One question for all about black holes(for experts,if possible)...

Discussion in 'Astronomy, Exobiology, & Cosmology' started by Gravage, Feb 11, 2005.

  1. Gravage Registered Senior Member

    Messages:
    1,241
    Here some already very old news:
    A bunch of stars only 2 light weeks away were rotating around the Milky Way galaxy's dark center with a speed over 1400 km/s.
    Than we had a star named S2 who was only on its ecliptic way around the central black hole,the closest it got was 17 light hours and its speed was over 5000 km/s...
    My question is

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    oes great speed of stars and all other forms of matter mean that there is a giant,supermassive black hole,in the centre of our Milky Way galaxy?Are speed of stars or magnetic fields and etc. reliable proofs that there is indeed giant,supermassive black hole in the centre of our Milky Way galaxy?

    I'm asking this because:
    Earth’s circumference at the equator is 25,000 miles or 40,000 kilometers, divided by 24 hours is the equivalent to over 1000 miles or 1609 kilometers speed per hour.

    Multiply by the cosine of your latitude to see how fast the Earth is rotating where you are.

    While Planet Earth is rotating on its axis at the speed of over 1000 miles or 1609 kilometers per hour, Earth is also traveling, revolving on its oval orbit around the Sun at the speed of about 67,000 miles or 107,200 kilometers per hour once every 365 days or one whole year.

    The Sun is about 27,000 light years away from the center of the Galaxy, rotating with a speed of about 220 kilometers per second. We determine this using measurements of the relative motions of stars in the "halo" of our Galaxy. The halo is made up of old stars, and doesn't rotate as a whole. As the Sun orbits the Galaxy, therefore, we tend to be approaching halo stars in one direction, and moving away from them in the other. By measuring the speed with which we are approaching some and moving away from others, we measure the speed with which we are moving around the center of the Galaxy, approx. 792,000 kilometers per hour.

    When you're talking about 1400 km/sec, then it is "only" six times faster than we, on our own planet are moving around the galaxy(note this only 2 light weeks away from the Milky Way's central black hole)),and 5000 km/s almost only 22 times(actually is 21,7391 times,and note that it is only 17 light hours away from the Milky Way's central black hole)) than our planet that is moving around the galaxy... Still - we don't burn up...

    These speeds are NOTHING compared to a speed of 300,000 km/sec of light.

    My question/point is:Shouldn't stars that are only 2 light weeks or only 17 light hours from the Milky Way's central black hole should orbit black hole much,much faster than our solar system is orbiting around the center of the galaxy,which faaar further than mere 2 light weeks?
    Thanks,everyone!
     
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  3. eburacum45 Valued Senior Member

    Messages:
    1,297
    This is a very interesting question, and an excellent observation!
    However you are actually asking slightly the wrong question.
    The orbital velocity of the stars and other matter in the vicinty of the supermassive black hole SaA is entitrely consistent with the mass of that object; in fact this motion has allowed us to estimate the mass of that object.

    What is not easy to explain is the orbital velocity of the Sun and all the other stars in our vicinity. Our galactic orbital speed is dictated by all the mass between us and the central black hole, as well as the central black hole itself; but we are apparently moviong too fast for this velocity to be explained by the visible mass in this region.
    It is as if there was a considerable amount of invisible mass in this region, detectable only by its gravitational pull.
    This missing mass is the famous dark matter; there is your mystery, and it has not yet been resolved.
     
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  5. Maddad Time is a Weighty Problem Registered Senior Member

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    That is a good focus on the problem, eburacum45.
     
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