The Fermi Gamma-Ray Space Telescope celebrates its 15th anniversary

• • Fermi LAT has revolutionized the field of high-energy astrophysics and has provided us with a new window of exploration into the most violent universe, allowing us to better understand the physical processes and extreme conditions that exist in the cosmos.

This week marks an important milestone in space exploration in general and, more specifically, in the field of particle astrophysics or astroparticles, as we celebrate the 15th anniversary of the launch of NASA's Fermi satellite, which was put into orbit on June 11, 2008. Fermi carries two instruments on board, the Gamma-ray Burst Monitor (GBM) and the Large Area Telescope (LAT). The Institute for Theoretical Physics (IFT UAM/CSIC), through researcher Miguel A. Sánchez-Conde and his group, has been part of the Fermi-LAT Collaboration since 2017.

The Universe hosts numerous exotic events, some of which can generate unimaginable amounts of energy. Supermassive black holes, neutron stars, supernova explosions... These are just some of the phenomena that generate gamma radiation, the most energetic form of radiation, billions of times more energetic than the type of visible light for our eyes. What physical phenomena occur to produce so much energy? What happens in the vicinity of these phenomena? How does the study of these energetic objects contribute to our understanding of the very nature of the Universe, its composition, and behavior?

During its fifteen years of uninterrupted operations, the Fermi gamma-ray space telescope has revolutionized the field of high-energy astrophysics and has helped us answer these and many other questions. Not in vain, Fermi's detection of high-energy gamma rays from cosmic sources has provided a new window of exploration into the most violent Universe, allowing us to better understand the physical processes and extreme conditions that exist in the cosmos.

With Fermi, astrophysicists have had a powerful ally over the past 15 years to study particles moving at relativistic speeds in the Universe, with energies much higher than those observed in terrestrial particle accelerators. Fermi has exceeded all expectations, providing a wealth of data and revolutionary scientific discoveries. Thanks to Fermi, we have been able to create the most precise map of the gamma-ray sky to date, which has led to the discovery of thousands of objects that emit this type of radiation, both inside and outside our galaxy. In fact, Fermi has unveiled in this energy domain an unexpected and furious cosmic "bestiary" full of surprises: insatiable supermassive black holes dwelling at the centers of almost all galaxies, colossal star explosions with dozens of times the mass of our Sun, neutron stars acting like black widows in binary star systems...

One of Fermi's most notable achievements has been the study of gamma-ray bursts (GRBs), cosmic explosions where immense energy is released. These bursts, which can be a billion times brighter than any other source in the sky, are cataclysmic events that occur in distant galaxies. In addition to gamma-ray bursts, Fermi is also instrumental in the study of pulsars, black holes, dark matter searches, and other key areas of particle astrophysics. Currently, Fermi is also crucial for studying gamma-ray transient phenomena (with variable flux and duration) and for the search of electromagnetic counterparts of gravitational wave events, being the only instrument currently in operation that monitors the entire sky in this energy domain every few hours.

The IFT UAM/CSIC has been a key collaborator in the operation and development of Fermi LAT's scientific mission over the years. IFT researchers have played a prominent role in data analysis and interpretation of the results obtained, particularly in the context of gamma-ray searches for dark matter, leading or co-leading much of the work done on this topic to date within the Fermi-LAT Collaboration. Likewise, the international working group on dark matter and exotic physics within that collaboration has been coordinated from the IFT for several years, and more recently, the principal investigator of the IFT node in Fermi LAT has taken on the role of deputy coordinator for all the science currently being conducted with Fermi LAT.

IFT researchers and their collaborators will continue to use Fermi satellite data to unravel the mysteries of the Universe in the gamma-ray domain and will undoubtedly continue to contribute to future missions in the field of particle astrophysics.

Happy birthday, Fermi!