Andrew Yee[_1_]
May 28th 08, 05:10 PM
ESO Education and Public Relations Dept.
----------------------------------------------------------------------------
Text with all links and the photos are available on the ESO Website at URL:
http://www.eso.org/public/outreach/press-rel/pr-2008/pr-15-08.html
----------------------------------------------------------------------------
Contacts
Keiichi Ohnaka
Max-Planck Institute for Radio Astronomy
Bonn, Germany
Phone: +49-228-525-353
E-mail: kohnaka (at) mpifr-bonn.mpg.de
Markus Wittkowski
ESO, Germany
Phone: +49-89-3200-6769
E-mail: mwittkow (at) eso.org
Dr. Henri Boffin
ESO Press Officer
Phone: +49 89 3200 6222
Valentina Rodriguez
ESO Press Officer in Chile
Phone: +56 2 463 3123
For Immediate Release: 27 May 2008
ESO Science Release 15/08
The Behemoth Has a Thick Belt
Astronomers resolve torus around star in another galaxy
Talk about a diet! By resolving, for the first time, features of an
individual star in a neighbouring galaxy, ESO's VLT has allowed astronomers
to determine that it weighs almost half of what was previously thought,
thereby solving the mystery of its existence. The behemoth star is found to
be surrounded by a massive and thick torus of gas and dust, and is most
likely experiencing unstable, violent mass loss.
WOH G64 is a red supergiant star almost 2 000 times as large as our Sun and
is located 163 000 light-years away in the Large Magellanic Cloud, one of
the Milky Way's satellite galaxies.
"Previous estimates gave an initial mass of 40 times the mass of the Sun to
WOH G64. But this was a real problem as it was way too cold, compared to
what theoretical models predict for such a massive star. Its existence
couldn't be explained," says Keiichi Ohnaka, who led the work on this
object.
New observations, made with ESO's Very Large Telescope Interferometer,
conclude that the gas and dust around the star is arranged in a thick ring,
rather than a spherical shell, and the star is thus less hidden than had
been assumed. This implies that the object is in fact half as luminous as
previously thought, and thus, less massive. The astronomers infer that the
star started its life with a mass of 25 solar masses. For such a star, the
observed temperature is closer to what one would expect.
"Still, the characteristics of the star mean that it may be experiencing a
very unstable phase accompanied by heavy mass loss," says co-author Markus
Wittkowski from ESO. "We estimate that the belt of gas and dust that
surrounds it contains between 3 and 9 solar masses, which means that the
star has already lost between one tenth and a third of its initial mass."
To reach this conclusion, the team of astronomers used the MIDI instrument
to combine the light collected by three pairs of 8.2-m Unit Telescopes of
the VLT. This is the first time that MIDI has been used to study an
individual star outside our Galaxy.
The observations allowed the astronomers to clearly resolve the star.
Comparisons with models led them to conclude that the star is surrounded by
a gigantic, thick torus, expanding from about 15 stellar radii (or 120 times
the distance between the Earth and the Sun -- 120 AU!) to more than 250
stellar radii (or 30 000 AU!).
"Everything is huge about this system. The star itself is so big that it
would fill almost all the space between the Sun and the orbit of Saturn,"
says Ohnaka. "And the torus that surrounds it is perhaps a light-year
across! Still, because it is so far away, only the power of interferometry
with the VLT could give us a glimpse on this object."
Notes
The name WOH G64, refers to the fact that it is the 64th entry in the
catalogue by Westerlund, Olander, and Hedin, published in 1981, and based on
observations made at ESO La Silla.
The team is comprised of K. Ohnaka, T. Driebe, K.-H. Hofmann, G. Weigelt
(Max-Planck Institute for Radio Astronomy, Bonn, Germany), and M. Wittkowski
(ESO).
"Spatially resolved dusty torus toward the red supergiant WHO G64 in the
Large Magellanic Cloud", by K. Ohnaka et al., Astronomy and Astrophysics,
484, 371.
National contacts for the media:
Belgium: Dr. Rodrigo Alvarez, +32-2-474 70 50
Czech Republic: Pavel Suchan, +420 267 103 040
Denmark: Dr. Michael Linden-Vornle, +45-33-18 19 97
Finland: Ms. Riitta Tirronen, +358 9 7748 8369
France: Dr. Daniel Kunth, +33-1-44 32 80 85
Germany: Dr. Jakob Staude, +49-6221-528229
Italy: Dr. Leopoldo Benacchio, +39-347-230 26 51
The Netherlands: Dr. Marieke Baan, +31-20-525 74 80
Portugal: Prof. Teresa Lago, +351-22-089 833
Spain: Dr. Miguel Mas-Hesse, +34918131196
Sweden: Dr. Jesper Sollerman, +46-8-55 37 85 54
Switzerland: Dr. Martin Steinacher, +41-31-324 23 82
United Kingdom: Mr. Peter Barratt, +44-1793-44 20 25
USA: Dr. Paola Rebusco, +1-617-308-2397
----------------------------------------------------------------------------
ESO Press Information is available on Receive email notification
the WWW at about important news from
http://www.eso.org/outreach/press-rel/ ESO - subscribe to the
ESO-NEWS Mailing List.
