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27-Feb-2014

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Black holes give off stronger winds than we thought



Composite image of the spiral galaxy M83 assembled from observations made by NASA's Hubble Space Telescope and the Carnegie Institution of Washington's Magellan telescopes.
[NASA, ESA, the Hubble Heritage Team (STScI/AURA)]

Black holes release more energy into the galaxies they live in than previously thought, a new study in the 28 February issue of the journal Science suggests.

This finding will help scientists better model changes in black holes over time, and it will also help them better understand how these mysterious regions affect their host galaxies. Gas in space can flow, or accrete, onto black holes; that's how black holes grow. The gas inside gets so hot it emits radiation.

According to a theory of physics called the Eddington limit, the radiation flowing outward cannot exceed a certain limit or it will blow the inflowing gas away.

Whether a black hole's kinetic energy (energy from wind) is controlled by the same limit has been unclear.

To shed some light on the matter, scientists lead by Roberto Soria of Australia's Curtin University studied the outflow of a black hole in galaxy M83. They observed it with telescopes for over a year.

By analyzing the gas accreting onto the black hole, they figured out the black hole's weight: less than 100 times that of the Sun (comparing objects to the weight of the Sun is common in astronomy).

The researchers compared the mass of the black hole with its outgoing kinetic power, which they were able to infer in part by looking at the light around it.

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

This finding 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 radiation energy, which is subject to the Eddington limits.

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