Spinning black holes are ultimate cosmic batteries - 26 January 2009 by *David Shiga*<http://www.newscientist.com/search?rbauthors=David+Shiga> - Magazine issue 2692 <http://www.newscientist.com/issue/2692>. * Subscribe* <http://www.newscientist.com/subscribe?promcode=nsarttop> and get 4 free issues.
YOU wouldn't want to be nearby when a spinning black hole<http://www.newscientist.com/article/dn10611-spinning-black-hole-is-fastest-on-record.html>[image: Movie Camera] lets rip. It now seems they can store and unleash the energy of billions of supernovae, with potentially devastating consequences for their host galaxies. Many of the supermassive black holes that lurk at the centre of galaxies fire out powerful plasma jets that extend for millions of light years. Though the details of how these jets are produced remain murky, there seems to be only two plausible power sources: one is matter falling onto the black hole, which can't explain all the cases. The other source is the black hole's stored rotational energy<http://www.newscientist.com/article/dn6278-spinning-black-holes-fire-off-violent-jets.html>. Calculations suggest it should be possible for jets to siphon off energy at the expense of the black hole's rotation as long as magnetic fields are present to connect the black hole to any matter nearby. Persuasive evidence for this has been lacking. Now a team led by Brian McNamara of the University of Waterloo, Canada, has found what may be the strongest evidence yet for jets powered by black hole rotation. It comes from a galaxy called MS0735.6+7421 (pictured), about 2.6 billion light years from Earth. In 2005 data on this galaxy from the Chandra X-ray Observatory revealed the biggest outpouring of energy ever identified from black hole jets. Based on cavities the jets have apparently punched through the surrounding gas, the team calculates that in the past 100 million years or so jets have put out 1055 joules, billions of times the energy of a supernova. It would have been next to impossible for matter falling into the black hole to power these jets. Supermassive black holes are messy eaters, leaving behind many times more matter than they actually consume but there is little sign that this happened. "It would have had to essentially vacuum all of the matter that was in that galaxy down into the black hole in a period of 100 million years, and we know nature doesn't work that way," McNamara says. "Accretion of matter onto a black hole is very inefficient" (www.arxiv.org/abs/0811.3020). That leaves black hole spin as the only other energy source. The black hole could have been set spinning in the first place by matter falling onto it much earlier in its lifetime or in the course of a merger with another black hole. A huge amount of energy can be stored in black hole spin, and if it gets released again in the form of jets, it could have profound effects. Black hole jets are increasingly suspected of sterilising their host galaxies<http://www.newscientist.com/article/dn8405-black-holes-colossal-sphere-of-influence-revealed.html>, heating and blowing away gas before it can condense to form new stars, for example. Chris Reynolds of the University of Maryland in College Park says this strengthens the case that some jets are powered by spinning black holes. But he says he is still waiting for "definitive proof". http://www.newscientist.com/article/mg20126924.700-spinning-black-holes-are-ultimate-cosmic-batteries.html --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Cosmology, Mathematics and Philosophy" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to cosmology-mathematics-and-philosophy+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/cosmology-mathematics-and-philosophy?hl=en -~----------~----~----~----~------~----~------~--~---
