The best proto-brown dwarf candidate so far: PR from Calar Alto

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Brown dwarfs are sometimes called “failed stars”. They are born from interstellar clouds following processes closely related to the formation of normal stars. But brown dwarfs lack mass enough to light up nuclear reactions in their interiors. Thus, they cannot be considered true stars and in fact some properties reassemble those shown by giant planets. Uncovering proto-brown dwarfs, i.e., brown dwarfs in their very first evolutionary stages, is a long-sought hit. A recent study has found the best proto-brown dwarf candidate known to date. Calar Alto has contributed key data to this finding…

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The first brown dwarfs were discovered in 1995. A lot has been learned about them since that date, but the formation mechanism (or mechanisms) is a hotly debated issue. The processes leading to the birth of a brown dwarf are, no doubt, related to those forming normal stars, but many details are lacking. Stars and brown dwarfs evolve very rapidly during their first stages, what makes quite difficult to catch them in the very process of birth. This challenge is even more difficult due to the fact that extremely young objects are still embedded into the gas and dust clouds from which they condense. This is the “Class 0/I stage”, in the classical evolutionary scheme of young stellar objects.

A recent international study leaded by David Barrado y Navascués (LAEX-CAB, INTA-CSIC) has identified the best proto-brown dwarf candidate known to date. Their search begun analysing data obtained with the Spitzer infra-red space telescope. They were looking for low-luminosity bodies (dimmer than one tenth of the solar energy output) still embedded within dense nebular cores. A preliminary list of candidates resulted from this search. As stated by Barrado y Navascués, “we acknowledge the fact that we are exploring uncharted water, and that the contamination by extragalactic sources and very extincted stars can mimic the properties of a potential sub-stellar object”. For this reason they “carried out an exhaustive follow-up at different spectral ranges”.

The multi-band analysis was carried out retrieving data from public data bases and, also, making new observations at different observatories. Spitzer, 2MASS and CFHT archive data were used, and observing campaigns were performed with the IRAM 30m radiotelescope (Granada, Spain), ESO’s Very Large Telescope (Chile), Caltech Submillimetre Observatory (Hawaii, USA), Very Large Array (New Mexico, USA) and Calar Alto Observatory (Almería, Spain). Calar Alto data were obtained in 2007 with the Zeiss 3.5 m telescope equipped with Omega 2000 infrared camera. According to the researchers “CAHA data were key to confirm the nature of the object”, by providing near-infrared high spatial resolution imaging, that turned out to be the best proto-brown dwarf candidate yet known.

This object, known as SSTB213 J041757, is placed in Taurus constellation, inside the dark cloud Barnard 213, at a distance of 450 light-years (140 parsecs). CAHA imaging has shown that it is a double object, with both components being compatible with the status of Class I proto-brown dwarfs.

Some conclusions can be drawn from this work. In relation to the formation mechanism, the researchers state that “if the source is really associated with a proto-brown dwarf, our observations strongly suggest that it was not formed through the ejection scenario, but rather in a similar way to low-mass stars”.

More observations and work will be needed to find more proto-brown dwarf candidates, and to definitely clarify the nature of these first examples. No doubt this research team will offer new and exciting results in this field, in a near future.

The research described in this press-release was accepted for publication by Astronomy and Astrophysics journal in September 2009. The paper is signed by D. Barrado y Navascués, M. Morales-Calderón, Aina Palau, A. Bayo (all them from LAEX-CAB, INTA-CSIC), I. de Gregorio-Monsalvo (ESO), C. Eiroa (UAM), N. Huélamo (LAEX-CAB, INTA-CSIC), H. Bouy (IAC), Ó. Morata (Academia Sinica & NTNU), and L. Schmidtoreick (ESO).
See Calar Alto Press release and the images here (in English, Spanish and German)


About dbarrado

Born in Madrid, Spain, David Barrado completed a degree in physics, specializing in astrophysics, at the Universidad Complutense de Madrid. At this same university he started work on a doctorate that he would go on to complete at the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge (USA). He then spent several years as a post-doctoral researcher at a number of institutes in the United States (including as a Fulbright scholar during his time at CfA), Germany (Max-Planck Institut für Astronomie, in Heidelberg) and Spain (Universidad Autónoma de Madrid). David now works at the European Space Astronomy Center (ESAC, Madrid) as a member of the National Technical Aerospace Institute (INTA), part of the Astrobiology Center (CAB), a combined institute made up of INTA and the Center for Higher Scientific Research (CSIC). With the INTA team he led research on the MIRI, an infrared instrument that will fly with the forthcoming space telescope, the JWST. He has also been involved in the development of a number of other astronomical instruments. For two years he was head of the Stellar and Exoplanets Astrophysics Laboratory, as a member of the CAB, and later Director of the Hispano-German Astronomy Center observatory in Calar Alto for three years. His research interests focus on the properties of stars in open star clusters, as well as detecting and characterizing substellar objects and exoplanets. More generally he has specialized in studying the formation of stars and planetary systems using various observational techniques: from visible light to distant infrared, using images and spectroscopes, via both terrestrial and space telescopes. This observation work has seen him publish close to one hundred and fifty articles in prestigious scientific journals. He also combines his research with tireless outreach activities. With Spanish blog, Cuaderno de Bitacora Estelar (see http://www.madrimasd.org/blogs/astrofisica/) has a very large audience.

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