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Yahoo! News Story - Bursts Spotted at Milky Way's Black Hole - Yahoo! News

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  • Mark Holmes
    Mark Holmes (mahtezcatpoc@yahoo.com) has sent you a news article. (Email address has not been verified.) ... Personal message: Bursts Spotted at Milky
    Message 1 of 2 , Nov 18, 2008
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      Mark Holmes (mahtezcatpoc@...) has sent you a news article.
      (Email address has not been verified.)
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      Bursts Spotted at Milky Way's Black Hole - Yahoo! News

      http://news.yahoo.com/s/space/20081118/sc_space/burstsspottedatmilkywaysblackhole

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    • mahtezcatpoc
      ... http://news.yahoo.com/s/space/20081118/sc_space/burstsspottedatmilkywa ysblackhole SPACE.com Space.com Staff space.com – 2 hrs 44 mins ago Outbursts from
      Message 2 of 2 , Nov 18, 2008
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        --- In thefixedstars@yahoogroups.com, Mark Holmes <mahtezcatpoc@...>
        wrote:
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        > Mark Holmes (mahtezcatpoc@...) has sent you a news article.
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        > Bursts Spotted at Milky Way's Black Hole - Yahoo! News
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        http://news.yahoo.com/s/space/20081118/sc_space/burstsspottedatmilkywa
        ysblackhole



        SPACE.com Space.com Staff

        space.com – 2 hrs 44 mins ago

        Outbursts from the black hole at the center of our Milky Way galaxy
        generate material that is stretched as it orbits near the
        gravitational behemoth.


        New observations from two telescopes provide a better look at what's
        going on down there.


        While black holes can't be seen, material swirling into one is
        superheated, giving off radiation that can be observed. While the
        Milky Way's black hole is not among the most active in the universe,
        it is prone to flare-ups.


        A team of European and US astronomers used ESO's Very Large Telescope
        (VLT) and the Atacama Pathfinder Experiment (APEX) telescope, both in
        Chile, to study light from the black hole, called Sagittarius A*, at
        near-infrared wavelengths and the longer submillimeter wavelengths
        respectively.


        This is the first time that astronomers have recorded an outburst
        with these telescopes simultaneously.


        "Observations like this, over a range of wavelengths, are really the
        only way to understand what's going on close to the black hole," said
        Andreas Eckart of the University of Cologne, who led the team.


        Sagittarius A* is about 26,000 light-years away. It is a supermassive
        black hole with a mass of about 4 million times that of the sun.
        Most, if not all, galaxies are thought to have a supermassive black
        hole in their centers.


        "Sagittarius A* is unique, because it is the nearest of these monster
        black holes, lying within our own galaxy," said team member Frederick
        K. Baganoff of MIT. "Only for this one object can our current
        telescopes detect these relatively faint flares from material
        orbiting just outside the event horizon."


        The emission from Sagittarius A* is thought to come from gas thrown
        off by stars, which then orbits and falls into the black hole.


        The researchers detected violently variable infrared emission, with
        four major flares over a six-hour period. The submillimeter-
        wavelength results showed flares that began more than an hour after
        the infrared flares.


        The researchers explain that this time delay is probably caused by
        the rapid expansion, at speeds of about 3.1 million mph (5 million
        kph), of the clouds of gas that are emitting the flares. This
        expansion causes changes in the character of the emission over time.


        The material was moving at only 0.5 percent of the speed of light. To
        escape from the very strong gravity so close to the black hole, the
        gas would have to be traveling at half the speed of light — 100 times
        faster than detected –- and so the researchers believe that the gas
        cannot be streaming out in a jet. Instead, they suspect that a blob
        of gas orbiting close to the black hole is being stretched out, like
        dough in a mixing bowl, and this is causing the expansion.
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