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New Class of "Hypervelocity Stars" Discovered Escaping the Galaxy 150

Posted by samzenpus
from the greased-lightning dept.
Science_afficionado writes "Astronomers have discovered a surprising new class of 'hypervelocity stars' that are moving at more than a million miles per hour, fast enough to escape the gravitational grasp of the Milky Way galaxy. The 20 hyper stars are about the same size as the sun and, other than their extreme speed, have the same composition as the stars in the galactic disk. The big surprise is that they don't seem to come from the galaxy's center. The generally accepted mechanism for producing hypervelocity stars relies on the extreme gravitational field of the supermassive black hole that resides in the galaxy's core."
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New Class of "Hypervelocity Stars" Discovered Escaping the Galaxy

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  • by Anonymous Coward

    Maybe they're motherships :D

    • by Cryacin (657549) on Thursday January 09, 2014 @09:27PM (#45913075)
      Maybe those starts just didn't like the neighbourhood they were in and decided to move house.
      • Maybe those starts just didn't like the neighbourhood they were in and decided to move house

        TFA only says that the stars are travelling at a speed high enough that they can escape the pull of the galaxy, but doesn't give any explanation of WHAT is pushing or pulling the stars.

        From TFA:

        "The generally accepted mechanism for producing hypervelocity stars relies on the extreme gravitational field of the supermassive black hole that resides in the galaxy's core"

        If it's the "supermassive black hole in the Galaxy core" that's doing the pulling, the stars should have travelling towards the core.

        But they are travelling instead away from the core !

        Instead of a "pull", it is as if there's something that's "PUSHING" them instead, and I do not think it's the supermassive blackhol

        • by znanue (2782675) on Friday January 10, 2014 @03:29AM (#45914535)

          Due to inertia, the stars would continue to travel at their current speeds if nothing were pushing and pulling on them. As it is, whatever gravitational forces are acting upon them at the moment might be comparatively insignificant to their current inertia.

          So how did they get their current inertia? They might have gotten it from the supermassive black hole at the galaxy's core without setting their vector towards the core. They could do so possibly using a gravity slingshot effect [discovery.com]. So it is surprising they're not coming from the core, as the article states. So what is interesting about these stars is they don't seem to be explained by the slingshot effect.

          Further, gravity is a force of attraction and so does no pushing.

          Also, I did a knapkin calculation of the speeds involved and it would be 1/700th the speed of light except the article says that this speed is relative to the movement of the galaxy and not an absolute speed like the slashdot summary intimates.

          • by Anonymous Coward on Friday January 10, 2014 @05:24AM (#45914837)

            There is no such thing as "absolute speed"; all movement is relative to other objects in the universe.

        • by Maritz (1829006)

          They travel towards it on a trajectory that takes them close to, but not lethally close to, the black hole. They gain so much velocity that they continue out never to return again. If ISON (the comet) had not burned up, the sun would have done the same thing to it.

          It's the same general idea as the gravity assist maneuvers that are usually required to send probes to the outer solar system in a reasonable time frame.

          • by RockDoctor (15477)

            They travel towards it on a trajectory that takes them close to, but not lethally close to, the black hole. They gain so much velocity that they continue out never to return again.

            Close, but no cigar.

            You need three bodies to interact : a massive central body ("primary") and two "light" (relatively small, but not zero mass) "secondary" objects. All three orbit around their mutual barycentre ("centre of gravity", but it moves as the positions of the three objects change in relation to each other) and the two

    • by icebike (68054) on Thursday January 09, 2014 @09:50PM (#45913251)

      A million miles per hour is not all that much.

      All the galaxies in our neighborhood are also rushing at a speed of nearly 1,000 kilometers per second (2,236.936 miles per hour) towards a structure called the Great Attractor, a region of space roughly 150 million light-years away.

      In addition, our solar system--Earth and all--whirls around the center of our galaxy at some 220 kilometers per second, or 490,000 miles per hour.

      The earth is moving toward the Constellation Leo at the dizzying speed of 390 kilometers per second. (872,405 miles per hour).

      Lots stuff going places fast.

      Now if you find an inhabitable planet orbiting one of these stars let me know. That would be the mothership of all motherships.

