Scientists have long known that the supermassive black hole lurking in the belly of the Milky Way ingests very little matter, but previous estimates of a one percent consumption rate of fuel could be a significant overestimate.

The fuel for Sagittarius A* (or Sgr A* for short) is provided by local massive young stars but because these stars are located some distance from the hungry black hole where its gravity is significantly weaker, it struggles to capture and swallow the high-velocity stellar winds. Scientists had estimated that it feeds on about one percent of this stellar fuel, but a new model based on Chandra X-ray Observatory observations suggest it could be as little as one percent of that one percent.

The new model considers the flow of energy between an inner region near to the black hole's event horizon – the boundary beyond which even light cannot escape – and an outer region some million times further out that contains the young stars. Collisions between particles in the hot inner region transfer energy to particles in the cooler outer region, which in turn creates a pressure that makes most of the gas in the outer region flow away from the black hole.

The model appears to explain well the extended shape of hot gas detected around Sgr A* in X-rays as well as features seen in other wavelengths. Lobes of hot gas extending for 12 light years on either side of the black hole are seen in the new deep image taken by Chandra, and show evidence for powerful eruptions occurring several times over the last ten thousand years.

Mysterious X-ray filaments are also seen in the image, and may mark the locations where huge magnetic structures are interacting with streams of energetic electrons produced by rapidly spinning neutron stars – features known as pulsar wind nebulas.

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