Brown dwarfs celebrate their 25th birthday: what have we
learned and what is missing?
A Cool Stars 21 Splinter Session. 22 - 26 June 2020, Toulouse, France

Goal of the Splinter session

*****Cool Stars 21 has been postponed to Spring/early Summer2021 *****

Message from the LOC & SOC: We regret to announce that the Cool Stars, Stellar Systems, and the Sun 21st Conference, originally planned to be held on June 22-26, 2020, in Toulouse, France, has to be postponed due to the current Covid-19 pandemic. The decision was discussed within the SOC and LOC, and agreed by all members of the organizing committees. We plan to reschedule CS21 in Spring/early Summer2021. Please refer to the CS21 website for the latest news:

Brown dwarfs were theoretically proposed independently in the 1960s by Kumar and Hayashi & Nakano. In 1995, two independent teams announced only a few weeks apart the discovery of a young brown dwarf in the Pleiades cluster (Rebolo et al. 1995) and a methane-bearing brown dwarf orbiting Gl229A (Nakajima et al. 1995), both announced at Cool Stars 9. Since then, major scientific breakthroughs have taken place:

  1. Thousands of brown dwarfs have been discovered, including several of the nearest systems to the Sun. The new spectral classes, L, T, and Y, have been defined, each having distinct photometric and spectroscopic properties that extend the brown dwarf sequence to temperatures as low as 250K,
  2. Spectral sub-classes with metallicity and gravity variations have been discovered and defined. Free-floating planetary-mass brown dwarfs down to a few Jupiter masses have been detected,
  3. Large numbers of multiple substellar systems have been resolved and dynamical orbits used to constrain evolutionary models,
  4. A Doppler map of the cloudy photosphere for the nearest brown dwarf binary has been created,
  5. Variability studies have shown that atmospheres of brown dwarfs are highly structured, particularly at the L/T transition,
  6. Brown dwarfs have shown to be radio-emitting sources, potentially driven by auroral-like mechanisms.

Despite this progress, several key scientific questions about substellar objects remain to be addressed with the next generation of space missions and large ground-based telescopes (e.g. ALMA, JWST, Euclid, WFIRST, LSST, E-ELT, TMT). This Splinter session provides an ideal opportunity to build on the knowledge of brown dwarfs gained in the past 25 years and to discuss future opportunities of brown dwarf research with upcoming facilities and state-of-the-art atmospheric and evolutionary models. These include:

  1. Measuring the mass-radius relationship in the brown dwarf and planetary mass regimes
  2. Determining the dominant mechanism(s) for brown dwarf formation and the IMF
  3. Assessing the existence and properties of clouds and their impact on brown dwarf spectra and evolution
  4. Understanding the physical mechanisms responsible for the L/T and T/Y transitions
  5. Observing and modelling pre-substellar cores, proto-brown dwarfs, jets and outflows in brown dwarfs
  6. Investigating the origins of magnetic emission and generation of magnetic fields in these cool, fully convective objects