The first of them, Athena (the acronym for Advanced Telescope for High Energy Astrophysics), it is the largest X-ray telescope built to date and was scheduled for launch in 2031. It is designed to capture the hottest and most energetic phenomena in the cosmos with precision unpublished and collect information to answer two fundamental questions. One has to do with the evolution of black holes in the center of galaxies. The other, in the way that ordinary matter, of which stars or human beings are made, intertwines with dark matter, much more abundant, but invisible, to form the fabric of which the cosmos is made.
ESA’s second major scientific mission for the next decade is LISA (Laser Interferometer Space Antenna), a constellation of three satellites with an unprecedented willingness to observe gravitational waves, a phenomenon Einstein theorized more than a century, but it was not first observed until 2016. When the collision between two extremely powerful objects, such as black holes at the center of two merging galaxies, occurs, the space-time fabric of the cosmos shakes like a pond at that a stone is thrown. Like the ripples in the water, they attenuate with distance and when the echo of these phenomena reaches the vicinity of our planet, they are almost imperceptible and are buried on the earth’s surface in a large number of signals of all kinds.
On Earth, experiments like Virgo and LIGO have detected the gravitational waves produced by the fusion of relatively small black holes, with only tens of times the mass of the Sun. LISA will be able to study very low frequency gravitational waves, such as those released by holes. supermassive blacks when meeting. To achieve this, its satellites will be placed in space, far from the disturbances of the Earth’s surface, in the formation of an equilateral triangle, separated by 2.5 million kilometers. As if they were buoys, three laser-linked free-falling sensors will detect tiny ripples in space-time tissue, less than the diameter of an atom.
LISA was scheduled for launch in 2034 because, given the complexity of this type of mission, ESA typically separates them for at least five years. However, the agency’s scientific officials saw an opportunity to multiply the value of the observations of Athena and LISA putting them to study the same phenomena with different senses. As if the former put sight and the latter touch, the study of the fusion of black holes through their X-ray and gravitational wave emissions would offer a much more complete view of the phenomenon.
To advance the launch of the gravitational wave observatory, it was necessary to increase the budget dedicated by ESA member countries to their space science program. That happened in late November in Seville, at the meeting of the ministers responsible for space activities in European countries. For the first time in 25 years, there was a significant increase in this item, which reached 1,671 million euros for the next five years. With the new planning, LISA would start in 2032, just one year after Athena.
The X-ray telescope will measure hundreds of thousands of black holes, some close and others farther away, but they are precisely the most remote, those that formed in the first hundreds of millions of years of the universe, those that interest those responsible of the mission. Understanding how these objects, which are a kind of engine of galaxies, were formed will also help to understand the evolution of the universe and, ultimately, to better understand the history that one day allowed our appearance on Earth. In combination with LISA, it will also try to understand why some of these galactic monsters activate and begin to gobble up the matter around them, launching intense radiation into space and turning the interior of their galaxies into active nuclei. The Milky Way, for example, is, at least for now, a sleeping galaxy, but it should not always be.
This joint work between two such different observatories will not be simple. This week in the magazine Nature AstronomyThree researchers from the University of Birmingham (United Kingdom) talked about the challenges, among others that, as befits a frontier science project, many things are unknown about the physical processes to be analyzed. In the collaboration, LISA would first detect a phenomenon such as a merger of two black holes and then arrive Athena to analyze the ultraenergetic emissions of the collision of giants. “One of the challenges for Athena will be identifying the true gravitational wave event [que detectó LISA] among hundreds of candidates in their field of vision ”, write the authors of the article. Although they warn about the difficulties of joint observation, they recognize that the opportunity to make new discoveries and observations that transform our vision of the universe is enormous.