For the first time, scientists have proof two
\nsupermassive black holes exist together in the same galaxy,
\nthanks to data from NASA’s Chandra X-ray Observatory.
\n
\nThese black holes are orbiting each other and will
\nmerge several hundred million years from now, to
\ncreate an even larger black hole resulting in a
\ncatastrophic event that will unleash intense
\nradiation and gravitational waves.<\/p>\n
\nThe Chandra image reveals that the nucleus of an
\nextraordinarily bright galaxy, known as NGC 6240, contains
\nnot one, but two giant black holes, actively accreting
\nmaterial from their surroundings. This discovery shows that
\nmassive black holes can grow through mergers in the centers
\nof galaxies, and that these enigmatic events will be
\ndetectable with future space-borne gravitational wave
\nobservatories.<\/p>\n
\n“The breakthrough came with Chandra’s ability to clearly
\ndistinguish the two nuclei, and measure the details of the X-
\nradiation from each nucleus,” said Guenther Hasinger, of the
\nMax Planck Institute for Extraterrestrial Physics in Germany,
\na coauthor of an upcoming Astrophysical Journal Letters paper
\ndescribing the research. “These cosmic fingerprints revealed
\nfeatures characteristic of supermassive black holes — an
\nexcess of high-energy photons from gas swirling around a
\nblack hole, and X-rays from fluorescing iron atoms in gas
\nnear black holes,” he said.<\/p>\n
\nPrevious X-ray observatories had shown that the central
\nregion produces X-rays, while radio, infrared and optical
\nobservations had detected two bright nuclei, but the nature
\nof this region remained a mystery. Astronomers did not know
\nthe location of the X-ray source, or the nature of the two
\nbright nuclei.<\/p>\n
\n“With Chandra, we hoped to determine which one, if either, of
\nthe nuclei was an active supermassive black hole,” said
\nStefanie Komossa, also of the Max Planck Institute, lead
\nauthor of the paper on NGC 6240. “Much to our surprise, we
\nfound that both were active black holes!”<\/p>\n
\nAt a distance of about 400 million light-years, NGC 6240 is a
\nprime example of a massive galaxy in which stars are forming
\nat an exceptionally rapid rate due to a recent collision and
\nsubsequent merger of two smaller galaxies. Because of the
\nlarge amount of dust and gas in such galaxies, it is
\ndifficult to peer deep into their central regions with
\noptical telescopes. However, X-rays emanating from the
\ngalactic core can penetrate the veil of gas and dust.<\/p>\n
\n“The detection of a binary black hole supports the idea that
\nblack holes can grow to enormous masses in the centers of
\ngalaxies by merging with other black holes,” said Komossa.
\n“This is important for understanding how galaxies form and
\nevolve,” she said.<\/p>\n
\nOver the course of the next few hundred million years, the
\ntwo black holes in NGC 6240, which are about 3000 light-years
\napart, will drift toward one another and merge to form an
\neven larger supermassive black hole. Toward the end of this
\nprocess an enormous burst of gravitational waves will be
\nproduced several hundred million years from now.<\/p>\n
\nThese gravitational waves will spread through the universe
\nand produce ripples in the fabric of space, which would
\nappear as minute changes in the distance between any two
\npoints. NASA’s planned space-based detector, LISA (Laser
\nInterferometer Space Antenna), will search for gravitational
\nwaves from massive black-hole mergers. These events are
\nestimated to occur several times each year in the observable
\nuniverse.<\/p>\n
\n“This is the first time we see a binary black hole in action,
\nthe smoking gun for something that will become a major
\ngravitational wave burst in the future,” said Hasinger.<\/p>\n
\nChandra observed NGC 6240 for 10.3 hours with the Advanced
\nCCD Imaging Spectrometer (ACIS). Other members of the team
\nare Vadim Burwitz and Peter Predehl of the Max Planck
\nInstitute, Jelle Kaastra of the Space Research Organization
\nNetherlands and Yasushi Ikebe of the University of Maryland
\nin Baltimore.<\/p>\n
\nNASA’s Marshall Space Flight Center in Huntsville, Ala.,
\nmanages the Chandra program for the Office of Space Science,
\nWashington, and TRW, Inc., Redondo Beach, Calif., is the
\nprime contractor for the spacecraft. The Smithsonian’s
\nChandra X-ray Center controls science and flight operations
\nfrom Cambridge, Mass.<\/p>\n
\nImages and additional information about this result are
\navailable at:
\n
\nhttp:\/\/chandra.harvard.edu <\/a><\/p>\n