Dual Black Holes Spinning in a Cosmic Dance – Complete with Disco Ball

Article written: 4 Jan , 2010
Updated: 26 Apr , 2016

Caption: An image of the galaxy COSMOS J100043.15+020637.2 taken with the Advanced Camera for Surveys on the Hubble Space Telescope. Image courtesy Dr. Julia Comerford.

Astronomers have discovered 33 pairs of merging black holes in cosmic dances around each other, a finding that was predicted or ‘choreographed’ by Isaac Newton. “These results are significant because we now know that these ‘waltzing’ black holes are much more common than previously known,” said Dr. Julia Comerford of the University of California, Berkeley, at the American Astronomical Society meeting in Washington, DC. “Galaxy mergers are causing the waltzing, can use this finding to determine how often mergers occur. The black holes dancing towards us are shifted towards blue light, and those moving away from us are shifted toward the red. So it is like a cosmic disco ball showing us where the black holes are dancing.”

The dances are occurring in dual black holes, which are different from binary black holes in that the distance between the two object is much larger for dual black holes.

“These black holes have a separation of a kilo parsec,” said Comerford. “You haven’t heard about lots of small binary black holes, because no one has definitively found any yet. But this is the next best thing. We know these duals are going to merge and can use models to find out how often they merge.”

The team was able to observe the black holes that have gas collapsing onto them, and this gas releases energy and powers each black hole as an active galactic nucleus (AGN), which lights up the black hole like a Christmas tree.

Astronomical observations have shown that nearly every galaxy has a central supermassive black hole (with a mass of a million to a billion times the mass of the Sun), and also that galaxies commonly collide and merge to form new, more massive galaxies. As a consequence of these two observations, a merger between two galaxies should bring two supermassive black holes to the new, more massive galaxy formed from the merger. The two black holes gradually in-spiral toward the center of this galaxy, engaging in a gravitational tug-of-war with the surrounding stars. The result is a black hole dance. Such a dance is expected to occur in our own Milky Way Galaxy in about 3 billion years, when it collides with the Andromeda Galaxy.

The team of astronomers used two new techniques to discover the waltzing black holes. First, they identified waltzing black holes and their velocities by the disco ball of the red-shift or blue-shift.

The second technique for identifying waltzing black holes through a chance discovery of a curious-looking galaxy. While visually inspecting images of galaxies taken with the Advanced Camera for Surveys on the Hubble Space Telescope, the team noticed a galaxy with a tidal tail of stars, gas, and dust, an unmistakable sign that the galaxy had recently merged with another galaxy, and the galaxy also featured two bright nuclei near its center. The team recognized that the two bright nuclei might be the AGNs of two waltzing black holes, a hypothesis seemingly supported by the recent galaxy merger activity evinced by the tidal tail. To test this hypothesis, the very next night the team obtained a spectrum of the galaxy with the DEIMOS spectrograph on the 10-meter (400-inch) Keck II Telescope on Mauna Kea, Hawaii.

The spectrum showed that the two central nuclei in the galaxy were indeed both AGNs, supporting the team’s hypothesis that the galaxy has two supermassive black holes. The black holes may be waltzing within the host galaxy, or the galaxy may have a recoiling black hole kicked out of the galaxy by gravity wave emission; additional observations are necessary to distinguish between these explanations.

Comerford said these new techniques can be used to find many more waltzing pairs in the future.

Source: AAS, Dr. Julia Comerford’s website

10 Responses

  1. Mr.No.Scope says

    The black holes dancing towards us are red-shifted with blue light, and those moving away from us are shifted toward the red. Red-shifted with blue light? I do believe this means that they are blue-shifted, not red-shifted.

    This is analogous to saying you are driving forward in reverse.

  2. Member
    Jon says

    So is this how spiral arms are formed in galaxies? Seems like if you have two massive black holes combining in a galaxy merger and they circle each other in such a manner, spiral arms could easily be the result of such a vortex and it’s tidal forces on gravity and time.

  3. Lawrence B. Crowell says

    It will be a long time before the BHs coalesce. When they do about 28% of the mass of the black holes will be converted to gravitational waves. That is a lot of energy, but it couples very weakly with matter, and the effect out to our distance will be small. It will not happen for many millions of years, so don’t expect a LIGO signal from this.


  4. Andy Gordon says

    I figured these were fairly common when I found examples during my Galaxy Zoo explorations. I’m surprised to read that astronomers have found only 33.

    Here’s a link to the pair I found in a galactic merger:

  5. Torbjorn Larsson OM says

    @ Jon:

    I’m no astronomer, but I have gotten the impression from last year’s press that galaxies starts out as small spirals concomitant with a central massive black hole. Incessant galactic mergers seems to result in “ellipticity”, explaining first the bulge and perhaps also the halo of clusters, finally wholesale ellipticals.

    If that is true, mergers destroy spiral arms, not creates them.

  6. Torbjorn Larsson OM says

    Um, also, “tidal forces” “on time”: a short distance away from the black hole you wouldn’t note any gravitational difference between a BH and the ordinary mass that went into creating it. In general, weak gravity doesn’t affect time beyond the emergence of spacetime itself.

    Besides I don’t think it makes sense to speak of “tidal effects” on space and time, as tidal effects happen in spacetime.

    [This is interestingly a tie-in to QM. Seems QM and GR together explains why spacetime is hyperbolic. Maintaining GR CTC “time travel spacetimes” implies using infinite energies classically in their neighborhood, so the correspondence principle implies there’s no renormalizable QM solutions in their neighborhood. Away goes time traveling and similar non-hyperbolic properties.

    Seems we need GR and QM together to have spacetime emerge in the weak gravity regime. Likewise have them together to destroy spacetime in black holes or similar strong gravity regime conditions. GR and QM are twins even outside of string theory.]

  7. Lawrence B. Crowell says

    In the weakest domain of gravity general relativity reduces to Newtonian gravity. It is not hard to see how weak the Earth’s gravity is. A bit of static electricity can hold a mass against gravity. Another case is the surface tension of a liquid. The following video


    is interesting to watch, where the coalescence of water drops on a water surface induces a van derVall induced surface wave that can pop a small drop upwards against gravity.

    Quantum gravity really obtains at pretty high energy, with some suggestions of weak or small quantum gravity signatures that might occur at the LHC domain of energy in the TeV range. Quantum gravity though occurs for very small regions or high energy, such as near black hole singularities or for the intense gravity around quantum black holes smaller than the nucleus of an atom.


  8. secondguess says

    I had read a student’s masters thesis, which he had based almost completly on BHs moving vast distances. Some moving in very strange directions, such as in the opposite directions as the expanding universe theory. I, for one have never bought into ‘moving BHs’ so I thought and realized, BHs would be moving along with the expanding universe. But how could they be moving ‘against the flow’. Maybe a ‘sling shot’ effect with a larger or more dense BH?

  9. secondguess says

    Then I thought could there be a heavier more dense matter which could cause something as substantial as a BH to behave so oddly?

    just a thought

  10. Jon Hanford says

    A short paper describing the discovery of this object can be found here: http://arxiv.org/PS_cache/arxiv/pdf/0906/0906.3517v1.pdf .

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