First Observation of a Galactic Black Hole's Breathing Using ALMA and Chandra

A long-standing mystery in astronomy has been solved through the collaboration of telescopes in the Chilean desert and in Earth orbit. By combining five years of high-resolution observation data from ALMA (Atacama Large Millimeter/submillimeter Array) in Chile with data from NASA’s Chandra X-ray Observatory, scientists have for the first time clearly captured a hot gas outflow from the supermassive black hole at the center of our galaxy, “Sgr A*” (Sagittarius A*). This result was announced on June 6, 2026, via a press release from the U.S. National Radio Astronomy Observatory (NRAO).

Core of the Discovery

The research team observed signals from carbon monoxide (CO) molecules within a region about three light-years around Sgr A*. CO is a key tracer for cold molecular gas, and by mapping its distribution in detail, the gas structure around the black hole can be visualized.

Observations revealed a large cone-shaped cavity within the distribution of cold gas. The apex of this cavity points toward the black hole, and its shape suggests that the cold gas has been pushed aside by a hot gas flow. Furthermore, when superimposed with data from the Chandra X-ray Observatory, it was confirmed that the interior of this cavity is filled with extremely hot thermal gas. This is evidence that Sgr A* continuously emits a hot, high-energy flow that pushes aside or heats the surrounding cold gas.

This outflow is not as powerful as the intense jets seen in active galactic nuclei. However, it is estimated to have persisted for at least approximately 20,000 years. This phenomenon, as if the black hole is “breathing,” had been predicted theoretically, but direct observation had been difficult until now. This discovery puts an end to a mystery that has perplexed the astronomical community for more than 50 years.

Breakthrough Brought by Advances in

Observation Technology

Why was this observation successful for the first time now? The key lies in ALMA’s improved performance and long-term observations. ALMA is an interferometer that links 66 antennas, achieving remarkable resolution in the millimeter and submillimeter wavebands. The accumulation of high-resolution observation data over five years, reducing noise to the point where faint signals from CO molecules could be statistically detected, made this discovery possible.

Additionally, the multi-wavelength collaboration with Chandra’s X-ray data was decisive. The method of capturing the structure of cold gas with radio waves and confirming the presence of hot gas with X-rays is an excellent example of the complementarity of radio astronomy and X-ray astronomy. This kind of approach is likely to be applied to observations of other black holes in the future.

A 50-Year Theoretical Prediction

When a black hole swallows surrounding gas, not all matter falls into the event horizon. Theoretically, some matter is ejected from the accretion disk as a hot plasma flow or jet. This “outflow” has been thought to play an important role in the black hole’s mass growth and the supply of energy to the surrounding environment.

However, Sgr A* at the center of our galaxy is a relatively quiet black hole, and bright jets like those in active galactic nuclei had not been observed. Therefore, the existence of an outflow had long remained a hypothesis. This discovery shows that even a mild black hole continuously releases gas, greatly advancing our understanding of the accretion and ejection mechanisms.

Technical Challenges and Their Value

Observing Sgr A* is technically extremely difficult. The galactic center is filled with interstellar dust and cannot be observed in visible light. Observations in radio and X-rays are essential, and detecting cold gas in the very vicinity of Sgr A* requires high spatial resolution and long-term integration observations. This study, which made full use of five years of ALMA data, once again highlights the importance of long-term observations.

The use of such long-term observation data is also valued in other fields of astronomy. For example, the value of insights obtainable only from long-term data was emphasized in the news of NASA’s Mars orbiter MAVEN concluding its decade-long observation mission. This is a good example of how utilizing data beyond the lifespan of an observation instrument can lead to new discoveries.

The method of using carbon monoxide molecules as a tracer is not new in itself, but applying it to the gas distribution in the immediate vicinity of Sgr A* and ensuring statistical significance is the innovation of this result.

Impact on Other Black Hole Research

This method can also be applied to other black holes in our galaxy and active galactic nuclei in nearby galaxies. Particularly, as ALMA’s performance improves and plans for next-generation telescopes progress, direct observations of outflows from more black holes will likely become possible.

Moreover, the cone-shaped cavity structure revealed by these observations is important for understanding how black holes affect the surrounding interstellar matter and star formation. The hot gas flow pushing aside cold molecular gas may suppress star formation in that region, or conversely, compress the gas and promote star formation.

These processes are essential elements in considering the evolution of entire galaxies and the co-evolution of black holes and galaxies. This direct observation will provide observational constraints for many theoretical models.

Persistence of 20,000 Years and Its Meaning

The research team estimates that this gas flow has persisted for at least about 20,000 years. This suggests that Sgr A*‘s accretion activity has been relatively stable over a long period. Black hole accretion can intermittently become intense, but this result indicates the existence of a mechanism that maintains a mild outflow stably.

A timescale of 20,000 years is not long astronomically, but it is far longer than human civilization. This shows that black hole activity can involve both short-term fluctuations and long-term stability on cosmic timescales.

Editorial View

Short-term Impact

This result has a major impact on the astronomical observation community. In particular, the effectiveness of the multi-wavelength collaboration between ALMA and Chandra has been demonstrated, making it highly likely that follow-up observations targeting other black holes will be proposed within the next six months. Furthermore, the use of CO molecules as a tracer will likely become common for objects other than Sgr A*. This is a typical case where advances in observation technology overtake theoretical predictions, and it is expected to influence the formulation of future research plans.

Long-term Perspective

Over a 1-3 year span, the application of this method to black holes outside our galaxy is anticipated to accumulate new insights into the relationship between outflows from active galactic nuclei and star formation. Additionally, if upgrades to ALMA and collaboration with next-generation interferometers (such as ngVLA) proceed, similar observations will become possible for even more distant black holes. This field is likely to become increasingly important as a bridge between observational and theoretical astronomy.

Questions from the Editorial Department

With the direct observation of a black hole’s “breathing,” we have gained a deeper understanding of the material cycle in the universe. However, questions remain. When did this gas flow start, and how will it change in the future? And to what extent does it contribute to the evolution of the entire galaxy? Answering these questions will require further long-term observations and refinement of theoretical models. Do our readers think this discovery will be a key to unraveling the mysteries of galaxy evolution?

References

• NRAO Press Release (Primary Source) — Published 2026-06-06
• Solidot Article (Original Article) — Published 2026-06-06