Dr. Xavier Haubois

I am a Staff Astronomer at ESO/VLTI with the position of VLTI System Scientist.

My current research focuses on evolved stars: mass loss, pulsation, convection, and dust formation. I use mostly high-resolution techniques and particularly optical interferometry. I am also involved in GRAVITY, a 4-beam optical interferometer operating in K-band.

Evolved stars are stars that are at end of their lives. The way they lose their mass determines when and how they are going to turn into Planetary Nebulae or into Supernovae for the most massive stars. This phenomenon, that also leads to the chemical enrichment of galaxies, is still to be fully understood.

Interferometric reconstructed image of the red supergiant Betelgeuse in H-band (1.65 microns). The two bright spots on the stellar surface are probably an effect due to gigantic convection cells. Assuming a distance of about 200pc, each spot has a diameter equivalent to the distance between the Sun and the Earth. From Haubois et al., 2009.

My appraoch is to observe these objects with a great spatial accuracy. I specialized in using optical interferometry instruments that deliver a spatial resolution of the order of 1-10 milli-arcseconds.This allows me to scrutinize the very surface of these objects and look for symptoms of mass loss. In red supergiants, and also in the less massive AGB stars (Asymptotic Giant Branch), convection is supposed to play an important role in lifting the material above the surface. From there, it condenses into dust that is then carried further away to the ISM (Interstellar Medium) under the action of the stellar radiation. Part of my work is to know how this happens exactly. What are the timescales and the energy involved? How does the material get transferred and transformed in the dust formation zone? These are some of the questions I'm working to answer.