      • "1,000 kilometers per second (2,236.936 miles per hour)"

        Either kilometers are a lot shorter than I remember, or you got your periods and commas mixed up somewhere.

        • by icebike (68054)

          Should have been all commas. Doh.
          At least for those of us on this side of the pond.

          • by RockDoctor (15477)

            Should have been all commas. Doh.
            At least for those of us on this side of the pond.

            Well, for some of you on whichever side of whichever Pond you're on.

      • by Charliemopps (1157495) on Thursday January 09, 2014 @10:12PM (#45913409)

        Now if you find an inhabitable planet orbiting one of these stars let me know. That would be the mothership of all motherships.

        Or really bad luck. Leaving the galactic plane would pretty much assure your species would never branch out beyond your own solar system.

        • by icebike (68054)

          Maybe they already did that.

          Like the GP suggested: Motherships.
          What better space ship can you conceive of than traveling with an entire solar system?
          Who knows how many worlds they might have seeded.

          Some seem to be passing by our neighborhood. Mom? Where are you going?

          • yea, but they are headed in the wrong direction, and are moving REALLY slow. If we saw stars moving around at a few percent the speed of light, then maybe. But a million miles per hour? That's 0.0014% the speed of light. Our closest neighbor is 25.8 trillion miles away. So it would take them nearly 3 thousand years just to get there. Not much of a mother ship.

            • by cusco (717999)

              Who says that 70 years is the maximum average lifespan for sentient beings? We may be abnormally short-lived, and 3000 years might not be an unreasonable time for an explorer to spend on an epic voyage. Yeah, not really applicable here, but it's an objection that I always hear as to why interstellar flight is impossible.

              • by cellocgw (617879)

                We may be abnormally short-lived, and 3000 years might not be an unreasonable time for an explorer to spend on an epic voyage

                Yep, just ask the Dwellers. (Iain Banks)

              • My point is, if they have the power to move a star, they sure as hell have a faster/better way to get where they're going without the star.

                • Why not carry around with you a significant power source, that will last potentially billions of years? Sure there could be better or faster ways, but I'd think the star itself would be a precious asset while going out of galaxy!

              • by RockDoctor (15477)

                the maximum average lifespan

                You need a "statistics grammar" filter before posting. I can work out what you probably mean, but what you've typed is incoherent.

            • by Wycliffe (116160)

              yea, but they are headed in the wrong direction, and are moving REALLY slow. If we saw stars moving around at a few percent the speed of light, then maybe. But a million miles per hour? That's 0.0014% the speed of light. Our closest neighbor is 25.8 trillion miles away. So it would take them nearly 3 thousand years just to get there. Not much of a mother ship.

              3000 years wouldn't be much of a journey if you are taking your planet with you. For instance if we knew our sun was going
              to die in 5000 years and we wanted to relocate our planet to a new sun and we didn't want to be cramped in small spaceships
              or abandon our home then moving our solar system to a new solar system and then "swapping suns" would seem like a reasonable
              option assuming we had the capability of doing it. It also eliminates the need of having to find a suitable planet to teraform.

          • by Maritz (1829006)
            A few interesting thoughts on that idea here [centauri-dreams.org]. Put a lampshade on your star basically.
        • Or really bad luck. Leaving the galactic plane would pretty much assure your species would never branch out beyond your own solar system.

          But the view of the Milky Way would be gorgeous!

      • by camperdave (969942) on Thursday January 09, 2014 @11:09PM (#45913693) Journal
        Everybody sing!

        Just remember that you're standing on a planet that's evolving
        And revolving at nine hundred miles an hour,
        That's orbiting at nineteen miles a second, so it's reckoned,
        A sun that is the source of all our power.
        The sun and you and me and all the stars that we can see
        Are moving at a million miles a day
        In an outer spiral arm, at forty thousand miles an hour,
        Of the galaxy we call the 'Milky Way'.
        Our galaxy itself contains a hundred billion stars.
        It's a hundred thousand light years side to side.
        It bulges in the middle, sixteen thousand light years thick,
        But out by us, it's just three thousand light years wide.
        We're thirty thousand light years from galactic central point.
        We go 'round every two hundred million years,
        And our galaxy is only one of millions of billions
        In this amazing and expanding universe.

