Distant gamma-ray burst identified

A gamma-ray burst detected in December 2023 has been traced back to a supermassive black hole 8 billion light-years away, marking the farthest such source ever observed pointing its jets directly at Earth.

Observation location and source classification

The signal was detected by the LST-1 and MAGIC telescopes at the Roque de los Muchachos Observatory on La Palma, in the Canary Islands. The source, named OP 313, is classified as a blazar, a type of active galactic nucleus where a supermassive black hole consumes matter at a high rate, generating plasma jets often directed toward Earth.

Signal from the cosmic noon

OP 313 emitted its signal during the "cosmic noon," a period of intense star and galaxy formation approximately 11 billion years ago. Researchers analyzed the absorption of gamma photons by the extragalactic background light, a luminous fog accumulated by all the stars and galaxies that have ever existed.

Insights from gamma photon interactions

Some gamma photons collided with this ambient light and annihilated, giving rise to electron-positron pairs. This loss of signal provided valuable information, allowing researchers to trace back to a dense population of relativistic electrons accelerated by the plasma jet of the central black hole.

Energy transfer and cosmic significance

According to Domenico Della Volpe from the University of Geneva, these accelerated electrons transfer their energy to lower-energy photons, which are then propelled to the rank of very high-energy gamma rays. This process is referred to as a leptonic scenario.

Research collaboration and implications

Axel Arbet-Engels, also involved in the study, emphasized the significance of this phase of the cosmic noon for understanding how galaxies have evolved. The study was published in the journal Astronomy & Astrophysics and was supported by the international collaboration of the CTAO, the Cherenkov Telescope Array Observatory, which uses the LST-1, among other instruments.

Understanding early universe dynamics

This discovery could provide notable insights into how the first supermassive black holes of the universe managed to accelerate particles with such efficiency. The gamma-ray burst detected in 2023 offers a rare window into the cosmic noon, a pivotal period when the universe was undergoing intense star and galaxy formation.