Denys Wilkinson Building, Department of Physics, University of Oxford, Keble Road, Oxford OX1 3RH
Andrew Collier Cameron (St Andrews)
Lawrence Clark - Lawrence.selmons-clark@physics.ox.ac.uk
The Sun as a star seen through planet-hunting instruments
Despite spectacular advances in the stability and precision of radial-velocity
spectrometers over the last 3 decades, the detection threshold for the reflex orbital
motion of planet-host stars has been stalled at around 1 m/s for the last 15 years.
This is an order of magnitude greater than is needed for determining the masses
of Earth analogues around solar-type stars. The culprit is stellar activity, whose
forms range from p-modes and photospheric granulation to Doppler-shifted flux
perturbations by dark spots and bright faculae, to localised magnetic suppression of
convective flows at different depths in the photosphere.
A small, purpose-built solar telescope has been feeding integrated sunlight into
the HARPS-N radial-velocity spectrometer every clear day since July 2015. I will review a
selection of the ongoing investigations that are using these Sun-as-a-star data to
develop both data-driven and physics-based methods for separating the effects of
stellar photospheric physics from true dynamical Doppler shifts.