Predicting Exoplanet Occurrence Rates

Examining data from TESS and Kepler to inspect exoplanet occurrence rates around main sequence stars.

Abstract

Exoplanets are planets which orbit stars other than the Sun, and over 5000 have now been discovered orbiting a range of star types. Exoplanets can be detected through indirect kinematic, indirect photometric, and direct methods. They predominantly orbit F-, G-, K-, and M-type stars and can be grouped according to size or atmosphere; for example, super Earths, sub-Neptunes, or hot Jupiters. Various hypotheses exist regarding exoplanet formation, and therefore how many of each type of exoplanet exist around each type of star. Precise occurrence rates for specific types of exoplanets are currently unknown, and data regarding relationships between stellar properties, exoplanet formation, and occurrence rates are also missing.

     This review aims to inspect literature concerning exoplanet occurrence rates predominantly around F-, G-, and K-type stars, and consider whether occurrence rates can be predicted. It can be shown that there are links between stellar and exoplanet properties, and that certain start types are more likely to host exoplanets. However, accurate prediction will only be possible when stellar surveys are completed.

     Exoplanets are formed in the galactic environment surrounding stars, utilising the same materials. This leads to changes in the exoplanet’s evolution and links the development of stars with exoplanet occurrence rates. F-, G-, and K-type stars are generally stable with long lifetime which leads to an environment conducive to exoplanet development. Surveys completed by previous or ongoing missions have increased knowledge of the galaxy, but they do not produce complete catalogues, or they generate false positives. As stellar and exoplanet formation are so closely linked, complete catalogues of star systems are required to accurately predict exoplanet evolution.

     Improvements in machine learning and the technology available onboard space-based missions will enhance data collection and analysis, improving the chances of accurately predicting exoplanet occurrence rates.