A long-held theory of why interstellar black holes show different effects when viewed from Earth may have to be reexamined in the light of latest data from a NASA space telescope, astrophysicists say.
Astronomers attempting to explain that emissions of some black holes as they gobble up surrounding matter are difficult to observe while others appear clear and visible developed the so-called "doughnut" theory, a unified model that held all black holes are encircled by a torus -- doughnut-shaped assemblies of gas and dust that would affect how a black hole appeared depending on its orientation.
If seen edge on from earth, such a doughnut would obscure a black hole and its energy output, while if seen from below or above it would allow a clear view of a black hole region.
So far so good, but latest survey by NASA's Wide-field Infrared Survey Explorer (WISE) space telescope of thousands of supermassive black holes puts that theory in doubt because it doesn't adequately explain what they see.
The problem arose in WISE observations of both exposed and hidden black holes in massive galaxies bunched together into clusters, which showed more of them obscured than the "doughnut" theory would suggest.
If the theory holds, obscured black holes and exposed black holes ought to cluster in the same manner and in equivalent numbers, the researcher said.
The theory may have to be reconsidered, because if galaxies that clump together show more hidden black holes, it suggests there's something beyond the unified torus model at work -- perhaps dark energy.
"The main purpose of unification was to put a zoo of different kinds of active [black hole] nuclei under a single umbrella," says lead researcher Emilio Donoso, of the Instituto de Ciencias Astronómicas, de la Tierra y del Espacio in Argentina.
"Now, that has become increasingly complex to do as we dig deeper into the WISE data," he says.
Dark matter -- invisible but making up the majority of all matter in the universe -- may be more concentrated around large galactic clusters, affecting whether black holes are exposed or not.
However, the mechanism of how that might work is unknown, astrophysicists say.
"The unified theory was proposed to explain the complexity of what astronomers were seeing," study co-author Daniel Stern of the Jet Propulsion Laboratory in Pasadena, California, says.
"It seems that simple model may have been too simple. As Einstein said, models should be made 'as simple as possible, but not simpler'."
