# Ground-based Microlensing Surveys

## TL;DR

Microlensing is a powerful method for detecting diverse exoplanets, especially cool, low-mass, and free-floating planets, offering unique insights into planet formation and complementing other detection techniques.

## Contribution

This paper advocates for an expanded, well-funded microlensing survey component in future exoplanet research to achieve a comprehensive understanding of planetary populations.

## Key findings

- Microlensing has already discovered four exoplanets.
- It is sensitive to planets inaccessible by other methods.
- Next-generation surveys can provide a complete planetary census.

## Abstract

Microlensing is a proven extrasolar planet search method that has already yielded the detection of four exoplanets. These detections have changed our understanding of planet formation ``beyond the snowline'' by demonstrating that Neptune-mass planets with separations of several AU are common. Microlensing is sensitive to planets that are generally inaccessible to other methods, in particular cool planets at or beyond the snowline, very low-mass (i.e. terrestrial) planets, planets orbiting low-mass stars, free-floating planets, and even planets in external galaxies. Such planets can provide critical constraints on models of planet formation, and therefore the next generation of extrasolar planet searches should include an aggressive and well-funded microlensing component. 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 planets, and in particular low-mass terrestrial planets.