Preferred Hosts for Short-Period Exoplanets
In an effort to learn more about how planets form around their host stars, a team of scientists has analyzed the population of Kepler-discovered exoplanet candidates, looking for trends in where they’re found.
Since its launch in 2009, Kepler has found thousands of candidate exoplanets around a variety of star types. Especially intriguing is the large population of “super-Earths” and “mini-Neptunes” — planets with masses between that of Earth and Neptune — that have short orbital periods. How did they come to exist so close to their host star? Did they form in situ, or migrate inwards, or some combination of both processes?
To constrain these formation mechanisms, a team of scientists led by Gijs Mulders (University of Arizona and NASA’s NExSS coalition) analyzed the population of Kepler planet candidates that have orbital periods between 2 and 50 days.
Mulders and collaborators used statistical reconstructions to find the average number of planets, within this orbital range, around each star in the Kepler field. They then determined how this planet occurrence rate changed for different spectral types — and therefore the masses — of the host stars: do low-mass M-dwarf stars host more or fewer planets than higher-mass, main-sequence F, G, or K stars?