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Three black holes found spiraling into each other

June 26, 2014
Courtesy of the University of Oxford
and World Science staff

As­tro­no­mers say they have de­tected three gi­ant black holes spi­ral­ing in­to each oth­er. They’re hop­ing si­m­i­lar sys­tems could give off de­tect­a­ble “rip­ples” in space and time of a type pre­dicted by Ein­stein.

Scientists ex­am­ined six sys­tems thought to con­tain two “su­per­mas­sive” black holes. A black hole is an ob­ject so com­pact that its gra­vity over­pow­ers even light. Su­per­mas­sive black holes are a mam­moth type, which lurk at the cen­ters of ga­lax­ies and an­chor them to­geth­er.

The re­search­ers found that one of these con­tained three su­per­mas­sive black holes – the tight­est tri­o of black holes de­tected at such a large dis­tance – with two of them or­bit­ing each oth­er rath­er like bi­na­ry, or dou­ble stars. The find­ing sug­gests that these closely packed su­per­mas­sive black holes are far more com­mon than pre­vi­ously thought, the sci­en­tists said. A re­port of the re­search is pub­lished in this week’s is­sue of the jour­nal Na­ture.

“What re­mains ex­tra­or­di­nary to me is that these black holes, which are at the very ex­treme of Ein­stein’s The­o­ry of Gen­er­al Rel­a­ti­vity, are or­bit­ing one anoth­er at 300 times the speed of sound on Earth,” said Rog­er Deane from the Uni­vers­ity of Cape Town in South Af­ri­ca, who led the proj­ect.

“Not only that, but us­ing the com­bined sig­nals from ra­di­o tele­scopes on four con­ti­nents we are able to ob­serve this ex­ot­ic sys­tem one third of the way across the Uni­verse,” he added. The dis­tance is es­ti­mat­ed as four bil­lion light-years. A light-year is the dis­tance light trav­els in a year.

“This is just scratch­ing the sur­face of a long list of dis­cov­er­ies that will be made pos­si­ble with the Square Kil­o­me­ter Ar­ray,” a new tel­e­scope sys­tem, he added.

The ex­pecta­t­ion is that such black holes would eventually merge, giv­ing off these waves pre­dicted by Ein­stein. “The idea that we might be able to find more of these po­ten­tial sources of gravita­t­ional waves is very en­cour­ag­ing as know­ing where such sig­nals should orig­i­nate will help us try to de­tect these ‘rip­ples’ in space-time as they warp the Uni­verse,” said as­t­ro­phys­i­cist Matt Jarvis of Ox­ford Uni­vers­ity, a co-author of the pa­per.

“We have man­aged to spot three black holes packed about as tightly to­geth­er as they could be be­fore spi­ral­ing in­to each oth­er and merg­ing.”

The team used a tech­nique called Very Long Base­line In­ter­fer­om­etry to dis­cov­er the in­ner two black holes. This tech­nique com­bines the sig­nals from large ra­di­o an­ten­nas sep­a­rat­ed by up to 10,000 kilo­me­ters (6,200 miles) to see de­tail 50 times fin­er than that pos­si­ble with the Hub­ble Space Tel­e­scope. Fu­ture ra­di­o tele­scopes are ex­pected to be able to meas­ure the gravita­t­ional waves from such black hole sys­tems as the ob­jects fall in­to each oth­er.

The re­search­ers al­so found that even though black holes may be so close to­geth­er that our tele­scopes can’t tell them apart, the twisted jets of par­t­i­cles that they give off may pro­vide easy-to-find point­ers to them, much like us­ing a flare to mark your loca­t­ion at sea. This could pro­vide sen­si­tive fu­ture tele­scopes a way to find such ob­jects more eas­i­ly.


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Astronomers say they have detected three giant black holes spiraling into each other. They’re hoping similar systems could give off detectable “ripples” in space and time of a type predicted by Einstein. Astronomers examined six systems thought to contain two “supermassive” black holes. A black hole is an object so compact that its gravity overpowers even light. “Supermassive” black holes are a mammoth type, which lurk at the centers of galaxies and anchor them together. The researchers found that one of these contained three supermassive black holes – the tightest trio of black holes detected at such a large distance – with two of them orbiting each other rather like binary, or double stars. The finding suggests that these closely packed supermassive black holes are far more common than previously thought, the scientists said. A report of the research is published in this week’s issue of the journal Nature. “What remains extraordinary to me is that these black holes, which are at the very extreme of Einstein’s Theory of General Relativity, are orbiting one another at 300 times the speed of sound on Earth,” said Roger Deane from the University of Cape Town in South Africa, who led the project. “Not only that, but using the combined signals from radio telescopes on four continents we are able to observe this exotic system one third of the way across the Universe,” he added. The distance is estimated as four billion light-years. A light-year is the distance light travels in a year. “This is just scratching the surface of a long list of discoveries that will be made possible with the Square Kilometer Array,” a new telescope system, he added. The expectation is that such black holes would eventually merge, giving off these waves predicted by Einstein. “The idea that we might be able to find more of these potential sources of gravitational waves is very encouraging as knowing where such signals should originate will help us try to detect these ‘ripples’ in space-time as they warp the Universe,” said astrophysicist Matt Jarvis of Oxford University, a co-author of the paper. “We have managed to spot three black holes packed about as tightly together as they could be before spiraling into each other and merging.” The team used a technique called Very Long Baseline Interferometry to discover the inner two black holes. This technique combines the signals from large radio antennas separated by up to 10,000 kilometers (6,200 miles) to see detail 50 times finer than that possible with the Hubble Space Telescope. Future radio telescopes are expected to be able to measure the gravitational waves from such black hole systems as the objects fall into each other. The researchers also found that even though black holes may be so close together that our telescopes can’t tell them apart, the twisted jets of particles that they give off may provide easy-to-find pointers to them, much like using a flare to mark your location at sea. This could provide sensitive future telescopes a way to find such objects more easily.