Scientists have just discovered a distant galaxy with not one but three supermassive black holes at its core.
The new finding suggests that tight-knit groups of these giant black holes are far more common than previously thought, and it potentially reveals a new way to easily detect them, researchers say. Supermassive black holes millions to billions of times the mass of the sun are thought to lurk at the hearts of virtually every large galaxy in the universe.
Most galaxies have just one supermassive black hole at their center. However, galaxies evolve through merging, and merged galaxies can sometimes possess multiple supermassive black holes. [See amazing photos of galaxy mergers]
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Astronomers observed a galaxy with the alphabet soup name of SDSS J150243.09+111557.3, which they suspected might have a pair of supermassive black holes. It lies about 4.2 billion light-years away from Earth, said Roger Deane, a radio astronomer at the University of Cape Town in South Africa.
To investigate this galaxy, the scientists combined the signals from large radio antennas separated by up to 6,200 miles (10,000 kilometers). The technique helped researchers see details 50 times finer than is possible with the Hubble Space Telescope.
The astronomers discovered that the galaxy was not home to two supermassive black holes, but three. "All three of the black holes have masses around 100 million times that of the sun," Deane told Space.com.
Scientists had previously known of four triple black-hole systems. However, the closest pairs of black holes in those triplets are about 7,825 light-years apart. In this newfound trio of supermassive black holes, the closest pair of black holes is only about 455 light-years apart.
Closely orbiting black holes are expected to generate ripples in the fabric of space and time known as gravitational waves, which are theoretically detectable even from across the universe.
The scientists detailed their findings in this week's issue of the journal Nature.