Institute of Astronomy

The Demographics of Exoplanets Orbiting Main-Sequence Stars: Recent Results, Challenges and Future Prospects

SpeakerTalk DateTalk Series
Suzanne Aigrain29 July 2014Across HR 2014 Talks


The past few years have seem something of an explosion in the rate of discovery exoplanet around main-sequence stars, driven in large part by the Kepler transit-search mission, but also by a steady improvement in the sensitivity of radial velocity, microlensing, direct imaging and ground-based transit surveys. These larger samples, together with careful evaluation of observational biases, allow for an increasingly detailed investigation of the demographics of the exoplanet population, over a wide range of host star spectral type (A to M) and planet types (Jupiters to Earths). The first order result is that planets are very common: the average number of planets per star (integrated across the full parameter space accessible to current studies) ranges from ~25% (for Sun-like stars) to 50% or more (for M-stars). Small planets (R<2.5 R_earth, M<10 M_earth) in short-period orbits (a<0.5 AU) make up the bulk of this population, and tend to be found in compact, multi-planet systems. Several recent studies have estimated eta_earth -- the frequency of Earth-size planets in the habitable zone of their host star -- though for Sun-like stars this still involves extrapolation.

I will give an overview of recent population studies based on Kepler and other datasets, highlighting the most important trends, discussing the main methodological differences and challenges along the way. I will also compare the results of different surveys to each other and discuss, in very broad terms, their implications for planet formation and evolution models. Finally, I will highlight areas of parameter space where we may expect interesting developments over the next few years.