For something so dark it could define the word, black holes sure seem to be generating a lot of light at the 215th meeting of the American Astronomical Society in Washington, D.C. At a press conference yesterday morning, several scientists spoke about their recent research into these objects, whose gravity is so strong that not even light can escape them. Fortunately for astronomers, a black hole can radiate lots of energy when surrounding matter gets heated to millions of degrees.
Jimmy Irwin of the University of Alabama talked about his team’s
discovery of an intermediate black hole ripping a star apart. The black hole lies in a globular cluster belonging to the galaxy NGC 1399. Observations show the globular emits lots of X-rays — a telltale sign in these objects of a black hole accreting matter. Optical spectra show oxygen and nitrogen emission but no hydrogen, which implies the black hole is swallowing material from a white dwarf star. The material’s velocity implies the black hole has at least 1,000 times the Sun’s mass.
The other speakers discussed supermassive black holes in other galaxies. Julia Comerford of the University of California, Berkeley reported on her team’s
discovery of 33 dual black holes — those that form when two galaxies collide and bring along their supermassive black holes. Eventually the black holes merge, but before then they perform an intricate dance with each other. The 33 dual black holes suggest galaxy mergers are much more common than previously thought.
Ruth Daly of Penn State University discussed the spins of the black holes in 55 distant galaxies. The black holes ranged from hundreds of millions to billions of solar masses. She found that the spins range from 10 to 100 percent of the maximum possible, and that the more distant black holes rotated faster than nearby ones. This implies that the spin rates decrease as the black holes age.