        The universe itself keeps on expanding and expanding
        In all of the directions it can whizz
        As fast as it can go, at the speed of light, you know,
        Twelve million miles a minute, and that's the fastest speed there is.
        So remember, when you're feeling very small and insecure,
        How amazingly unlikely is your birth,
        And pray that there's intelligent life somewhere up in space,
        'Cause there's bugger all down here on Earth.
        • Re: (Score:2, Informative)

          by Anonymous Coward

          Those are cool lyrics.. did you write that yourself?
          Don't be an Apple...

            - Galaxy Song Lyrics by Monty Python

        • Catchy tune - we used to square dance to it :-)

      • by Maow (620678) on Friday January 10, 2014 @02:45AM (#45914417) Journal

        A million miles per hour is not all that much.

        All the galaxies in our neighborhood are also rushing at a speed of nearly 1,000 kilometers per second (2,236.936 miles per hour) towards a structure called the Great Attractor, a region of space roughly 150 million light-years away.

        I think they're calling them fast based on the relative speed to the galaxy that they're being ejected from / passing though.

        Astrophysicists calculate that a star must get a million-plus mile-per-hour kick relative to the motion of the galaxy to reach escape velocity.

        The diagram in TFA seems to indicate that these stars are not originating inside the galaxy, which to me raises the question, from whence do they come?

        This image [vanderbilt.edu] makes it appear the stars are mostly passing through the disk of the galaxy. I may be reading too much into the length of the coloured lines though.

        • by Vitriol+Angst (458300) on Friday January 10, 2014 @10:16AM (#45915943)

          They are likely wandering stars from another galaxy. Wasn't it estimated that we already had one galaxy pass through the Milky Way and sometime in the future we may pass through Andromeda?

          So perhaps there are three mechanisms for high speed stars;
          1) ejected by a super massive black hole.
          2) remnant of non-colliding stars from Galactic collisions (and actually, most stars don't hit each other in these situations).
          3) L3 advanced civilization finding that solar tourism is more fun if you can take all your stuff with you.

      • by Katatsumuri (1137173) on Friday January 10, 2014 @05:00AM (#45914787)

        One of the theories for the origin of these hypervelocity stars is 3-body chaotic gravity assist. When two bodies are entering a gravity assist trajectory around a third, very massive body, their interactions sometimes add up in such a way that one body falls into a tight orbit, and another is ejected at a hypervelocity. Given the number of ternary star systems in the galaxy, this looks like a plausible explanation.

        There is even a paper suggesting we could build an interstellar starship from two asteroids [prescientmodels.com] (PDF, 10 pages) using this mechanism. It was written by Josef L Breeden and presented at the 100 Year Starship conference.

      • by RockDoctor (15477)

        A million miles per hour is not all that much.

        For a sun-like star, that's around a diameter per hour.

        Hardly speedy.

    • by meerling (1487879) on Thursday January 09, 2014 @09:51PM (#45913263)
      It's not the Puppeteer Homefleet, they aren't flying in formation.

      (If you don't know what I'm talking about, look up author Larry Niven.)
      • It was reminding me of the Fast Protosun. Of course, there's a big gap between 10^6 mph and 0.8c. Not to mention a number of other likely differences (not least because they would be spoilers).

  • Heavens Gate was right all along! We missed the Mothership, guys!
  • by Anonymous Coward on Thursday January 09, 2014 @09:30PM (#45913085)

    This is obviously 'Wan-to' up to his old tricks again.

  • by Anonymous Coward

    They've spotted the explosion! Get in your General Products Hull and run for it! Our only salvation will be to find the Ringworld and move it out of the galaxy!

  • Assuming ... (Score:5, Interesting)

    by TrollstonButterbeans (2914995) on Thursday January 09, 2014 @09:37PM (#45913141)
    Assuming the observation gets studied and confirmed, this is probably far more common than one might initially expect.

    The Milky Way has been on the move billions of years and occasionally meets up with star clusters or even dwarf galaxies.

    Many of them probably settle in gravitationally, but some of them aren't going to and continue, largely, about their merry way if the relative speeds are right.

