NANESSE, a nanosatellite for asteroseismology of Alpha Cen

Alpha Centauri is the third brightest star in the night sky and the closest stellar system to us. It is composed of two stars similar to the Sun, Alpha Cen A and B, and a more distant, red dwarf star, Proxima. Alpha Cen A and B masses enclose that of the Sun, and both present stellar pulsations. Their interpretation -a science known as asteroseismology- delivers us important constraints on the internal structure (presence/absence of a convective core) as well as stringent constraints on the age of the system. Alpha Cen is thus an essential testbed for a better understanding of stellar evolution of solar analogues. The recent announcement of a possible exoplanet orbiting the B component reinforces its interest. Paradoxically the brightness of the system hampers specific investigation with the large ground- and space-based telescopes, its investigation ideally requiring a dedicated instrument.

With the progress in the small satellite technologies, we have conceived the NANESSE project, a satellite of the nano class (1-10 kg) that would perform a high-precision photometric survey of Alpha Cen. We have identified three options allowing for the asteroseismic characterisation of the system, and confirmation of its hypothetical exoplanet(s), at different levels of accuracy depending of the design eventually adopted. In this talk, we first present the science objectives and specifications of the mission. We then describe the different instrumental designs we envision onboard the nanosatellite.