Two articles – one published in the journal “Nature Astronomy” and one in “The Astrophysical Journal Letters” – report different aspects of a study of the blazar cataloged as VLASS J041009.05−013919.88, or simply J0410−0139, the most distant found so far. Two teams of researchers used several space and ground-based telescopes and some radio telescopes to obtain detections in various electromagnetic bands.

This combination of observations allowed a systematic search for active galactic nuclei to be conducted and the consequent identification of J0410−0139, a quasar of the type pointed toward the Earth that is called a blazar. About 12.9 billion light-years away, it could be just one of many quasars dating back to the epoch of reionization, a crucial period in the history of the universe in which hydrogen, which was originally neutral, was separated into protons and electrons. Neutral hydrogen blocked light, so reionization transformed the universe from a dark place to a bright one thanks to the light of primordial stars.

Detecting quasars from such a remote era is truly difficult even for the most powerful instruments available to astronomers. For this reason, the authors of the two studies combined infrared observations with the New Technology Telescope (NTT) and the Large Binocular Telescope (LBT), one of the Keck telescopes, and the Magellan telescope, spectroscopy with the Very Large Telescope (VLT), X-rays with the ESA’s XMM-Newton and NASA’s Chandra space telescopes, and radio observations with the ALMA, NOEMA, and VLA radio telescopes.

The result of this large observation campaign in various electromagnetic bands led to the confirmation that J0410−0139 is a blazar about 12.9 billion light-years from Earth. According to Eduardo Bañados, who led the various aspects of this study, the fact that a quasar so far away is pointed toward Earth suggests that there could be many others whose jets go in other directions.

This discovery is important for understanding how the supermassive black holes that power these quasars influenced the evolution of the universe. Astronomers think that black holes with jets can grow much more quickly than those that don’t have jets, so finding other primordial quasars like J0410−0139 would help verify this.

The study of the blazar J0410−0139 may also be important because the analysis of the absorption lines generated by the matter encountered by its light could allow to study the signals generated by neutral hydrogen. Supermassive black holes are among the candidates, along with stars, for the ionization of primordial hydrogen. This means that this is a way to study reionization and the processes that made the universe what we can see today.