    These stars could have been "acquired" 400 million years ago and it can take a long time to traverse a cross-segment of the Milky Way. And these stars would have to be smaller like our sun to have the right lifespan, and we wouldn't notice the really small ones (red dwarfs and such) because they would be hard to see so there is also a mix of observational factors in the equation.
    • Beat me to the hypothesis. Just because a star is in the milky way doesn't mean that it was formed there. It may just be passing by, with its doors locked and hoping to look inconspicuous because it's got a similar composition as the local hot hooligans (how likely is that? that's not specified in TFS)

    • by TMB (70166)

      Except that if the star was captured by the Milky Way, that already tells you that it was moving at less than the escape velocity, while these are moving faster than the escape velocity.

      Still, it would be interesting to see if they share orbital elements with known satellites or streams...

      [TMB]

    • by Anonymous Coward

      TFA says that those stars appear to have the same composition as normal disk stars, so they cannot come from dwarf galaxies.

      Also, traversing the disk at 'hypervelocity' takes definitely less than 400 million years. Mind that our Sun takes just half that go around the disk at about half its diameter and at a regular velocity.

    • TFA says these were calculations done on the Sloan Digital Sky Survey data, which was released to the world in 2008 according to their homepage, so the actual observations are already "confirmed" in that sense. I'm assuming the current study released their calculations and methods so anyone can double check them.
  • Maybe two super-massive black holes passed close to each other and spun these off?
    • by tftp (111690)

      Maybe two super-massive black holes passed close to each other and spun these off?

      Perhaps. But now instead of explaining why one common star is moving somewhere fast you need to explain why two uncommon black holes are moving somewhere fast, and on top of that why they nearly hit each other and some common star...

  • by Rick in China (2934527) on Thursday January 09, 2014 @09:51PM (#45913259)
    Looking at the trajectories, wouldn't it be a possibility that these stars didn't originate in our galaxy, but rather, could have been tourists flung out in a similar fashion from another supermassive black hole outside of our own galaxy? Just passing through on various trajectories, from potentially various other galaxies. Not much thought put into this - maybe the distance from the nearest supermassive black hole outside of our own galaxy makes this an impossibility, but seems the article doesn't go into any theories at all.
    • by jheath314 (916607)

      It's possible, I suppose. The Andromeda galaxy is the closest large neighbor to the Milky Way, and it is 2.5 million light years away. At "more than a million miles per hour" (0.0015 c) a star would take only one or two billion years to make the trip across the intergalactic void... a long journey, to be sure, but doable within a stellar lifetime. However, because our galaxy occupies less than 1% of the sky as seen from Andromeda, the odds of randomly flung stars hitting our galaxy from that distance awa

  • They're just trying to see what they can get away with with a Newtonian approximation of gravity [io9.com].
  • by BringsApples (3418089) on Thursday January 09, 2014 @09:57PM (#45913311)
    Aren't all objects' movement (speed) based on another objects movement (speed)? I mean, how fast is the Milky Way moving, and in what direction? And could that star just be sitting idle-ish, and our galaxy zipping past it? Are these question answerable?
    • by Uecker (1842596) on Thursday January 09, 2014 @10:17PM (#45913437)

      If one considers the rest frame of the microwave background as the rest frame of the universe, then yes, one can answer these questions.

      http://en.wikipedia.org/wiki/Cosmic_microwave_background [wikipedia.org]

    • by Shavano (2541114)

      You're missing the point. These are stars moving at at abnormal speeds and can't be explained by any phenomenon we have observed before.

    • by KliX (164895) on Friday January 10, 2014 @01:24AM (#45914239)

      'Relative' is the key. There is no fixed background to say 'This is going absolutely this fast', any observation point in any kind of motion is as viable as any other. It just falls out of a little bit of simple vector maths - so no, your question is not answerable, as it's malformed.

      • I'm sure there have been some tests, but has anyone conclusively found a "vector" to space? Currently, we use Universal Background Radiation -- allegedly this is the noise left over from the poorly named "Big Bang".

        The problem of Relativity is that either their is a universal time or all time is local -- and each object has a relative time displacement to each other. In the simple model of relativity, you have an observer, or someone leaves a planet at high speed and comes back and their clocks have account

        • There is no universal time or space frame of reference; there are merely frames of reference that are convenient to use. For some purposes, using the CMB is quite handy.

