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					            MAX PLANCK SOCIETY
                                                                Press Release
News SP / 2007 (136)                                        September 14th, 2007

          Why is the Hercules Dwarf Galaxy so flat?
  First accepted refereed publication based on observations with the new
                        Large Binocular Telescope

Through some of the very first scientific observations with the brand-new
Large Binocular Telescope (LBT) in Arizona, an international team of
astronomers has found that a recently discovered tiny companion galaxy to
our Milky Way, named the Hercules Dwarf Galaxy, has truly exceptional                  Max Planck Society
properties: while basically all of its known peers in the realm of these tiny          for the Advancement of Science
                                                                                       Press and Public Relations Department
dwarf galaxies are rather round, this galaxy at a distance of 430,000 Light
Years appears highly flattened, either the shape of a disk or of a cigar.              Hofgartenstrasse 8
                                                                                       D-80539 Munich
                                                                                       Germany

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                                                                                       Phone: +49-89-2108-1276
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                                                                                       Responsibility for content:
                                                                                       Dr. Bernd Wirsing (-1276)




                                                                                       ISSN 0170-4656




Fig. 1:   The Hercules Dwarf Galaxy has truly exceptional properties: while
          basically all of its known peers in the realm of these tiny dwarf galaxies
          are rather round, this galaxy at a distance of 430,000 Light Years
          appears highly flattened, either the shape of a disk or of a cigar.

                                                         Image: LBT Corporation

The stars in many large galaxies are arranged in a disk-like configuration, as in
our own Milky Way. Yet in smaller galaxies like the Hercules Dwarf, which
despite its name has only a 10-millionth as many stars as the Milky Way, a disk-
like configuration has never been observed before. Among the millions of well-
studied galaxies none has ever been observed to have a cigar-like shape.
                                                       2


An explanation for the galaxy’s unusual shape is that it is being disrupted by the gravitational forces of the
Milky Way. This effect is definitely seen in another of the Milky Way's satellites, the Sagittarius Dwarf.
Yet, this object is 10 times closer to the Milky Way’s centre than the Hercules Dwarf Galaxy, and hence
more highly affected by the destructive "tidal forces" of our Galaxy. The Hercules Dwarf Galaxy can only
have experienced a similar fate if its orbit would have brought it exceptionally close to the inner parts of the
Milky Way. So, "The Hercules Dwarf Galaxy is either unlike any of the millions of galaxies studied so far,
or circles our Galaxy on an extremely plunging orbit: an exceptional, unparalleled object at any rate", says
Matthew Coleman of the Max Planck Institute for Astronomy in Germany, who headed this study.
The world’s single biggest telescope
These inferences were enabled by the very deep images provided by the brand-new Large Binocular
Telescope (LBT), the largest single telescope in the world, which is located on the 3190-metre high Mount
Graham in Arizona. Two giant mirrors with a diameter of 8.4 meters each, are hosted on the same mount
acting as gigantic field glasses.




Fig. 2:   The Large Binocular Telescope (LBT) in Arizona, USA.

                                                                                      Image: LBT Corporation

The pictures of the Hercules Dwarf Galaxy were created using the high-tech Large Binocular Camera (LBC-
Blue), mounted at the Prime Focus of one of the two 8.4-metre mirrors. LBC-Blue and its future twin for
the red spectral range, LBC-red, are being developed by Italian partners in the project. The camera and
telescope work together like a giant digital camera which is able to capture images of ultra-faint objects with
a field of view the size of the full moon. "I am delighted to see that the new camera is delivering such exciting
images to the Astronomy community, off the bat," says Emanuele Giallongo of INAF/Rome, who built the
camera. "We provided early ‘science demonstration time’ to our astronomers," says Richard Green, LBT
Director, "so that they could show what can be done with this new facility. This result is just the first, with
many more to come."
New chances to study distant planets, stars and galaxies
By combining the optical paths of the two individual mirrors, the LBT will collect in its final increment as
much light as a telescope whose mirrors have a diameter of 11.8 meters. This is a factor of 24 larger than
the 2.4-metre mirror of the Hubble Space Telescope. Even more importantly, the LBT will then have the
resolution of a 22.8-metre telescope, because it will use the most modern adaptive optics, superimposing
pictures with an interferometric procedure. The astronomers are thus able to compensate for the blurring
                                                      3


