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A Supermassive Black Hole Pairing

How do you get two supermassive black holes in each other’s neighborhood? That’s the question raised by the discovery of a pair of such objects, each 150 million times more massive than the Sun, and separated by a cosmically minute 24 light years. They’re in the center of a galaxy called 0402+379, some 750 million light years from Earth, and they orbit each other every 150,000 years.

“Astronomers have thought for a long time that close pairs of black holes should result from galaxy collisions,” says Cristina Rodriguez (University of New Mexico and Simon Bolivar University in Venezuela). And that’s apparently what happened here. Astronomers working with the Very Long Baseline Array (VLBA) radio telescope think that these black holes were each at the core of separate galaxies.

A collision between the galaxies would then have left the two objects orbiting each other. It would be intriguing indeed if the black holes themselves would collide, as the event should cause strong gravitational waves that could be detected with next-generation equipment like the Laser Interferometer Space Antenna (LISA). But a collision doesn’t seem to be in the cards for over a billion billion years.

Remarkably, collisions between galaxies are not uncommon, and the binary black hole pairs that result seem to become heavily involved in the subsequent evolution of these galaxies. Nor are pairs of smaller black holes a rarity; such pairings, each with a mass a few times that of the Sun, have been found in the Milky Way. But until now the closest confirmed pair of the supermassive variety were separated by 4500 light years. It took the continent-wide VLBA, which consists of ten radio-telescope antennae, to provide the resolving power to see two objects in such proximity.

Diagram of LISA mission

Image: LISA will be the first space-based mission to attempt the detection of gravitational waves. These are ripples in spacetime that are emitted by exotic objects such as black holes.

Centauri Dreams note: The LISA mission referenced above will consist of three spacecraft flying roughly 5 million kilometers apart, acting as an interferometer that can measure the distortions in space associated with gravitational waves. The waves should change the distance between the spacecraft in a direction that is perpendicular to the direction of the wave propagation. The distances involved are incredibly minute, but should be measurable by lasers aboard the spacecraft. Such observations should enable us to put General Relativity and black hole theory to the most accurate tests ever made.

Comments on this entry are closed.

  • Jyril May 2, 2006, 13:35

    I wonder if they have heard of the quasar [url=http://astronomy.swin.edu.au/sao/SAO_Observers/OJ287.html]OJ 287[/url], which is believed to have a binary black hole in its center. The black holes orbit each other causing major outbursts in the quasar. Orbital period of 11-12 years means they’re *way* closer each other than the black holes in 0402+379.

  • Administrator May 2, 2006, 13:56

    Good question! I don’t know anything about the quasar you mention, but my impression is that these are the first two _supermassive_ black holes in this configuration. I think that’s the difference. UPDATE: Having checked the reference, I think you’re right. The SAO Observers page says this: “The BL Lac object OJ 287 is the only known extragalactic source showing convincing evidence of a major periodical component in its optical emission. A popular model suggests it has a binary supermassive blackhole in its nucleus.” Which is fascinating stuff, and I’d love to get a comment from the VLBA team about it. Let me see if I can track down somebody to talk to there.

  • Administrator May 2, 2006, 19:08

    OK, here’s the answer straight from VLBA, though I’m not sure just who wrote it because it comes through their media contact: “Yes, the difference is that we have a direct detection as opposed to an inference based on a model. There are other likely explanations for the variability seen in OJ287. We also know quite a bit about our system (masses, orbital periods, environment, etc.) as compared to the indirect systems.”

  • ljk November 5, 2007, 11:34

    LISA sources and science

    Authors: Scott A. Hughes

    (Submitted on 1 Nov 2007)

    Abstract: LISA is a planned space-based gravitational-wave (GW) detector that would be sensitive to waves from low-frequency sources, in the band of roughly (0.03 – 0.1) mHz less than f less than 0.1 Hz. This is expected to be an extremely rich chunk of the GW spectrum — observing these waves will provide a unique view of dynamical processes in astrophysics.

    Here we give a quick survey of some key LISA sources and what GWs can uniquely teach us about these sources. Particularly noteworthy science which is highlighted here is the potential for LISA to track the moderate to high redshift evolution of black hole masses and spins through the measurement of GWs generated from massive black hole binaries (which in turn form by the merger of galaxies and protogalaxies). Measurement of these binary black hole waves has the potential to determine the masses and spins of the constituent black holes with percent-level accuracy or better, providing a unique high-precision probe of an aspect of early structure growth.

    This article is based on the “Astrophysics and Relativity using LISA” talk given by the author at the Seventh Edoardo Amaldi Conference on Gravitational Waves; it is largely an updating of the author’s writeup of a talk given at the Sixth International LISA Symposium.

    Comments: 8 pages, 2 figures. For the Proceedings of the 7th Edoardo Amaldi Conference on Gravitational Waves (to be published by Classical and Quantum Gravity)

    Subjects: General Relativity and Quantum Cosmology (gr-qc); Astrophysics (astro-ph)

    Cite as: arXiv:0711.0188v1 [gr-qc]

    Submission history

    From: Scott A. Hughes [view email]

    [v1] Thu, 1 Nov 2007 19:02:54 GMT (234kb)


  • Alex Clarke February 9, 2009, 0:03

    i wondered if black holes have any considered rotation of their own which may be apparent in the direction of rotation of the galaxy itself, (i asume during formation).in which case if black holes were to become close enough, and have oposite rotation or gravitational field this might cause a collapse or irregullarity in orbit of the galaxy.or posibly a separation of two halves.someone please let me know if i’am even in the ball park here.cheers