----------------------------------------------------------------------------
Copyright ESO Education & Public Relations Department
Karl-Schwarzschild-Strasse 2, D-85748 Garching, Germany
----------------------------------------------------------------------------
----------------------------------------------------------------------------
Text with all links and the photos are available on the ESO Website at URL:
http://www.eso.org/public/outreach/press-rel/pr-2008/pr-15-08.html
----------------------------------------------------------------------------
Contacts
Keiichi Ohnaka
Max-Planck Institute for Radio Astronomy
Bonn, Germany
Phone: +49-228-525-353
E-mail: kohnaka (at) mpifr-bonn.mpg.de
Markus Wittkowski
ESO, Germany
Phone: +49-89-3200-6769
E-mail: mwittkow (at) eso.org
Dr. Henri Boffin
ESO Press Officer
Phone: +49 89 3200 6222
Valentina Rodriguez
ESO Press Officer in Chile
Phone: +56 2 463 3123
For Immediate Release: 27 May 2008
ESO Science Release 15/08
The Behemoth Has a Thick Belt
Astronomers resolve torus around star in another galaxy
Talk about a diet! By resolving, for the first time, features of an
individual star in a neighbouring galaxy, ESO's VLT has allowed astronomers
to determine that it weighs almost half of what was previously thought,
thereby solving the mystery of its existence. The behemoth star is found to
be surrounded by a massive and thick torus of gas and dust, and is most
likely experiencing unstable, violent mass loss.
WOH G64 is a red supergiant star almost 2 000 times as large as our Sun and
is located 163 000 light-years away in the Large Magellanic Cloud, one of
the Milky Way's satellite galaxies.
"Previous estimates gave an initial mass of 40 times the mass of the Sun to
WOH G64. But this was a real problem as it was way too cold, compared to
what theoretical models predict for such a massive star. Its existence
couldn't be explained," says Keiichi Ohnaka, who led the work on this
object.
New observations, made with ESO's Very Large Telescope Interferometer,
conclude that the gas and dust around the star is arranged in a thick ring,
rather than a spherical shell, and the star is thus less hidden than had
been assumed. This implies that the object is in fact half as luminous as
previously thought, and thus, less massive. The astronomers infer that the
star started its life with a mass of 25 solar masses. For such a star, the
observed temperature is closer to what one would expect.
"Still, the characteristics of the star mean that it may be experiencing a
very unstable phase accompanied by heavy mass loss," says co-author Markus
Wittkowski from ESO. "We estimate that the belt of gas and dust that
surrounds it contains between 3 and 9 solar masses, which means that the
star has already lost between one tenth and a third of its initial mass."
To reach this conclusion, the team of astronomers used the MIDI instrument
to combine the light collected by three pairs of 8.2-m Unit Telescopes of
the VLT. This is the first time that MIDI has been used to study an
individual star outside our Galaxy.
The observations allowed the astronomers to clearly resolve the star.
Comparisons with models led them to conclude that the star is surrounded by
a gigantic, thick torus, expanding from about 15 stellar radii (or 120 times
the distance between the Earth and the Sun -- 120 AU!) to more than 250
stellar radii (or 30 000 AU!).
"Everything is huge about this system. The star itself is so big that it
would fill almost all the space between the Sun and the orbit of Saturn,"
says Ohnaka. "And the torus that surrounds it is perhaps a light-year
across! Still, because it is so far away, only the power of interferometry
with the VLT could give us a glimpse on this object."
Notes
The name WOH G64, refers to the fact that it is the 64th entry in the
catalogue by Westerlund, Olander, and Hedin, published in 1981, and based on
observations made at ESO La Silla.
The team is comprised of K. Ohnaka, T. Driebe, K.-H. Hofmann, G. Weigelt
(Max-Planck Institute for Radio Astronomy, Bonn, Germany), and M. Wittkowski
(ESO).
"Spatially resolved dusty torus toward the red supergiant WHO G64 in the
Large Magellanic Cloud", by K. Ohnaka et al., Astronomy and Astrophysics,
484, 371.
National contacts for the media:
Belgium: Dr. Rodrigo Alvarez, +32-2-474 70 50
Czech Republic: Pavel Suchan, +420 267 103 040
Denmark: Dr. Michael Linden-Vornle, +45-33-18 19 97
Finland: Ms. Riitta Tirronen, +358 9 7748 8369
France: Dr. Daniel Kunth, +33-1-44 32 80 85
Germany: Dr. Jakob Staude, +49-6221-528229
Italy: Dr. Leopoldo Benacchio, +39-347-230 26 51
The Netherlands: Dr. Marieke Baan, +31-20-525 74 80
Portugal: Prof. Teresa Lago, +351-22-089 833
Spain: Dr. Miguel Mas-Hesse, +34918131196
Sweden: Dr. Jesper Sollerman, +46-8-55 37 85 54
Switzerland: Dr. Martin Steinacher, +41-31-324 23 82
United Kingdom: Mr. Peter Barratt, +44-1793-44 20 25
USA: Dr. Paola Rebusco, +1-617-308-2397
----------------------------------------------------------------------------
ESO Press Information is available on Receive email notification
the WWW at about important news from
http://www.eso.org/outreach/press-rel/ ESO - subscribe to the
ESO-NEWS Mailing List.
----------------------------------------------------------------------------
Copyright ESO Education & Public Relations Department
Karl-Schwarzschild-Strasse 2, D-85748 Garching, Germany
----------------------------------------------------------------------------