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             Information from the European Southern Observatory

ESO Press Release 14/03

11 June 2003                                               [ESO Logo]

For immediate release
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Flattest Star Ever Seen

Part 2 of 2

Outlook

This new measurement provides a fine example of what is possible with
the VLT Interferometer already at this stage of implementation. It
bodes well for the future research projects at this facility.

With the interferometric technique, new research fields are now
opening which will ultimately provide much more detailed information
about the shapes, surface conditions and interior structure of
stars. And in a not too distant future, it will become possible to
produce interferometric images of the disks of Achernar and other
stars.

More information

The research described in this press release is presented in a Letter
to the Editor, soon to appear in the European research journal
Astronomy & Astrophysics ("The spinning-top Be star Achernar from
VLTI-VINCI" by Armando Domiciano de Souza et al.).

Notes

[1] The team consists of Armando Domiciano de Souza, Lyu Abe and
Farrokh Vakili (Laboratoire Univ. d'Astrophysique de Nice - LUAN,
France), Pierre Kervella (ESO-Santiago), Slobodan Jankov
(Observatoire de la Cote d'Azur, Nice, France), Emmanuel DiFolco and
Francesco Paresce (ESO-Garching).

[2] More information about the VLTI and photos of many of the
components of the facility are available at the VLTI website, as well
as in ESO PR 06/01 ("First Light" in March 2001 and explanation of
the interferometric measurements), ESO PR 23/01 (observations with
two 8.2-m telescopes in October 2001) and ESO PR 16/02 (observations
with four 8.2-m telescopes in September 2002), ESO PR 22/02
(measurements of the diameters of small stars in November 2002) and
ESO PR 11/03 (installation of the first MACAO adaptive optics unit in
May 2003). 

[3] Strictly speaking, the elliptical shape shown in PR Photo 15b/03
is the best fit to the interferometric data, assuming that Achernar
is a uniformly illuminated ellipsoidal body. In fact, the true shape
of the star's photosphere (visible "surface") may be slightly
different in the presence of a light-emitting circumstellar envelope.
However, the astronomers monitored the star's emission for signs of
such an envelope (an "equatorial disk") during the VLTI observations;
there were no signs and they were therefore able to establish narrow
limits on the possible influence of this effect on the apparent
flatness of the star.

[4] The mean angular diameter of Achernar is equivalent to the angle
subtended by a 1 Euro coin at a distance of about 2500 km, or by a
car (4 metres long) on the surface of the Moon.

Contacts

Armando Domiciano de Souza
Laboratoire Univ. d'Astrophysique de Nice (LUAN)
France
Phone: +33 4 9340 5372
Email: armando.domiciano{at}obs-azur.fr

Pierre Kervella
ESO
Santiago de Chile
Phone: +56 2 463 3000
Email: pkervella{at}eso.org

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