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Re: Yahoo! News Story - Infant Stars Caught Feeding - Yahoo! News

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  • mahtezcatpoc
    ... Infant Stars Caught Feeding Andrea Thompson Senior Writer SPACE.com – Tue Oct 14, 7:02 am ET The European Southern Observatory s Very Large Telescope
    Message 1 of 2 , Oct 21, 2008
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      > Infant Stars Caught Feeding - Yahoo! News
      > http://news.yahoo.com/s/space/20081014/sc_space/infantstarscaughtfeeding

      Infant Stars Caught Feeding

      Andrea Thompson
      Senior Writer
      SPACE.com – Tue Oct 14, 7:02 am ET

      The European Southern Observatory's Very Large Telescope has given
      astronomers their most detailed look at how infant stars feed off the
      disks of gas and dust that swirl around them as they grow.

      Galaxies have regions where large amounts of gas and dust are
      concentrated. If the gas is cold and dense enough, clouds of it will
      collapse and begin to form stars. The stars continue to feed off the
      surrounding gas as they grow. The disk of dust and gas can also give
      rise to a planetary system, as it did in our own solar system.

      Observing young stars can help astronomers better understand the
      processes that control star formation, but the closest star-forming
      regions to us are about 500 light-years away. Their great distance
      makes these gas disks appear very small in Earth's sky, so specialized
      techniques must be used to look for fine details in the structures.

      An international group of astronomers used two such techniques to
      probe the inner gaseous environments of six young stars belonging to
      the family of Herbig Ae/Be objects, which are a few times the size of
      our sun and still growing. The findings are detailed in the October
      issue of the journal Astronomy & Astrophysics.

      Two techniques

      One of the best ways to resolve far-away features is interferometry, a
      technique that combines the light of two or more telescopes so that
      the level of detail corresponds to what would be seen by a telescope
      with a diameter equal to the separation between the two telescopes,
      which can be hundreds of feet apart.

      The Very Large Telescope Interferometer (VLTI) has allowed astronomers
      to achieve a resolution of about a milli-arcsecond, an angle
      equivalent to the size of the period at the end of this sentence seen
      from a distance of 31 miles (50 kilometers).

      The astronomers combined interferometry with spectroscopy, or
      splitting light into its constituent colors, to examine the gas
      emission processes around the young stars, which can be linked to the
      physical processes involved in the stars' formation. Astronomers have
      long debated what exactly causes these gas emissions.

      "The origin of gas emissions from these young stars has been under
      debate until now, because in most earlier investigations of the gas
      component, the spatial resolution was not high enough to study the
      distribution of the gas close to the star," said study co-leader
      Stefan Kraus from the Max Planck Institute for Radio Astronomy in
      Germany. "By combining spectroscopy and interferometry, the VLTI has
      given us the opportunity to distinguish between the physical
      mechanisms responsible for the observed gas emission."

      Gas emissions

      Most interferometry so far has studied only the dust that closely
      surrounds the young stars, but astronomers wanted to get a closer look
      at the gas in the same region because "dust is only one percent of the
      total mass of the disks. Their main component is gas, and its
      distribution may define the final architecture of planetary systems
      that are still forming," said Eric Tatulli of the Observatoire de
      Grenoble in France and also a co-leader of the study.

      Two processes were suspected to be behind the gas emissions observed
      coming from the disk: material falling onto the star and gas being
      ejected as a wind from the disk. The study found evidence of both.

      Of the six stars examined, two showed evidence of infalling material.
      Four other stars showed evidence of mass outflow, either as an
      extended stellar wind or as wind coming from the disks surrounding the

      For one of the stars, it seemed that dust might be present closer to
      the star than was expected. The dust is so close that the temperature
      should be high enough for it to evaporate, but since that was not seen
      to be the case, astronomers suspect that the gas in the area shields
      the dust from the star's light.

      The new observations have shown that it is possible to study gas in
      the disks around young stars, and future observations could yield even
      more valuable information about how stars form.

      "Future observations using VLTI spectro-interferometry will allow us
      to determine both the spatial distribution and motion of the gas, and
      might reveal whether the observed line emission is caused by a jet
      launched from the disk or by a stellar wind," Kraus said.

      The study was partly funded by a grant from the Italian National
      Institute for Astrophysics, as well as the Agence Nationale de la
      Recherche (ANR) of France and by the Programme National de Physique
      Stellaire (PNPS).
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