Keck: Two black holes may have collided

Scientists using Mauna Kea’s W.M. Keck Observatory have peered 90 million light years from Earth into a region located within the Big Dipper and made a surprising discovery.


Scientists using Mauna Kea’s W.M. Keck Observatory have peered 90 million light years from Earth into a region located within the Big Dipper and made a surprising discovery.

If their findings are proven right by further analysis, a team of astronomers believes it has captured evidence of two black holes merging. Like a pair of billiard balls of unequal size spinning in opposite directions and then colliding, the smaller of the two black holes may have been kicked away, flying out of its home galaxy, known as Markarian 177, and dragging with it a cloud of glowing, superheated gas and material that can be directly measured using various instruments, said Roy Gal, an astronomer with the University of Hawaii Institute for Astronomy.

The very existence of black holes — which contain so much mass that their gravitational pull becomes strong enough to pull anything toward them, including light — has only recently been proven through observation, making further discoveries like this one an exciting proposition, Gal said.

“There has been one other candidate for an object like this, but this is the best and most convincing one found so far,” he said.

All told, there is only a handful of black holes that have ever been conclusively identified, and this would be the first example of the celestial bodies merging and creating a rogue black hole shooting off through intergalactic space. The team will be able to confirm its findings in October 2015, when they are scheduled to use the Cosmic Origins Spectrograph aboard the Hubble Space Telescope.

“They’ll be getting the spectrum of the light and more details of the composition and energetics of the object, providing a diagnostic of what it is,” Gal said.

While the scientists believe they have found evidence of a so-called “recoiling black hole” following a collision, there is another possibility that will either be confirmed or discounted based on the Hubble findings. Their evidence could also point to the object, known as SDSS1133, being the remnant of a massive star that underwent a record period of eruptions before destroying itself in a supernova explosion. Such a star, which is relatively rare, is known as a Luminous Blue Variable.

If the object turns out to be an LBV, it would represent the longest period of eruptions ever observed in an object of its type. The light from its destruction — known as a terminal supernova — would have reached the Earth in 2001, with the light waves now being collected representing its final death throes.

“With the data we have in hand, we can’t yet distinguish between these two scenarios,” said Michael Koss, an astronomer at ETH Zurich, the Swiss Federal Institute of Technology. “One exciting discovery made with NASA’s Swift is that the brightness of SDSS1133 hasn’t changed in ultraviolet light for a decade, which is not something typically seen in a young supernova remnant.”

Led by Koss, who was a postdoctoral fellow at the IfA at the University of Hawaii at Manoa during the majority of the time the study was ongoing, the team published its findings in the Nov. 21 edition of Monthly Notices of the Royal Astronomical Society.

The study involved data collected by a number of telescopes, including Hawaii Island’s Keck, NASA’s Swift telescope, which operates from low-Earth orbit, and the Pan-STARRS1 telescope atop Haleakala on Maui.

Keck’s contribution to the study came in June 2013, when researchers obtained high-resolution, near-infrared images of SDSS1133 using the observatory’s 10-meter Keck II telescope.

“When we analyzed the Keck data, we found the emitting region of SDSS1133 is less than 40 light-years across, and that the center of Markarian 177 shows evidence of intense star formation and other features indicating a recent disturbance that matched what we expected for a recoiling black hole,” said Chao-Ling Hung, a UH-Manoa graduate student performing the analysis of the Keck imaging in the study.


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