“Extrasolar Planets and Brown Dwarfs”

REPORT ON THE FIRST ADVANCED CHILEAN SCHOOL ON ASTROPHYSICS “EXTRASOLAR PLANETS AND BROWN DWARFS”

DANIELLE ALLOIN (ESO) AND DANTE MINNITIINNITI (PUC)

RGANIZED by D.Minniti To-do list: increase the sample (PUC), D.Alloin (ESO), of brown dwarfs, to test mod- MT.Ruiz (UChile), els, make a proper motion sur- G.Pietrzynski (UCon- vey in the NIR, formation sce- cepcion), and sponsored nario: ascertain the low mass ObyO the FONDAP Center for Astrophysics, end of the stellar IMF, the rela- European Southern Observatory, Princeton/ tion planets = brown dwarfs? Catolica Universities, Fundacion Andes, SOCHIAS, and NRAO, the goal of this • Extrasolar planets: series of Schools (http://www.astro.puc.cl/ Michel Mayor and other con- ~school/) is to train the young generation of tributors reported that it is as astronomers on different topics. The School well a “tough job” to find plan- format has been chosen in order to allow a ets (light contrast star/planet deep approach of the selected themes, as around 1010, request for 1 m/s well as to maximize exchanges between the velocity precision). Radial invited lecturers and the attendees. velocity searches have so far tremendous increase in computational For this School on Extrasolar Planets provided all known planets (~120), except power). and Brown Dwarfs, held in Santiago on 15- for one. About 2000 stars in the solar vicini- To-do list: improve the opacities, consider 19 December 2003, the four main lecturers ty are currently monitored (at distances less more realistic dust grains (composition, were (see photo): Jill Knapp (UPrinceton), than 30 pc). Among the 120 known planets, shape) Michel Mayor (UGenève), France Allard 10 are multiple planet systems. (ENS Lyon), and Scott Tremaine The use of other methods for planet dis- • Dynamics, kinematics, formation sce- (UPrinceton). covery, such as transit, reflected light, micro- narii: a large panel of fascinating problems Since the mid-90s, the field of brown lensing, etc... is in progress. were discussed by Scott Tremaine and other dwarfs and extrasolar planets has bloomed in To-do list: understand the amazing depend- contributors at the School.. a spectacular fashion, both on the observa- ence on the metallicity of the parent star, To-do list (a subset...): elucidate the “mys- tional side and on the modeling side. Rather investigate the brown dwarf desert and tery” of the planetesimal growth from cm than report on all the advances beautifully investigate its implications on the formation size to km size, understand the physics hid- presented at the School, let us examine some scenarii, increase the sample of known plan- den in the term “viscosity” in protoplanetary of the points which remain in the to-do lists ets up to 104, so that statistical properties can discs, understand the “peculiarities” of the shown by the different lecturers. be derived with some confidence: at the cur- Solar system: its ellipticity, the location of First of all, we shall stick, for the time rent rate of planet discovery (about 10/year), Jupiter, the origin of chondrules, formation being, to the definition adopted by the IAU: this will take 103 years!! Can we wait that scenarii: collapse versus coagulation of plan- long? etesimals. • “star”: mass above 80 MJup, H-burning core • “brown dwarf”: mass between 80 and It was also extremely interesting to hear • Some other interesting questions con- about intrinsic limitations in planet searches: cerning the modeling of planetary systems 13 MJup, D burning core, large variation of the surface temperature from an M dwarf accoustic modes of the parent stars, spots of were raised: are closed-box models valid? (3,000 K), to a T dwarf(< 1,300 K) the parent stars, and in the case of multiple Given that half the mass of the Solar system planet systems, the difficulty in finding a is in small bodies, taking into account only • “planet”: mass less than 13 MJup One notices that this definition is not unique solution in the decomposition of the massive planets to study the dynamics of linked to the object formation scenario. radial velocity curve. planetary systems might be misleading; how The number of objects known so far are: to disentangle evolution (such as planet about 120 planets (at distances up to 30 pc) • Of course, a wealth of groundbased migration) from intrinsic properties?; what is and about 400 brown dwarfs (at distances up and space tools for discovering planets and the role of star multiplicity in the formation to 200 pc). brown dwarfs were discussed (incomplete of planetary systems?; which is the fraction list!): HARPS (1m/s precision), optical and of lost planets? On the front of observing: NIR interferometry, adaptive optics -in the • Brown dwarfs: Jill Knapp and other future multi-conjugate adaptive optics, In conclusion, an enlightening School, contributors at the School reported that it is COROT, KEPLER, ALMA for protoplane- which took place in the grounds of the a “tough job” to find them (intrinsic lumi- tary discs, SIM, GAIA, GEST, OWL and Observatory of Cerro Calan in the heights of nosity less than 2·10−6 solar luminosity and ELTs in general. Santiago. About 80 attendees (more than (V-K) ~ 10). Exploiting the all-sky surveys half of them from South America) enjoyed available today, more than one million On the front of modeling: the lectures, the discussions in the shadow of objects have been searched for: only 60 L • The atmospheres of brown dwarfs the trees, and contributed to the friendly dwarfs have been found... Good progress were extensively discussed by France atmosphere. Finally, the School dinner at has been made in the M/L/T brown dwarf Allard. They are rather well understood and Casa Piedra allowed everyone to admire a classification (on the basis of their spectra). modeled (thanks, among other factors, to the beautiful sunset on the rio Mapocho.