LST-1 Telescope Makes First Scientific Discovery

Posted on December 31, 2023 • 3 minutes • 428 words

Active galaxies are galaxies whose cores emit a large amount of energy due to processes occurring around their supermassive black hole. Quasars are one type of active galactic nucleus. It is rare to be able to detect them in the high-energy range, because the matter of the accretion disk weakens the high-energy radiation: photons with the highest energies are best absorbed. In addition, the further the object, the greater the influence of the extragalactic background light (EBL) on its high-energy radiation, ‘flying’ to us. Extragalactic background light is the total radiation of objects beyond our Milky Way galaxy.

The LST-1 telescope observes in the range from 20 to 150 gigaelectronvolts, in which high-energy streams are less affected by background light. At the beginning of the month, on December 1, 2023, astronomers working with the LAT telescope as part of the Fermi gamma-ray telescope reported a change in the activity of the OP 313 source - its gamma radiation increased. Over the course of four days, from December 10 to 14, the LST-1 telescope observed the object. Scientists caught radiation of over 100 gigaelectronvolts. That is, the energy of these photons is a billion times higher than the energy of the visible light to us. So OP 313 became the tenth in the list of known high-energy quasars. Moreover, with a redshift of 0.997, it is also the most distant similar object and the second farthest source of high-energy radiation. A redshift of 0.997 means that the light from this quasar traveled to us about eight billion years ago.

Even more importantly not the discovery itself, but the fact that the LST-1 telescope, which is now being put into operation, has proven its efficiency. This is a prototype of the Large-Sized Telescope (LST), one of the three types of telescopes in the Cherenkov Telescope Array - an international project to create a new generation of instruments for the study of gamma radiation in a large range. Some of them will be located in the Northern Hemisphere, some in the Southern Hemisphere. The LST-1 prototype is a ‘representative’ of the northern group of telescopes, with the help of which astronomers will primarily search for extragalactic objects of low energies. Upon completion of the commissioning, it will become the first in the Cherenkov Telescope Array. In addition to high sensitivity, an important feature of these telescopes is their agility. They can change position in less than 20 seconds, allowing for the study of transient events, such as gamma-ray bursts. This means that a whole series of new discoveries can be expected.