Unveiling the youngest exoplanet population
Tuesday 3 July, 14:20
Thanks to the exquisite spatial resolution of ALMA, a rich morphology of gaps, rings and spirals is being uncovered in proto-planetary discs. The most compelling explanation for their origin is that they are the signposts of the youngest exoplanets we know of, still in the process of forming. In this hypothesis, I will discuss what are the masses and locations of the planets implied to explain the observed structures. I will highlight in particular how to derive from observation of gaps and rings accurate measurements of the mass of the perturbing planet. The limit on how well we can measure this mass comes from our limited knowledge of the disc conditions (in particular of the disc viscosity), ultimately limiting the precision to a factor of 2-3. Alternative explanations for these structures, not involving planets, have however been invoked. I will discuss a possible way to prove or disprove the planetary origin. While most observations have so far focused on the continuum, I will show how ALMA observations of molecular lines can place constraints on the planet mass independently from the continuum. Two very different values of the planet mass would therefore be at odds with the planetary hypothesis.