INPhINIT Incoming PhD: " Understanding how exoplanets are born, how they mature and how they survive the death of their star"

CARMENES consortium and instrument study planetary systems and their stars. We focus on very small stars because of the great interest they present for the discovery of habitable exo-Earths. To this aim, our group built CARMENES, an instrument, the first of its kind worldwide, currently in operation at CAHA observatory, to detect habitable exoplanets.

The closest stellar neighbour to our Sun is Proxima Centauri, a small M dwarf, the most abundant type of stars in our Galaxy and the nearest in distance to our Sun. We know that, according to observations, most of them host planetary systems. To understand them better, we need to accurately determine the parameters and internal structure of the host stars and understand the physical processes behind their variability and the formation and dynamics of planets around them.

Most exciting is to learn about the evolution in time of the whole system. Stars form from enormous clouds of gas and dust. However, we do not know yet if their planets form from the same cloud, once it has collapsed to form a disk orbiting the star, or by coagulation of the dust into larger rocks to form the core of planets. We do not know well where they form within the disk or how they migrate to form the mature, close-in systems that we observe. This is due, mainly, to the fact that there are extremely few detections of protoplanets with the RV technique, which would provide accurate minimum masses and orbital parameters for these objects.

At the other end of the star’s life, we have not detected yet exoplanets around white dwarfs (WDs), the final fate of stars like our Sun. Their detection would probe the evolution of planetary systems during the late stellar evolutionary phases to learn about the fate of our own Solar System. Searches using the classical RV monitoring are hampered by the shape of the light (the spectrum) emitted by these stars. However, material falling onto the WD from an orbiting debris disk produces signatures that make this RV monitoring possible.