caused by air turbulence. With that power, the LBT will open completely new possibilities in researching
planets outside the solar system and the investigation of the faintest and most distant galaxies.
The LBC camera is the first of a suite of high-tech instruments with which the LBT will be equipped in the
future. These additional instruments include spectrographs with different resolution and spectral sensitivity
as well as very complex instruments which will combine the light path of the two giant main mirrors. Both
the telescope and instruments are being built by an international collaboration among institutions in the
United States, Italy and Germany.
The Partners in the LBT Corporation (LBTC) are:
   • University of Arizona, USA;
   • Istituto Nazionale di Astrofisica, Italy
   • LBT Beteiligungsgesellschaft (LBTB), Germany
     (Max Planck Society, Astrophysical Institute Potsdam, University of Heidelberg);
   • Ohio State University, USA
   • The Research Corporation, USA
     (University of Notre Dame, University of Minnesota and University of Virginia)
Due to the impressive first pictures and results, the astronomers are now very confident that the $120 million
project is on the way to open a new door for spectacular observations of planets, stars and galaxies.
The German partners are coordinated by the Max Planck Institute for Astronomy, Heidelberg, participating
in 25 percent of the observation time on the LBT-Project.
********************************
The complete list of author of the publication on the Hercules dwarf galaxy:
Matthew G. Coleman (Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany)
Jelte T. A. de Jong (Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany)
Nicolas F. Martin (Max-Planck-Institut für Astronomie, Königstuhl 17,D-69117 Heidelberg, Germany)
Hans-Walter Rix (Max-Planck-Institut für Astronomie, Königstuhl 17,D-69117 Heidelberg, Germany)
David J. Sand (Chandra Fellow, Steward Observatory, The University of Arizona, Tucson, AZ 85721)
Eric F. Bell (Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany)
Richard W. Pogge (Dep. of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH
43210-1173)
David J. Thompson (Large Binocular Telescope Observatory, Univ. of Arizona, 933 N. Cherry Ave., Tucson,
AZ 85721-0065)
H. Hippelein (Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany)
E. Giallongo (INAF, Osservatorio Astronomico di Roma, via Frascati 33, I-00040 Monteporzio, Italy)
R. Ragazzoni (INAF, Osservatorio Astronomico di Roma, via Frascati 33, I-00040 Monteporzio, Italy)
Andrea DiPaola (INAF, Osservatorio Astronomico di Roma, via Frascati 33, I-00040 Monteporzio, Italy)
Jacopo Farinato (INAF, Osservatorio Astronomico di Padova, vicolo dell'Osservatorio, 5, 35122 Padova,
Italy)
Riccardo Smareglia (INAF, Osservatorio Astronomico di Trieste, via G.B. Tiepolo, 11, 34131 Trieste, Italy)
Vincenzo Testa (INAF, Osservatorio Astronomico di Roma, via Frascati 33, I-00040 Monteporzio, Italy)
Jill Bechtold (Steward Observatory, The University of Arizona, Tucson, AZ 85721)
John M. Hill (Large Binocular Telescope Observatory, Univ. of Arizona, 933 N. Cherry Ave., Tucson, AZ
85721-0065)
Peter M. Garnavich (Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge MA 02138)
Richard F. Green (Large Binocular Telescope Observatory, Univ. of Arizona, 933 N. Cherry Ave., Tucson,
AZ 85721-0065)
Related Links:
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[1]        The LBT Website

[2]        Further high resolution images of various astronomical objects, which have been recently captured by the LBT

[3]        Coleman and his team will publish their results in the Astrophysical Journal Letters

[4]        The German version of the press release

Contact:

      Dr. Matthew Coleman
      Max Planck Institute for Astronomy, Heidelberg
      Tel.: +49 6221 528-412
      E-mail: coleman@mpia.de

      Dr. Klaus Jäger
      Max Planck Institute for Astronomy, Heidelberg
      Tel.: +49 6221 528-379
      E-mail: jaeger@mpia.de

				
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