Garching (European Southern Observatory): An international team of astronomers has studied with the Very Large Telescope of ESO, the short-lived disk of matter around a young star in the just created a planetary system. For the first time a companion could be detected, which might be responsible for a large gap in the disk. Further observations should show whether it is the companion to a planet or a brown dwarf.planets form in dust disks around young stars, which are a remnant of star formation. The development of such a disk into a mature planetary system, however, is relatively faster, so that only very few objects known in this phase of development [1]. One of them is T Chamaeleontis (abbreviated T Cha), just a faint star in the constellation Chamaeleon small in the southern sky, 330 light years from Earth. T Cha is a sun-like star that is just at the beginning of his life [2]: it is only about 7 million years old (for comparison, the sun is about 4.7 billion years old). Until now we have in such "protoplanetary disks" around young stars can not see straight in nascent planet. In more developed slices this was against already succeeded (eso0842, heic0821).
"Previous studies show that T Cha could be a worthy goal, if you want to investigate how planetary systems arise, "comments Johan Olofsson from the Max-Planck-Institute for Astronomy in Heidelberg. He is one of the first authors of two papers in the journal Astronomy & Astrophysics, describing the new results. "However, T Cha is relatively far away from us. Therefore, we need powerful tools such as the Very Large Telescope Interferometer (VLTI), to be able to resolve to prove the details and what is happening in the dust disk in front of him. "
The astronomers observed T Cha, first with the instrument AMBER at the VLT Interferometer (VLTI ) [3]. They found that part of the disc material has formed a thin dust ring at a distance of only 20 million kilometers from the star. Behind the inner part of the disk, they discovered an area that is free of dust. The outer part of the disk starts at a distance of about 1.1 billion miles from the star.
Nuria Huelamo by the English Centro de Astrobiología and from ESAC, the first author of the second publication, reports on how it went: "The gap in the dust disk around T Cha was for us a clear indication. Apparently we had first observed directly, as a companion of the star digs in the protoplanetary disk a trail. "
a faint companion observed, which is as close to a much brighter star, is a major challenge. To achieve this goal, the team had the VLT NACO instrument in the novel, especially suitable for observations of this kind "Sparse Aperture masking mode use [4]. After careful analysis of the data, the astronomers actually found a clear signal of an object in the gap of the disk, near the outer edge of the disk at a distance of about a billion miles from the star - equivalent to just over the distance of Jupiter from the sun. This is the first direct evidence of an object is much smaller than a star and is in a gap in the protoplanetary Dust disk around a young star is. There are indications that the companion can be a normal star [5], but either a brown dwarf [6], which is surrounded by dust, or - which would of course be very interesting - a planet that has only recently formed.
"This study has combined in a remarkable manner, the data from two different Hochleitstungsinstrumenten at the Paranal Observatory. With future observations, we want to know more about the companion and the disk in experience and clarify, for example, the question of where the dust in the inner area of the disc is "concludes Huelamo.
endnotes
[1] discs in the transitional phase are identified by their reduced emission in the mid-infrared. Explains the lower emission by resolution of the dust near the star and the formation of gaps and holes. Planets that have recently formed the first may create these gaps, but there are other possible causes of development.
[2] T Cha is a so-called T Tauri star, a very young to contract after the prototype T Tauri star named, who is in the process, has in its core area but fired no nuclear fusion.
[3] The astronomers used the AMBER instrument (AMBER stands for Astronomical Multi-Beam Combine, literally as "astronomical instrument for the combination of several light rays") at the Very Large Telescope Interferometer (VLTI), which operates in the near infrared, reaching angular resolutions down to 2 mas, the light from all four VLT Unit Telescopes to a virtual telescope combine to 130m in diameter. It also has moderate spectral resolution. AMBER was by a consortium of several French and Italian institutes and the Max Planck Institute for Radio Astronomy in Bonn in collaboration with ESO and built.
[4] The infrared instrument NACO consists of two components: the adaptive optics system NAOS (Nasmyth Adaptive Optics System) and CONICA (Coude Near-Infrared Camera), a combination of camera and spectrograph, which respectively developed by a French consortium and by the Max-Planck-Institutes for Astronomy in Heidelberg and for Extraterrestrial Physics in Garching in cooperation with the ESO were. With adaptive optics, interference effects can Elimi, caused by the Earth's atmosphere, so the sharpness of astronomical images significantly improved.
The team used the new NACO "Sparse Aperture masking" mode (SAM) to search for the companion. With this special Interferometriemethode instead of the light of several telescopes (as with the VLTI) light, the (in this case it goes to the main telescope VLT-4) in various parts of the level of a single telescope is combined. The new technology is particularly well suited to find faint objects brighter in the immediate vicinity of a lot. The VLTI and AMBER are better suited to the structure of the inner regions of the disk to study are not quite as sensitive when it comes to the direct detection of a companion is
[5] The astronomers studied with NACO for the two different spectral companion: one at 2.2 microns and one at 3.8 microns. Prove he was only at the longer wavelength. Thus, the found object is either very cold, which pointing to a planet, or a dust shrouded a brown dwarf.
[6] Brown dwarfs intermediate between stars and planets. You do not have enough mass to fuse hydrogen in its interior, but as long as they are young and still pull together, bigger than gas giants like Jupiter.
via Information Wissenschaft
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