PHOTOS: Black Holes Blow More Cosmic Wind Into Galaxies Than First Thought

Hubble Space Telescope view of the spiral galaxy M83, which contains the powerful microquasar MQ1. Image courtesy of The Hubble Heritage Project

Black holes are gusty places, releasing more energy into their host galaxies than thought, say US and Australian scientists.

This finding will help us understand how black holes evolve and affect their host galaxies.

Gas in space flows, or accretes, onto black holes. That’s how they grow.

The gas inside gets so hot it emits radiation. According to the so-called Eddington limit, however, the radiation flowing outward cannot exceed a certain limit (one based on the black hole’s mass) or it will blow the in-flowing gas away.

Whether a black hole’s energy in the form of jets and winds is constrained by the same limit has been unclear.

Roberto Soria of the Curtin Institute of Radio Astronomy in Western Australia and colleagues in the US studied the outflow of a black hole far from the centre of its host galaxy, M83, for over a year.

Artist’s impression of a microquasar. Gas falls from a donor star towards the black hole. It spreads to form a hot accretion disk as it spirals down towards the hole, releasing gravitational energy; part of the energy is radiated as photons, part is used to launch a pair of jets. The characteristic scale of this cartoon picture is about 10 light seconds. The jets then travel for 10s or even 100s of light years, before slowing down and transferring their energy to the surrounding interstellar gas. Image courtesy of T.D. Russell (ICRAR-Curtin), using the BINSIM visualization code by R. Hynes (LSU)

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By analysing the gas accreting onto the black hole, they worked out its weight: less than 100 times that of the Sun.

The researchers compared this mass of the black hole with its outgoing power, a quantity they approximated from observations of the infrared and radio brightness of its surroundings.

The power flowing out was higher than the Eddington limit for a black hole of this mass, the researchers found.

This find suggests that black holes can give off very high kinetic, or mechanical, power for a long time, putting more energy into their environment than would be expected based only on their radiative power, which is subject to the Eddington limit.

The article, “Super-Eddington Mechanical Power of an Accreting Black Hole in M83”, is published in Science magazine, a journal of the American Association for the Advancement of Science.

Hubble Space Telescope view of the microquasar MQ1 in M83, observed with the Wide Field Camera 3 (combined Hydrogen and Sulfur emission). Two lobes of hot gas, created by the pair of jets, are clearly visible on either side of the central source.
Image courtesy of W.P. Blair (JHU) & R. Soria (ICRAR-Curtin)

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