Gaia Shows That Messier 40 is Definitely Not a Binary Star

TL;DR

Using Gaia and Hipparcos data, this study conclusively shows that Messier 40 is not a binary star but a pair of unrelated stars, clarifying its nature in the Messier Catalogue.

Contribution

The paper provides the first definitive evidence that Messier 40 is not a physical binary, resolving longstanding doubts with precise astrometric data.

Findings

Gaia and Hipparcos parallaxes show the stars are unrelated.

Messier 40 is not a gravitationally bound binary system.

Clarifies the nature of Messier 40 in astronomical catalogs.

Abstract

M40 has always been something of an oddity in the Messier Catalogue, since it is just a pair of stars rather than an extended object. Doubts have also been expressed as to whether it is even a physical binary. Here, we note that the Hipparcos/Gaia parallaxes for these two stars remove all doubt: Messier 40 comprises a pair of entirely unrelated stars.