An international research team led by Professor Ken-ichi Tadaki of Hokkai-Gakuen University has made a groundbreaking discovery using the Atacama Large Millimeter/Submillimeter Array (ALMA).

The team has captured unprecedented high-resolution radio signals from hot gas surrounding a supermassive black hole located 12.9 billion light-years away. This innovative observation technique promises to reveal hidden black holes that formed during the universe’s early stages.

The research team observed a supermassive black hole that existed in the universe 12.9 billion years ago, with a mass exceeding one billion times that of the Sun. Quasars are among the brightest objects in the universe, powered by supermassive black holes that generate intense energy as they consume surrounding matter.

Examining the innermost regions of distant quasars has remained challenging despite their brightness, In this breakthrough study, researchers focused on radio signals emitted by highly energized carbon monoxide (CO) molecules. Their ultra-high-resolution observations revealed, for the first time, the heating mechanisms affecting gas within just a few hundred light-years of the black hole. 

Detecting strong CO emissions at high energy levels indicates extraordinarily hot gas conditions around the black hole. While ultraviolet radiation from newly formed stars typically heats gas in star-forming regions, the extreme conditions observed cannot be explained by stellar activity alone.

The research points to powerful X-rays emanating from the black hole’s accretion disk and corona as the primary heating source. These X-rays can elevate gas temperatures far beyond levels observed in typical star-forming regions.

Additionally, the team found evidence that powerful quasar winds and shock waves further contribute to this extreme heating, demonstrating that the central quasar region represents one of the most dynamic environments in the cosmos. 

This discovery has significant implications for our understanding of black hole populations in the early Universe. Quasars oriented with relatively clear sightlines appear exceptionally bright in visible light and X-rays.

However, if the quasar is viewed through a much thicker layer of cosmic dust, visible light and X-rays can be blocked, causing it to remain “hidden.”

In other words, many supermassive black holes may lie concealed within dusty regions of the early universe, simply undetected. Because the radio waves observed by ALMA are not easily absorbed by dust, this technique becomes a powerful tool for discovering such “hidden supermassive black holes.”

By applying similar high-resolution observations of energetic CO emissions to other objects, researchers expect to develop a more comprehensive census of early supermassive black holes and gain crucial insights into their formation and evolution. 

These research findings were published online in Nature Astronomy: Tadaki et al., “Warm Gas in the Vicinity of a Supermassive Black Hole 13 Billion Years Ago” (DOI: 10.1038/s41550-025-02505-x).