          In the rocket experiment, the difference in experienced time beween rocket and Earth has nothing to do with any absolute reference frame, but rather that the rocket changes reference frames and Earth doesn't. This is experienced as acceleration. For purposes of Special Relativity, if you feel no acceleration you're staying in the same

      • by volmtech (769154)
        Maybe I have misinterpreted the question. The speed of light is absolute. We can measure exactly how fast we are in motion in this universe. At least that is what I was taught in high school fifty years ago.
    • by idji (984038) on Friday January 10, 2014 @03:38AM (#45914563)
      This speed is still very fast if it is taken relative to us or to the galactic center. The galaxy's speed relative to the cluster plays no role at these sizes and time scales. "sitting idle-ish and the galaxy zipping past" is the classic Relativity - it makes no difference - both are identical. In either case something caused that Star's velocity relative to us to by very different.
    • by Kjella (173770)

      I think it theory you can use the fact that c is constant to prove your absolute speed. Imagine you send a single photon down both ends of a tube and measure where they meet. You know both photons have travelled at the same speed and so covered the same distance. Imagine your ship travels at 0.5c and the tube is 100cm, in the time it takes the photons to cover 50cm each your ship will have moved 25cm so they actually meet at 75/25cm not 50/50cm as you'd expect. Get a perfect 50/50cm in three axis and you wi

      • You're actually fairly close to the Michelson-Morley experiment there, although they were measuring speeds at right angles. The answer is that, given no acceleration, the photons will meet in the middle no matter how the ship moves relative to anything. The failure of Michelson and Morley to find any difference in observed speeds was considered very odd at the time, and led to relativity.

        The speed of light in vacuum is the same under all conditions. Once you accept this, and ditch concepts like "at th

  • I guess (Score:3, Funny)

    by Anonymous Coward on Thursday January 09, 2014 @10:33PM (#45913531)
    the radio waves with Fox News started reaching them.
  • those aren't stars escaping the galaxy... those are golf balls being hit by people that watched those 8 free HD golf lesson videos to learn that weird golf trick to add an extra 20 yards.
  • Ah -- all those sorry imperia that are reminded of when their deficient units of measurement find
    their only shelter in planetary travel and galactic theories.
    Is the galaxy Anglosaxon? No, all rejoice -- it is not.

  • Puppeteer planets escaping.

  • by symbolset (646467) * on Thursday January 09, 2014 @11:45PM (#45913845) Journal
    From the ratio of stars being ejected, get the average rate of galaxy evaporation. Calculate backward to compute original mass of the milky way.
  • by 93 Escort Wagon (326346) on Friday January 10, 2014 @12:04AM (#45913909)

    These stars were ejected by the polar vortex.

  • I'd think an N-body problem with 300 billion stars would almost inevitably produce a few stars that just by chance get a sufficient number of gravitational slingshots from other stars that they get up to escape velocity...

  • Those are spaceships!
  • by locopuyo (1433631) on Friday January 10, 2014 @02:46AM (#45914419) Homepage
    Somebody stop them!
  • What would happen if one of these beasts passed near the Solar system. For "near" consider the following scenarios: 1. Oort cloud. 2. Kuiper belt (I don't recall which one is closer and I'm too lazy to google it). 3. Just outside the orbit of Neptune. 4. Collision with Jupiter. 5. A passage inside the orbit of Mercury, no planetary collision or collision with Sol.

    Finally, assuming none of these scenarios killed us by disruption the relationship between the Earth and Sun or flinging large bodies a

  • His take [centauri-dreams.org] on such matters is generally well informed and interesting.

  • I wonder how it would have felt for humanity if Earth happened to orbit such a star, and we knew that every moment we were going farther and farther from the galaxy.

  • I have read quite a bit about science that interests me and one of the subjects was "the ultimate fate of the universe". One detail that stuck out was that all galaxies evaporate given enough time. Even with a small rate of evaporation (say, an average of 10 billion years for any given star), our galaxy has 300 billion stars, so you're bound to see a few flying away "naturally" at any point time.

    If they really wanted to know how these particular stars got boosted without going through the galactic center,

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