How can we explain the bursts of X-ray emission seen from the black hole at the center of our galaxy? A team of scientists, led by Alexis Andrés, tried to look for explanations, but found that the answer is more complex than expected.
We know that at the center of our galaxy, the Milky Way, there is a supermassive black hole — generally called Sagittarius A* — with more than 4 million times the mass of the Sun. This discovery was even awarded the Nobel Prize in Physics. in 2020.
However, we also observe that the black hole occasionally emits large amounts of X-rays. These emissions are associated with the enormous energy found by material around Sagittarius A*, but their exact physical origin is still unknown.
Scientists then tried to analyze observational data from the Swift space telescope, which is capable of detecting X-rays, obtained over 15 years. Nathalie Degenaar, from the University of Amsterdam (Advisor of Andrés during his summer studies in the Netherlands) has maintained the project with the telescope for a long time, ensuring its permanence with the aim of creating a long-term database.
With so much data, the team expected to find some periodicity in the outbreaks. However, even using advanced statistical techniques, the scientists could not determine any regularity in the emissions. Outbreaks were strongest between 2006 and 2008, and again after 2012, with a milder period between 2008 and 2012.
The predicted periodicity could favor one or another model of X-ray production, such as the black hole gulping down passing material, or the black hole’s interaction with clouds of magnetized gas. However, the observed irregularity does not allow us to rule out any model yet. The mystery remains.
Cataloged data and the democratization of science
An interesting detail of the project is that Andrés is from Salvador, a country with little scientific tradition. He had the opportunity to work in Amsterdam for a summer, and is now pursuing his master’s degree at the National Autonomous University of Mexico.
The data used by him are publicly available, which favors the democratization of the study of the universe. After all, countries like the United States, France and Germany can invest in new instruments that are responsible for much of the scientific advances in astronomy.
On the other hand, the construction of large databases allows new discoveries by researchers from countries with less investment capacity — such as El Salvador and, on a different scale, Brazil.
Andrés says he wants to become a professional scientist and return to his country to grow the field. I hope the plans work out!