# Astro2020 Science White Paper: Science at the edges: internal kinematics of globular clusters' external fields

## TL;DR

This paper emphasizes the importance of studying the outer regions of globular clusters to understand their formation, evolution, and their role in galactic dynamics, highlighting WFIRST's potential for such observations.

## Contribution

It advocates for using WFIRST's high-precision proper motion measurements to explore the uncharted outskirts of globular clusters.

## Key findings

- WFIRST can effectively measure proper motions in cluster outskirts.
- Understanding outer regions informs cluster formation and galactic dynamics.
- High-precision data can reveal stellar populations near the hydrogen-burning limit.

## Abstract

The outer regions of globular clusters can enable us to answer many fundamental questions concerning issues ranging from the formation and evolution of clusters and their multiple stellar populations to the study of stars near and beyond the hydrogen-burning limit and to the dynamics of the Milky Way. The outskirts of globular clusters are still uncharted territories observationally. A very efficient way to explore them is through high-precision proper motions of low-mass stars over a large field of view. The Wide Field InfraRed Survey Telescope (WFIRST) combines all these characteristics in a single telescope, making it the best observational tool to uncover the wealth of information contained in the clusters' outermost regions.