# On the Encounter Rate of Open Star Clusters

## TL;DR

This study models the past and future close encounters of open star clusters in the Milky Way, revealing their frequency and potential influence on stellar populations, using orbit integration with the galpy package.

## Contribution

It provides the first detailed estimates of encounter rates of open clusters over 64 million years in the Galaxy using orbit integration.

## Key findings

- Cluster encounters occur at 35-40 events per Myr near the Sun.
- Encounters between clusters of different ages happen at 15 events per Myr.
- Close approaches of cluster pairs are actively occurring, with 29 pairs currently at their closest approach.

## Abstract

Probable past and future close encounters of open clusters with known characteristics over 64 million years have been calculated by integrating the orbits of cluster centers in the Galactic potential using the _galpy_ package. It has been shown that in the Galactic neighborhood of the Sun, pairwise cluster encounters at distances comparable to or smaller than their sizes occur at a characteristic rate of 35 to 40 events per 1 Myr. Close encounters between open clusters with a significant age difference occur at a rate of 15 events per Myr. It can be expected that in the Galaxy as a whole, such events occur an order of magnitude more frequently per unit time. Thus, dynamical interactions between stellar ensembles of different ages may not be too rare and could influence the properties of stellar populations. A pair of clusters with similar ages: HSC 1428 and Gulliver 22 was identified as a likely physically bound binary cluster system. A forecast of expected close encounters over the next 32 Myr has been provided for 490 pairs of clusters. Currently, 29 pairs of clusters are at their closest approach.