More than a hundred scientists, including some Spaniards, have teamed up to detect the elusive extragalactic background light or EBL (acronym in English forextragalactic background light). Its aboutset of photons generated by all the stars and black holes in the universe, and from which the oldest stellar emissions can be deduced. The study has been prepared with data from theFermi gamma ray space telescope.
? The light from the first massive stars to ever shine in the universe is included in the EBL, but since we have a fairly good understanding of the rest – of the “normal” stars that we can see, for example, with optical telescopes – we are able to to restrict the light of the former ?, has explained to the SINC agency Marco Ajello, of the Deutsches Elektronen Synchrotron DESY (Germany) and main author of the work that publishesScience.
The team has had to overcome the fact that photons in the extragalactic background light cannot be observed directly, as they are confused with the foreground emissions from our solar system and galaxies. The solution has been to locate them indirectly, with the help of the most numerous sources of gamma rays: the blazars, which are nothing more than very active galactic nuclei with a central supermassive black hole. “We have used the blazars as ‘cosmic beacons’ so that by analyzing how gamma rays are attenuated due to EBL ‘fog’, we can quantify how much extragalactic background light there is between us and those distant objects,” Ajello notes. “As blazars are distributed throughout the universe, we can measure the EBL at different times,” he adds.
In this way, scientists have been able to better characterize the EBL within the spectrum of light (redshift), as well as the rate of formation of the first generation of stars. With this data they trust in being ablebetter understand the nature of star formation and the evolution of galaxies.
