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Why the excess of young stars close to Milky's supermassive BH?

  1. Jul 15, 2008 #1


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    I happened to see this and thought someone here might be interested
    It has been accepted for publication in Astrophysical Journal and it suggests a reason for something I didnt know about---there are unexpectedly many young stars clustered around the vicinity of the SMBH at the center of our galaxy.

    some nice animations of the stars orbiting the SMBH are available, we had a thread about that several years back
    if I remember correctly, the SMBH is about 2-3 million solar masses. that part is old news.

    BTW I think is impressive that they can observe in there, in the heart of the galaxy and see individual stars. But mostly it strikes me as curious that there should be an excess of very young ones. These authors propose a possible reason

    Origin of the S-Stars in the Galactic Center
    Ulf Löckmann, Holger Baumgardt, Pavel Kroupa
    4 pages, 4 figures, accepted for publication in ApJ Letters
    (Submitted on 14 Jul 2008)
    "Over the last 15 years, around a hundred very young stars have been observed in the central parsec of our Galaxy. While the presence of young stars forming one or two stellar discs at approx. 0.1 pc from the super-massive black hole (SMBH) can be understood through star formation in accretion discs, the origin of the S-stars observed a factor of ten closer to the SMBH has remained a major puzzle. Here we show the S-stars to be a natural consequence of dynamical interaction of two stellar discs at larger radii. Due to precession and Kozai interaction, individual stars achieve extremely high eccentricities at random orientation. Stellar binaries on such eccentric orbits are disrupted due to close passages near the SMBH, leaving behind a single S-star on a much tighter orbit. The remaining star may be ejected from the vicinity of the SMBH, thus simultaneously providing an explanation for the observed hyper-velocity stars in the Milky Way halo."

    I have no special knowledge about this, so I can't comment myself. But thought other people might be interested.
  2. jcsd
  3. Jul 15, 2008 #2


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    Marcus, massive objects can be ejected from the centers of galaxies via gravitational slingshot or perhaps radiation recoil. The disruption (sudden mass ejection in a highly-dense region of a galaxy) might trigger rapid star-formation. Sudden mass discrepancies could encourage rapid accretion of otherwise smoothly- distributed materials and allow new stars to light up.

    Modern cosmology concentrates on gravitation, mergers, etc, and for the most part ignores the possible role of galactic ejection in spawning new bodies. Galactic dynamics is really tough. We live for a very short time, and galaxies can span billions of years. Even with the large sample that we can access, our scientific basis is VERY thin.
    Last edited: Jul 15, 2008
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