Are Rogue Black Holes Wandering the Universe?

Article written: 4 Jun , 2012
Updated: 23 Dec , 2015


Talk about a tough neighborhood! Even black holes aren’t welcome in galaxy CID-42, located about 4 billion light-years away from Earth. Astronomers using the Chandra X-Ray Observatory have found strong evidence that a massive black hole is being ejected from this galaxy, moving out at a speed of several million kilometers per hour. This phenomenon, known as a recoiled black hole, happens due to a gravitational wave “kick” from the merger of two black holes.

While this event is likely to be rare, it could mean that there could be giant black holes roaming undetected out in the vast spaces between galaxies.

“These black holes would be invisible to us,” said Laura Blecha from the Harvard Center for Astrophysics, co-author of a new study, “because they have consumed all of the gas surrounding them after being thrown out of their home galaxy.”

Previous looks at CID-42 detected a bright X-ray source likely caused by super-heated material around one or more supermassive black holes. However, astronomers could not distinguish whether the X-rays came from one or both of the optical sources because Chandra was not pointed directly at CID-42, giving an X-ray source that was less sharp than usual.

The new data help to clarify that X-rays were coming only from one of the sources. The team thinks that when two galaxies collided, the supermassive black holes in the center of each galaxy also collided. The two black holes then merged to form a single black hole that recoiled from gravitational waves produced by the collision, which gave the newly merged black hole a sufficiently large kick for it to eventually escape from the galaxy.

“It’s hard to believe that a supermassive black hole weighing millions of times the mass of the Sun could be moved at all, let alone kicked out of a galaxy at enormous speed,” said Francesca Civano of the Harvard-Smithsonian Center for Astrophysics (CfA), who led the new study. “But these new data support the idea that gravitational waves — ripples in the fabric of space first predicted by Albert Einstein but never detected directly — can exert an extremely powerful force.”

Almost a century ago, Albert Einstein formulated the modern set of equations — general relativity — that are used to describe gravity.

“Einstein’s equations are so complicated that we were able to solve them accurately only a few years ago for a relatively simple system of two black holes in a bound orbit,” said co-author Avi Loeb from the Harvard Center for Astrophysics. “Such a system forms naturally as a result of a merger between two galaxies, each hosting a single black hole at its center. The exact solution to Einstein’s equations, obtained with sophisticated computer algorithms, shows that the two black holes merge into a single black hole which is kicked in a preferred direction like a rocket due to the directional emission of gravitational waves which serve as the substance coming out from the rocket exhaust.”

If CID-42 was indeed produced by this mechanism, it provides the first observational validation of Einstein’s equations in the unexplored regime of dynamical strong gravity, which is responsible for gravitational wave kicks.

Additional data from the ground-based Magellan and Very Large Telescopes in Chile supplied a spectrum that suggested the two sources in CID-42 are moving apart at a speed of at least 5 million kilometers per hour (3 million miles per hour).

There are two other possible explanations for what is happening in CID-42. One would involve an encounter between three supermassive black holes, resulting in the lightest one being ejected. Another idea is that CID-42 contains two supermassive black holes spiraling toward one another, rather than one moving quickly away.

Both of these alternate explanations would require at least one of the supermassive black holes to be very obscured, since only one bright X-ray source is observed. Thus the Chandra data support the idea of a black hole recoiling because of gravitational waves.

These results will appear in the June 10 issue of The Astrophysical Journal.

Read the team’s papers:
Chandra High resolution Observations of CID-42, a candidate recoiling SMBH
Constraints on the Nature of CID-42: Recoil Kick or Supermassive Black Hole Pair?

Source: NASA, Chandra


10 Responses

  1. Chris Devriese says

    “two sources in CID-42 are moving apart at a speed of at least 1 million kilometers per second” … ? don’t thing so…

    • lcrowell says

      It is a 1 million kilometers per hour.


      • IVAN3MAN_AT_LARGE says

        Actually, it’s 5 million kilometers per hour – the original article states 3 million miles per hour.   I e-mailed a note to Nancy last night about that.

  2. Chris Devriese says

    “two sources in CID-42 are moving apart at a speed of at least 1 million kilometers per second” … ? don’t thing so…

  3. Member
    Aqua4U says

    What stands out para moi is: “…kicked in a preferred direction like a rocket due to the directional emission of gravitational waves which serve as the substance coming out from the rocket exhaust.”

    Sci Fi anyone? An advanced civilization roams our galaxy, exploring time and space. The ships they use travel vast distances with unimaginably powerful engines which enable them to approach the speed of light. Due to the tremendous forces generated gravitational waves disturb local time/space continuum(s) creating local condensates which gravitationally adhere and compress and which eventually create strings of stars in their wake.

    In travels through our galaxy they have left many trails. Have you seen them?

