Energy Efficient Black Holes

Recent findings show that old black holes still have some kick to them, able to turn matter into energy with an efficiency that would equate to a billion miles on a single tank of gas.

The study of nine supermassive black holes, ranging in age from 50 million to 400 million years old, showed that they converted approximately 2.5% of the rest-mass energy of collected matter into streaming jets of high-energy x-ray particles moving at up to 95% the speed of light. The power of these jets come out to "about a trillion, trillion, trillion watts," according to researchers. In comparison, quasars (the most efficient mass-energy converters known) converts approximately 5% of incoming mass into energy.

Christopher Reynolds of the University of Maryland said the older black holes "attracted our attention because they were too boring." Previous models had supposed that older black holes lost their efficiency at a much greater rate, sucking in surrounding gas and providing little output, so this finding will cause revisions to our understanding of the life cycles of black holes. At present, only speculations exist as to exactly what mechanism allows for the efficient conversion of mass to energy.

The energy of these x-ray jets heats surrounding interstellar gas to the point where it cannot condensce into new stars, which may also explain why the galaxies with these old black holes have few young stars.

The findings are being reported in an upcoming issue of Monthly Notices of the Royal Astronomical Society and more details can be found in the journal Science and Scientific American magazine.

The image to the right is a NASA artistic rendering of a black hole.