Why Are These Stars Fleeing The Milky Way?

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Astronomers have discovered a new class of potential hypervelocity stars that could suggest an alternative escape route from the galaxy.

Hypervelocity stars are so called because, uh, they travel really fast—enough to break free from the galaxy. Astronomers have long known that this can happen when a binary star system gets caught in a black hole’s grip. Under the right circumstances, one of the stars spirals in toward the black hole while the other is violently flung outward at a tremendous speed.

Over the past decade, astronomers have found 18 such speedy blue stars in the Milky Way that could have been created this way, all tracing their birthplace to the supermassive black hole at the Galactic center. But an international team of researchers has now discovered a new batch of 20 sun-sized hypervelocity stars that don’t appear to originate from the Galactic core, presenting a mystery to astronomers about their origins. The study was presented at the annual meeting of the American Astronomical Society last week.

 

Written By: Jia You
continue to source article at popsci.com

11 COMMENTS

      • In reply to #3 by john.wb:

        http://www.purdue.edu/impactearth

        The 11 km/sec they quote is nowhere near “hypervelocity”.

        In 2005 Smithsonian astronomers discovered the first “hypervelocity star:” – (http://www.cfa.harvard.edu/oir/sp/hypervel.html) a massive star whose 2 million mph velocity can be explained only by ejection from the Galaxy’s massive black hole. This “outcast” star has been thrown out of the Milky Way and is destined to drift in the emptiness of intergalactic space. Smithsonian astronomers are leading the discovery of new hypervelocity stars. Hypervelocity stars tell us about the types of stars orbiting near the central black hole, and the history of stellar interactions with the central black hole.

        they don’t list “star” as an option but if you choose “small planet” you can see we would be pretty much history :)

        A low velocity impact on Earth by a small planet has already been calculated and is probably history. Giant impact hypothesis

        A hypervelocity planet would smash us to smithereens or vapour. Fortunately the vast spaces between stars make this very unlikely.

        In reply to #1 by A3Kr0n:

        I wonder how big of a crater a hyper-velocity star would make if it hit us?

        An impact of a hypervelocity star on a large planet or the Sun would probably destroy the Solar System in its present form.

        @OP – But an international team of researchers has now discovered a new batch of 20 sun-sized hypervelocity stars that don’t appear to originate from the Galactic core,

        There are smaller black-holes orbiting within the Milkyway, so I guess they are a probable source.

    • In reply to #5 by Net:

      i’m grateful and interested in the message, but oh how i hate the writing.

      Hypervelocity stars are so called because, uh, they travel really fast

      Yeah, the very first sentence – in the caption – has bad grammar. One does appreciate that she’s taken the trouble to lay out this long description for the non-astronomers among us, but you’d think that after all that trouble, she’d have it edited. It diminishes the impact of the otherwise fascinating message when it’s poorly written.

      And before I am accused of being a grammar Nazi, let me say that it IS a fascinating discovery and I’m pleased to know about it. I also can’t tell whether the person in question is Julie Turner or Jia You (who might be excused as a non-native speaker).

      • In reply to #6 by justinesaracen:

        In reply to #5 by Net:

        i’m grateful and interested in the message, but oh how i hate the writing.

        Hypervelocity stars are so called because, uh, they travel really fast

        …And before I am accused of being a grammar Nazi …

        Or Conan the Grammarian ;)

  1. The article mentions that hypervelocity stars are caused by a binary system being torn apart by a black hole, but then continues as if all anyone had known was that hypervelocity stars had to be produced by a supermassive black hole. Could anyone tell me if that has to be a supermassive black hole in order to achieve that speed, or if a conventional black hole or even neutron star would be sufficient to catapult one of the stars? Also, am I right in conceiving it as a result of centrifugal force, like a hammer-thrower building up circular momentum and releasing the grip on the hammer?

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