Why do some stars in the galactic center survive while others are destroyed?

The center of our galaxy is an extreme place. Surrounding the supermassive black hole Sagittarius A*, stars are packed densely into a region where gravity, radiation, and dark matter all interact in complex ways. It is a natural laboratory for testing some of the deepest ideas about astrophysics.

Yet this region presents a puzzle.

Compact stars—such as neutron stars and white dwarfs—are expected to accumulate dark matter over time, especially in such dense environments. Under the right conditions, this accumulation can trigger the formation of a tiny black hole at the very center of the star.

Once formed, the black hole should begin to grow by accreting the surrounding stellar material. The expected outcome is dramatic: The star is gradually consumed from within and eventually collapses entirely into a black hole.

If this picture were complete, many compact stars in the galactic center should already have been destroyed. But observations suggest otherwise.

Clues from surviving stars

Some stars clearly survive. Others appear to be missing. This uneven outcome raises a fundamental question: What determines whether a star lives or dies in such an environment?

One particularly intriguing clue comes from the magnetar PSR J1745-2900, located remarkably close to Sagittarius A*. Magnetars are neutron stars with extremely strong magnetic fields, and this object is both highly magnetized and stable. Its survival is not easy to reconcile with the expectation of rapid destruction driven by internal black hole growth.

At the same time, there is evidence for an overabundance of strongly magnetized white dwarfs near the galactic center.

In contrast, ordinary pulsars—neutron stars with comparatively weaker magnetic fields—appear to be underrepresented, a long-standing issue often referred to as the “missing pulsar problem.”

Taken together, these observations suggest that not all stars share the same fate. Something must be influencing the outcome.

Can magnetic fields change the outcome?

A natural candidate is magnetism.

Compact stars can host some of the strongest magnetic fields in the universe. In many astrophysical environments, magnetic fields are known to regulate how matter moves, especially in accretion processes. They can channel, redistribute, or even suppress the flow of matter onto compact objects. This raises an important possibility: Could magnetic fields also influence the growth of a black hole forming inside a star?

In recent work, this possibility was explored in detail. The findings are published in The European Physical Journal C.

The central idea is that if a small black hole forms at the core of a strongly magnetized star, it does not grow in isolation. Instead, it is embedded in a medium where magnetic forces are significant. These fields can exert pressure and tension that oppose the inward flow of matter toward the black hole.

As a result, the accretion process—the mechanism that drives black hole growth—can be substantially reduced.

Magnetically arrested transmutation

In this picture, the black hole may still form, but its growth is effectively slowed or even halted. Instead of a runaway process in which the star is inevitably consumed, the system becomes regulated. The star could survive for much longer timescales, potentially remaining observable.

This mechanism is referred to as magnetically arrested transmutation (MAT).

MAT provides a natural way to understand the contrasting observations in the galactic center. Stars with strong internal magnetic fields, such as magnetars or highly magnetized white dwarfs, may be protected from rapid destruction.

Their magnetic fields act as a barrier that limits the growth of any black hole forming inside them. On the other hand, stars with weaker magnetic fields may lack this protection, making them more vulnerable to being consumed from within.

In this way, magnetic fields may effectively decide the fate of compact stars in extreme environments.

Rethinking black hole growth

This perspective also offers a new way to think about black holes. They are often described as relentless consumers of matter, growing whenever material is available. However, the environment in which a black hole resides can play a crucial role. In strongly magnetized systems, growth is not guaranteed. Instead, it can be suppressed by the very conditions surrounding the black hole.

The implications extend beyond individual stars. If magnetic fields influence survival rates, they could shape the population of compact objects observed near the galactic center. The apparent scarcity of ordinary pulsars, the survival of magnetars like PSR J1745-2900, and the presence of magnetized white dwarfs may all be connected through this single underlying mechanism.

This story is part of Science X Dialog, where researchers can report findings from their published research articles. Visit this page for information about Science X Dialog and how to participate.

Chandrachur Chakraborty is a Theoretical Astrophysicist at the Manipal Center for Natural Sciences (MCNS), Manipal Academy of Higher Education, India, and an Associate at the Inter-University Center for Astronomy and Astrophysics, Pune, India. His research focuses on General Relativity with its applications to Astrophysics: sites.google.com/view/chandrachur

H. A. Adarsha is a Ph.D. student at MCNS.

Sudip Bhattacharyya is an observational Astrophysicist at the Tata Institute of Fundamental Research, Mumbai, India.