The dusty ring around the aging double star IRAS 08544-4431
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The aging double star IRAS 08544-4431 in the constellation of Vela (The Sails)
The rich celestial landscape around the aging double star IRAS 08544-4431
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VLTI finds discs around aging stars similar to those around young ones
The Very Large Telescope Interferometer
at ESO’s Paranal Observatory in Chile has obtained the sharpest view
ever of the dusty disc around an aging star. For the first time such
features can be compared to those around young stars — and they look
surprisingly similar. It is even possible that a disc appearing at the
end of a star’s life might also create a second generation of planets.
As they approach the ends of their lives many stars develop stable
discs of gas and dust around them. This material was ejected by stellar winds, whilst the star was passing through the red giant
stage of its evolution. These discs resemble those that form planets
around young stars. But up to now astronomers have not been able to
compare the two types, formed at the beginning and the end of the
stellar life cycle.
Although there are many discs associated with young stars that are
sufficiently near to us to be studied in depth, there are no
corresponding old stars with discs that are close enough for us to
obtain detailed images.
But this has now changed. A team of astronomers led by Michel Hillen and Hans Van Winckel from the Instituut voor Sterrenkunde in Leuven, Belgium, has used the full power of the Very Large Telescope Interferometer (VLTI) at ESO’s Paranal Observatory in Chile, armed with the PIONIER instrument, and the newly upgraded RAPID detector.
Their target was the old double star IRAS 08544-4431 [1], lying about 4000 light-years from Earth in the southern constellation of Vela (The
Sails). This double star consists of a red giant star, which expelled
the material in the surrounding dusty disc, and a less-evolved more
normal star orbiting close to it.
Jacques Kluska, team member from Exeter University, United Kingdom, explains: “By
combining light from several telescopes of the Very Large Telescope
Interferometer, we obtained an image of stunning sharpness — equivalent
to what a telescope with a diameter of 150 metres would see. The
resolution is so high that, for comparison, we could determine the size
and shape of a one euro coin seen from a distance of two thousand
kilometres.”
Thanks to the unprecedented sharpness of the images [2]
from the Very Large Telescope Interferometer, and a new imaging
technique that can remove the central stars from the image to reveal
what lies around them, the team could dissect all the building blocks of
the IRAS 08544-4431 system for the first time.
The most prominent feature of the image is the clearly resolved ring.
The inner edge of the dust ring, seen for the first time in these
observations, corresponds very well with the expected start of the dusty
disc: closer to the stars, the dust would evaporate in the fierce
radiation from the stars.
“We were also surprised to find a fainter glow that is probably
coming from a small accretion disc around the companion star. We knew
the star was double, but weren’t expecting to see the companion
directly. It is really thanks to the jump in performance now provided by
the new detector in PIONIER, that we are able to view the very inner
regions of this distant system,” adds lead author Michel Hillen.
The team finds that discs around old stars are indeed very similar to
the planet-forming ones around young stars. Whether a second crop of
planets can really form around these old stars is yet to be determined,
but it is an intriguing possibility.
“Our observations and modelling open a new window to study the
physics of these discs, as well as stellar evolution in double stars.
For the first time the complex interactions between close binary systems
and their dusty environments can now be resolved in space and time,” concludes Hans Van Winckel.
Notes
[1] The name of the object indicates that it is a source of infrared radiation that was detected and catalogued by the IRAS satellite observatory in the 1980s.
[2] The resolution of the VLTI, used with the four Auxiliary Telescopes, was about one milliarcsecond (1/1000th of 1/3600th of a degree).
More Information
This research was presented in a paper entitled “Imaging the dust sublimation front of a circumbinary disk”, by M. Hillen et al., to appear as a letter in the journal Astronomy & Astrophysics.
The team is composed of M. Hillen (Instituut voor Sterrenkunde, Leuven, Belgium), J. Kluska (University of Exeter, Exeter, United Kingdom), J.-B. Le Bouquin (UJF-Grenoble 1/CNRS-INSU, Institut de Planétologie et d’Astrophysique de Grenoble, France), H. Van Winckel (Instituut voor Sterrenkunde, Leuven, Belgium), J.-P. Berger (ESO, Garching, Germany), D. Kamath (Instituut voor Sterrenkunde, Leuven, Belgium) and V. Bujarrabal (Observatorio Astronómico Nacional, Alcalá de Henares, Spain).
ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.
Links
- Research paper
- Further information about PIONIER, and the new RAPID detector
- Photos of the VLT
Contacts
Hans Van Winckel
Instituut voor Sterrenkunde
KU Leuven, Belgium
Tel: +32 16 32 70 32
Richard Hook
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org
Source: ESO