Microlensing Searches for Planets: Results and Future Prospects

TL;DR

Microlensing is a promising method for detecting a wide range of exoplanets, including free-floating planets, with recent results and future prospects indicating its potential for comprehensive planetary census.

Contribution

This paper reviews the current state of microlensing planet searches, summarizes recent detections, and discusses future experiments and their expected impact on exoplanet demographics.

Findings

Four planets detected via microlensing.

Microlensing provides insights into planet frequency beyond the snow line.

Next-generation surveys could complete a census of planets larger than Mars.

Abstract

Microlensing is potentially sensitive to multiple-planet systems containing analogs of all the solar system planets except Mercury, as well as to free floating planets. I review the landscape of microlensing planet searches, beginning with an outline of the method itself, and continuing with an overview of the results that have been obtained to date. Four planets have been detected with microlensing. I discuss what these detections have taught us about the frequency of terrestrial and giant planets with separations beyond the ``snow line.'' I then discuss the near and long-term prospects for microlensing planet searches, and in particular speculate on the expected returns of next-generation microlensing experiments both from the ground and from space. When combined with the results from other complementary surveys, next generation microlensing surveys can yield an accurate and complete census of the frequency and properties of essentially all planets with masses greater than that of Mars.