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| PRI (MPIfR) 07/2010 (1) | Press Release | July 15, 2010 |
An international research team led by Stefan Kraus with team members
from two research groups of the
Max Planck Institute for Radio Astronomy in Bonn
has been able to obtain the first infrared image of a compact disc
closely encircling a massive young star. This provides strong evidence
that massive stars form in the same way as their smaller brothers -
thereby closing an enduring debate. The discovery, made thanks to a
combination of the Very Large Telescope Interferometer, the APEX
telescope and the New Technology Telescope, is described in an article
in this week's issue of Nature.
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Figure 1:
Left: Artist's impression of a dusty disk encircling a massive young
star; Right: Disk around IRAS 13481-6124. VLTI/AMBER observations combining three 1.8m Auxiliary Telescopes of the VLTI show an image with a resolution
of only 2.4 milliarcseconds.
Images:
ESO/L. Calçada (left); ESO/S. Kraus (right).
(Click image for higher resolution).
The team of astronomers looked at an object, known by the cryptic name of IRAS 13481-6124. About twenty times the mass of our Sun and five times its radius, the young central star, which is still surrounded by a disk, its pre-natal cocoon, is located in the constellation of Centaurus, about 10 000 light-years away. Disks of gas and dust around young stars are the material reservoir from which also planets can form.
"Our observations show a disc surrounding an embryonic young, massive star, which is now fully formed," says Stefan Kraus, who led the study. "One can say that the baby is about to hatch!"
From archival images obtained by the NASA Spitzer Space Telescope as well as from observations done with the APEX 12-metre submillimetre telescope, astronomers discovered the presence of a jet.
"Such jets ejected from young stars, generally indicate the presence of a circumstellar disc", says Karl Menten from the team at the Max-Planck Institute for Radioastronomy (MPIfR) in Bonn. "Radio telescopes like the APEX sub-mm telescope allow us, for the first time, to study outflows at short radio wavelengths in the submillimeter range. The present project brings together the expertise of two research groups at MPIfR, infrared interferometry in order to investigate the structure of the disk and submillimeter astronomy showing the structure of the bipolar outflow."
Circumstellar discs are an essential ingredient in the formation process of low-mass stars such as our Sun. However, it is not known whether this can also account for the formation of stars more massive than about ten solar masses, where the strong stellar light emitted might prevent mass falling onto the star. For instance, it has been proposed that massive stars might form when smaller stars merge.
In order to discover and understand the properties of this disc, astronomers employed ESO's Very Large Telescope Interferometer (VLTI). By combining light from three of the VLTI's 1.8-metre Auxiliary Telescopes with the AMBER instrument, this facility allows astronomers to see details equivalent to those a telescope with a mirror of 85 metres in diameter would see. The resulting resolution is about 2.4 milliarcseconds, which is equivalent to picking out the head of a screw on the International Space Station.
With this unique capability, complemented by observations done with another of ESO's telescopes, the 3.58-metre New Technology Telescope at La Silla, the team was able to detect a disc around IRAS 13481-6124.
"This is the first high-resolution image of the inner disk around a young star, and the combination of infrared interferometry and observations at radio wavelengths allows us to study the important physical connection between discs and outflows", says Gerd Weigelt from the infrared interferometry team at MPIfR. "The new observations suggest that disks play a similar role in the formation process of both low- and high-mass stars."
The astronomers conclude that the system is about 60 000 years old, and that the star has reached its final mass. The disc will soon start to evaporate and eventually form a planetary system. The flared disc extends to about 130 times the Earth-Sun distance - or 130 astronomical units (AU) - and has a mass similar to that of the star, roughly twenty times the Sun.
"Further observations with the Atacama Large Millimeter/submillimeter Array (ALMA), currently being constructed in Chile, could provide much information on these inner parts, and allow us to better understand how baby massive stars became heavy," concludes Stefan Kraus.
In the year 2008, Stefan Kraus was honoured with an Otto Hahn medal for
scientific achievements accomplished with his PhD work at MPIfR.
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Figure 2:
Left:
VLTI at Cerro Paranal, Chile with domes of the 1.8 m Auxiliary Telescopes
(AT) in the foreground;
Right:
APEX submillimeter telescope, located at an altitude of 5100 m
at Chajnantor (Chile);
Images: S. Kraus, MPIfR.
(Click image for higher resolution).
The European Southern Observatory (ESO), is the foremost intergovernmental astronomy organisation in Europe and the world's most productive astronomical observatory. It is supported by 14 countries: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor.
The Atacama Pathfinder EXperiment (APEX) is a 12-meter telescope, located at 5100 m altitude on the arid plateau of Chajnantor in the Chilean Andes. APEX operates at millimeter and submillimeter wavelengths. This wavelength range is a relatively unexplored frontier in astronomy, requiring advanced detectors and an extremely high and dry observatory site, such as Chajnantor. APEX, the largest submillimeter-wave telescope operating in the southern hemisphere, is a collaboration between the Max-Planck-Institut für Radioastronomie, the Onsala Space Observatory and ESO. Operation of APEX at Chajnantor is entrusted to ESO.
The Very Large Telescope Interferometer (VLTI) utilizes telescopes at
ESO's Paranal site, either the 8.2 m UTs or the 1.8m ATs (Auxiliary Telescopes).
AMBER (Astronomical Multi-BEam Recombiner) is one of the science instruments of the VLTI. It is an interferometric beam combiner, sensitive in the near-infrared wavelength range (from 1 to 2.5 microns), built in collaboration with institutes from Grenoble (Laboratoire d'Astrophysique de Grenoble), Nice (Laboratoire d'Astrophysique Universitaire de Nice und Observatoire de la Côte d'Azur), Florence (Observatorio Astrofisico di Arcetri) and Bonn (Max Planck Institute for Radio Astronomy).
A hot compact dust disk around a massive young stellar object
,
Stefan Kraus, Karl-Heinz Hofmann, Karl M. Menten, Dieter Schertl,
Gerd Weigelt, Friedrich Wyrowski, Anthony Meilland, Karine Perrault,
Romain Petrov, Sylvie Robbe Dubois, Peter Schilke, Leonardo Testi,
2010, Nature, 466, 339-342. doi:10.1038/nature09174.
Unravelling the Mystery of Massive Star Birth , ESO Science Release 1029, from July 14, 2010. All Stars are Born the Same Way.
Blick in die Wiege eines Sterns , MPG SP / 2010 (172), from July 14, 2010. Max-Planck-Forscher enthüllen mit interferometrischen Beobachtungen die geheimnisvolle Geburt massereicher Sonnen.
Meet the Titans: Dust Disk Found Around Massive Star ,
JPL News 2010-235, from July 14, 2010.
Max Planck Institute for Radio Astronomy (MPIfR) .
Infrared Interferometry Group at MPIfR .
Astronomy Department (University of Michigan).
European Southern Observatory (ESO).
Astronomical Multi-BEam combineR (AMBER).
Atacama Pathfinder EXperiment
(APEX).
Prof. Dr. Gerd Weigelt,
Head of Research Group "Infrared Interferometry".
Max-Planck-Institut für Radioastronomie, Bonn.
Fon: +49-228-525-243
E-mail: gweigelt (at)
mpifr-bonn.mpg.de
Dr. Stefan Kraus,
Astronomy Department, University of Michigan, USA.
Fon: +1-734-615-7374
E-mail: stefankr (at)
umich.edu
Dr. Norbert Junkes,
Public Outreach,
Max-Planck-Institut für Radioastronomie, Bonn.
Fon: +49-228-525-399
E-mail: njunkes (at)
mpifr-bonn.mpg.de