Probing Formation from Stars to Planets: Accretion, Binarity and Disks in Young Brown Dwarfs

Lead Research Organisation: Imperial College London
Department Name: Dept of Physics


The discovery of extrasolar planets over the last decade and a half ranks among the most important advances in the history of astronomy. More than three hundred have been found so far, in a plethora of stellar system architectures, and down to a few Earth masses. Determining the formation mechanism, properties and habitability of these planets (and those of lower mass bound to be detected in coming years) is at the cutting edge of current astrophysical research. These questions are in turn intimately linked to the fundamental issue of star formation, since planets form out of the accretion disks that are an integral outcome of the star-formation process and that ultimately determine the final stellar mass. Finally, the formation and properties of both stars and planets are closely tied to those of brown dwarfs: substellar bodies that straddle the mass range between stars and planets and share many features with both. In this project, I investigate the inter-linked origins of stars, brown dwarfs and planets by addressing 3 broad questions: 1) How do young stars and brown dwarfs accrete material from their surrounding accretion disks? 2) How do brown dwarfs form? 3) Can planets form around brown dwarfs? The research entails a variety of observational techniques, from high-resolution spectroscopy and spectropolarimetry to resolved imaging with adaptive optics, deployed over wavelengths ranging from the optical to sub-millimetre and using both ground- and space-based facilities, allied with theoretical analysis and numerical modeling. The results of the project should provide a broad and comprehensive picture of the physical processes that underlie the formation of objects all the way from from stellar down to planetary masses.


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Dib S (2011) Star formation efficiency as a function of metallicity: from star clusters to galaxies in Monthly Notices of the Royal Astronomical Society

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Kaltenegger L (2011) MODEL SPECTRA OF THE FIRST POTENTIALLY HABITABLE SUPER-EARTH-Gl581d in The Astrophysical Journal

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Mohanty,S., Greaves,J., Mortlock,D., Scholz,A., Apai,D., Lodato,G., Pascucci,I., Looper,D. (2011) Protoplanetary Disk Masses from Stars to Brown Dwarfs - A Bayesian Analysis in Astrophysical Journal, submitted

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Reiners,A., Mohanty,S. (2011) Radius Dependent Angular Momentum Evolution in Low Mass Stars in Science, submitted

Description all outcomes related to this grant have been submitted within the outcomes of our Consolidated Grant ST/K001051/1
Exploitation Route all outcomes related to this grant have been submitted within the outcomes of our Consolidated Grant ST/K001051/1
Sectors Other

Description Habitability of Extrasolar Planets 
Organisation Harvard University
Department Harvard-Smithsonian Center for Astrophysics
Country United States of America 
Sector Academic/University 
PI Contribution I provide the stellar irradiation on the planet, which is crucial for the ultimate chemical processes in the planetary atmosphere and surface and thus habitability
Collaborator Contribution Exploring the Habitability of Extrasolar Planets: collaborator provides the planetary atmospheric models while i provide the stellar irradiation, which together determine the habitability, using simulations run on collaborator's computing facilities.
Impact 1 paper published (see Kaltenegger,L. et al., ApJ, 2011 in publications); 2 more in preparation.
Start Year 2010
Description Protoplanetary Disk MRI 
Organisation Ludwig Maximilian University of Munich (LMU Munich)
Department Astronomy and Astrophysics
Country Germany, Federal Republic of 
Sector Academic/University 
PI Contribution Magnetohydrodynamic processes in protoplanetary disks, to analyse the magnetically-driven accretion processes; combined with the x-ray driven ionization supplied by collaborator's analysis, this determines global disk accretion processes
Collaborator Contribution World-leading code to analyse X-ray interactions with gas and dust in disks
Impact 1 paper submitted to ApJ (see Mohanty,S., Ercolano,B, Turner,N., ApJ submitted, 2011); 1 more in preparation
Start Year 2010
Description Protoplanetary Disk Masses 
Organisation University of St Andrews
Department School of Physics and Astronomy
Country United Kingdom of Great Britain & Northern Ireland (UK) 
Sector Academic/University 
PI Contribution Expertise in protoplanetary disk properties, and in Bayesian statistical analysis
Collaborator Contribution Expertise in sub-mm observing, and in dust properties of protoplanetary disks
Impact Awarded time for first-light pilot observations on SCUBA-2/JCMT; observations complete and resulting paper just submitted to the Astrophysical Journal (see Mohanty, Greaves et al., ApJ, submitted, 2011). We are continuing the collaboration by applying for first-light ALMA observations to extend our results (ALMA Letter of Intent submitted).
Start Year 2010