Topic: Cool Stars as Exoplanet Hosts
Stellar activity even at low level produced by spots and plages affects the radial velocity signatures. It is therefore crucial to determine how it influences our ability to detect small planetary signals such as those produced by Earth-mass planets in the habitable zone. We focused on the solar case: thanks to the wealth of accurate data available, the Sun gives us a unique opportunity to test the impact of stellar activity on such detections. We use then the Sun as a template and we investigate in detail the impact of spots and plages as well as the role played by the attenuation of convection due to the presence of magnetic activity. We will present the detection limits obtained in various conditions (either solar or with different activity levels). We find that the plage contribution due to the convective blueshift attenuation dominates the total signal, with an amplitude over the solar cycle of about 8-10 m/s, and show that such a signal prevents the detection of the Earth around the Sun even with forthcoming high precision RV instruments, unless ways to correct the signal are found. We therefore propose practical ways to correct for the activity on various timescales from days to years, and use again the Sun to estimate the ultimate detection limits achievable once the signal is corrected from the Sun's activity. These detection limits will be presented and discussed.