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Star Cluster Ejected From Galaxy At 2,000,000 MPH 133

William Robinson writes: "According to a new report, a globular cluster of several thousand stars (compressed into a space just a few dozen light-years apart) is being thrown out of galaxy M87. The cluster, named HVGC-1, is traveling at a rate of 2 million miles per hour. The discovery was made by Nelson Caldwell of the Harvard-Smithsonian Center for Astrophysics and his team while studying the space around the supergiant elliptical galaxy M87. Caldwell and colleagues think M87 might have two supermassive black holes at its center. The star cluster wandered too close to the pair, which picked off many of the cluster's outer stars while the inner core remained intact. The black holes then acted like a slingshot, flinging the cluster away at a tremendous speed."
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Star Cluster Ejected From Galaxy At 2,000,000 MPH

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  • Velocity (Score:5, Interesting)

    by dtmos ( 447842 ) * on Friday May 02, 2014 @09:34AM (#46898509)

    Two million miles per hour is less than 0.003c, but still quite a clip, even in astronomical terms.

    Since they're discussing velocity (vector speed), and not just speed, the headline is correct in saying " -1000 km/s" when the measured value is -1025 km/s, but one can debate whether the abstract is correct in saying "an extraordinary blueshift of -1025 km/s", rather than "an extraordinary blueshift of 1025 km/s", since "blueshift" gives one the sign of the velocity already.

  • Re:Velocity (Score:3, Interesting)

    by KrackerJax ( 83403 ) on Friday May 02, 2014 @09:37AM (#46898531)

    It would take a ship travelling at that speed roughly two days to travel from Earth to the Sun (1 AU). In those terms it doesn't seem all that fast. Pedestrian, really.

  • by tekrat ( 242117 ) on Friday May 02, 2014 @09:42AM (#46898567) Homepage Journal

    A cluster of stars were "thrown out" of galaxy M87?... what, they didn't pay the rent? Or is M87 expressing a case of "tough love"?

    The real question is; by what force were they ejected from the galaxy? The fastest we've ever been about to propel something is 24,000 mph -- and that's with a lot of gravity assists.... if we could figure out how to get a spacecraft to 2 million mph, trips around our solar system would go a lot faster.....

  • by wonkey_monkey ( 2592601 ) on Friday May 02, 2014 @10:00AM (#46898723) Homepage

    You say it "appears to be travelling in the opposite direction," but does it? It never gets any closer or any further away. Both ships are travelling around a common center, but relative to each other, are they in fact (as far as time dilation is concerned) stationary?

    So if both spaceships perceive that the other's clock is moving more slowly, what will they perceive if the spaceships come together to compare clocks?

    You can simplify (or in the light my above thought, perhaps even "make valid") this particular question a bit by considering the twin paradox instead. The same thing happens - the twin who stays at home considers the travelling twin's clock to be slower, but so does the traveller. And it's the same on the home trip, too, even though the traveller is now moving towards the stay-at-home. What breaks the symettry of the situation is that only one of them undergoes acceleration at the start, turnaround, and end points.

    If the traveller had stayed at Alpha Centauri and his lazy twin had ventured out to follow him at the same speed, their clocks would match.

    I suspect that the same applies to the circling ships - the clocks will match if neither breaks symmetry, otherwise they won't. And if the symmetry break is done only at non-relativistic speeds - i.e., both twins slow to a stop, then one tootles over to the other at 10km/h - the clocks will practically match.

  • Re:Velocity (Score:5, Interesting)

    by pr0t0 ( 216378 ) on Friday May 02, 2014 @10:13AM (#46898841)

    I wonder if the Earth was in orbit around a star that was part of such a cluster, would we notice the effects of such an ejection? Certainly the night sky would change, but the whole process could take of millions of years. Would we feel any immediate effects from the proximity to the black holes? What would our current state of technology, instrumentation and measurement tell us about our relative place and speed? And what, if any change would there be in our civilization's future. Not being in the galaxy seems isolating, but if the host star remains unchanged perhaps there is no change in our destiny. Or perhaps that by the time we developed interstellar travel we'd be too far from the host galaxy to travel to anything other than the stars in our cluster.

    It'd make for a good sci-fi book I think.

  • Another Question (Score:4, Interesting)

    by Mapleperson ( 1316213 ) on Friday May 02, 2014 @10:26AM (#46898947)
    Another questions is what happens to the speeding cluster if is was flung out by a bigger galaxy. One would assume the the dark matter that originally present in the cluster would not take the same track. Without the supporting dark matter the radial velocities are too great for the outer stars of the cluster to continue orbiting the system. One would think that there should be trail of stars left behind. Could be a great way to investigate dark matter interaction with galaxies.
  • by Thagg ( 9904 ) <thadbeier@gmail.com> on Friday May 02, 2014 @10:38AM (#46899051) Journal

    For a three-body slingshot to work, the object would have to get pretty close to one or both of the black holes -- considerably closer than the size of a globular cluster. At that distance, the tidal forces around the black holes would rip the cluster apart. I just can't see this happening.

    I suppose it's time to do some simulations :)

  • Re:Velocity (Score:2, Interesting)

    by siddesu ( 698447 ) on Friday May 02, 2014 @12:23PM (#46900213)

    would we notice the effects of such an ejection?

    Effects will depend on the differences of acceleration of different parts of the cluster. Because the speed has probably increased over many millenia, and because it is still a cluster, they were most likely very hard to observe.

  • Re:Velocity (Score:5, Interesting)

    by skastrik ( 971221 ) on Friday May 02, 2014 @12:26PM (#46900243) Journal
    Frederik Pohl's The World at the End of Time [wikipedia.org] deals with the ejections of solar systems on a grand scale.

Nothing succeeds like the appearance of success. -- Christopher Lascl