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The Black Hole Fountain: Matter is Blown Away ✛ ✦

Original: "General Relativistic Shock Wave Solutions with Black Hole Formation: The Singular Isothermal Sphere Case"
· Chien-Ting J. Chen, Michael J. Cai, Fabio Pacucci
arXiv:2606.29607 · 2026-06-28 · CC BY 4.0 · 1 min
High Energy Cosmology Galaxies General Relativity
Shock waves, like a splash from a narrow bottleneck, prevent a black hole from growing too fast.

The telescope James Webb has found black holes in the early Universe with masses of billions of suns, even though there was catastrophically little time for them to grow. One explanation is the direct collapse of a huge cloud almost devoid of heavy elements. But such an infall is anything but calm.

During the rapid compression, a shock wave arises — like water splashing out of a narrow neck if you pour it too fast.

This 'fountain' accelerates gas to half the speed of light and flings it away. Only later, when the funnel of curved spacetime catches up with the matter, does it fall into the central point of zero size.

As a result, the black hole receives 5–7 times less mass.

But the same wave, according to the mass-energy equivalence law, converts up to a tenth of the infalling gas into radiation — twice as efficiently as the spinning gas disk. This flare heats the cloud, creating bright 'cocoons' that Webb sees in the active nuclei of distant galaxies (their light is strongly reddened due to the Universe's expansion).

Without the fountain, the black hole would grow quietly and remain invisible — nature prefers a fireworks display.

The calculations are based on the Schwarzschild solution for black holes, the general relativity equations of Einstein, and the theory of shock discontinuities of Landau; disruptions in the flow are inevitable according to the law of increasing disorder, and future computer simulations will test these ideas.

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For a black hole to shine at the edge of the Universe, it first has to spit out almost everything it planned to devour.

p_{\rm pre} p_{\rm post} = \frac{\gamma}{1+\gamma}
The product of the proper momenta of the gas before and after the shock front is constant and depends only on the square of the sound speed.
Scientists
Stephen HawkingJacob BekensteinAlbert EinsteinBarry BarishKip ThorneRichard Feynman
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supermassive black hole growth schwarzschild black hole schwarzschild metric critical collapse innermost stable circular orbit mass inflation hawking radiation mechanism nuclear reaction mass gap hawking area law quasistar wave amplification radio loud quasar ringdown kerr metric gravitational wave echoes scalar perturbations logarithmic correction gravitational singularity Penrose singularity theorem Birkhoff's theorem