    • Torbjörn Larsson says

      Simple counter-argument: these “unimaginably powerful engines” would have to be comparable to super-massive black holes, in which case they would be – (super-massive) black holes. “Unimaginable” seems a good characterization. =D

  4. lcrowell says

    The process is something I have been trying to look up. It is similar to a particle scattering of two particles into a vertex or “blob” which then decays into two other particles. In this case it amounts to

    BH + BH — > BH + GW

    BH = black hole and GW = gravitational wave. This is an interesting and complicated problem. I am gophering around to find sources, such as

    The process might be compared to the situation where an electric charge is adjusted with some electromagnetic field response. If you have a single charge that is adjusted, say moved some vector direction x there is a dipole moment P = ex. A current j is a time rate of change of the charge and is related to the vector potential A = ?d^3x j/|x – x’|. So we can construct the electromagnetic vector potential. The dipole transition does not work for gravitational radiation. The dipole moment P = ex varies with time as dP/dt = edx/dt. The dipole moment analogue for mass is P = mx and the time rate of change is momentum. Dipole transitions for masses require a change in momentum in the whole system, which is not permitted. So the transition must involve quadrupole moments.

    Kepler’s laws of planetary motion are a form of quadrupole moment dynamics. A dipole transition will occur for a circular orbit of a charge around an opposite charge. Elliptical orbits are a case of quadrupole moments. The eccentricity of the orbit is a measure of the qudrupole moment. The Somerfeld generalization of the Bohr model of the hydrogen atom has elliptical orbits of the electron and thus qudrupole moments. Two stars in a mutual orbit with a nonzero eccentricity can emit gravitational radiation. The evolution in the pulsar timing of two neutron stars in orbit found by Hulst and Taylor is an indirect measurement of gravitational radiation.

    The gravitational radiation produced by the coalescence of black holes is a canonical result. If we have two equal mass, M, black holes the Schwarzschild radius is r = 2GM/c^2. The area of the event horizons are A = 4?r^2. The coalescence of the two black holes result in a black hole with radius R such that

    4?R^2 >= 2(4?r^2) = 8?r^2

    or R >= sqrt{2}r. The mass of the resulting black hole is M’ = sqrt{2}M. Yet the total mass involved is 2M, so the amount of mass not found in the resulting black hole is 2M – sqrt{2}M = (2 – sqrt{2})M = .586M. This means a lower bound of 29% of the mass-energy of the two initial black holes is converted to gravitational radiation. That is enormous amount of energy! However, the coupling constant for these waves with matter is 8?G/c^4 which is very small. So the physical effect at much of a distance is quite small.

    The details of the gravitational radiation emitted are however far more difficult to compute. Most people who do these calculations use numerical methods. The equations are very nonlinear, and further this process is the transition of type D solutions to type D + type N solutions. This is a type of problem in general relativity which has no general system of solutions.


  5. bugzzz says

    oh great, a kajillion rogue planets floating throughout the universe and now black holes too!

  6. dovhenis says

    Ejected black holes, or holes that completed gulping of their surroundings?

    Natural Selection Is Ubiquitous

    Higgs Particle? Dark Energy/Matter? Epigenetics?
    These Are YOK!
    Update Concepts-Comprehension…

    Evolution Is The Quantum Mechanics Of Natural Selection.
    The quantum mechanics of every process is its evolution.
    Quantum mechanics are mechanisms, possible or probable or actual mechanisms of natural selection.

    Universe-Energy-Mass-Life Compilation

    A. The Universe

    From the Big-Bang it is a rationally commonsensical conjecture that the gravitons, the smallest base primal particles of the universe, must be both mass and energy, i.e. inert mass yet in motion even at the briefest fraction of a second of the pre Big Bang singularity. This is rationally commonsensical since otherwise the Big would not have Banged, the superposition of mass and energy would not have been resolved.

    The universe originates, derives and evolves from this energy-mass dualism which is possible and probable due to the small size of the gravitons.

    Since gravitation Is the propensity of energy reconversion to mass and energy is mass in motion, gravity is the force exerted between mass formats.

    All the matter of the universe is a progeny of the gravitons evolutions, of the natural selection of mass, of some of the mass formats attaining temporary augmented energy constraint in their successive generations, with energy drained from other mass formats, to temporarily postpone, survive, the reversion of their own constitutional mass to the pool of cosmic energy fueling the galactic clusters expansion set in motion by the Big Bang.

    B. Earth Life

    Earth Life is just another mass format. A self-replicating mass format. Self-replication is its mode of evolution, natural selection. Its smallest base primal units are the RNAs genes.

    The genesis of RNAs genes, life’s primal organisms, is rationally commonsensical thus highly probable, the “naturally-selected” RNA nucleotides.

    Life began/evolved on Earth with the natural selection of inanimate RNA, then of some RNA nucleotides, then arriving at the ultimate mode of natural selection, self-replication.

    C. Know Thyself. Life Is Simpler Than We Are Told, Including Origin And Nature Of Brain And Of “Spirituality”***

    The origin-reason and the purpose-fate of life are mechanistic, ethically and practically valueless. Life is the cheapest commodity on Earth.

    As Life is just another mass format, due to the oneness of the universe it is commonsensical that natural selection is ubiquitous for ALL mass formats and that life, self-replication, is its extension. And it is commonsensical, too, that evolutions, broken symmetry scenarios, are ubiquitous in all processes in all disciplines and that these evolutions are the “quantum mechanics” of the processes.

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    Human life is just one of many nature’s routes for the natural survival of RNAs, the base Earth organism.

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    Dov Henis (comments from 22nd century)

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