Editing Pleiades (section)

== Observational history ==
[[Galileo Galilei]] was the first [[astronomer]] to view the Pleiades through a [[telescope]].<ref>{{Cite web |title=Messier 45 (The Pleiades) |url=https://science.nasa.gov/mission/hubble/science/explore-the-night-sky/hubble-messier-catalog/messier-45/ |url-status=live |archive-url=https://web.archive.org/web/20231116112505/https://science.nasa.gov/mission/hubble/science/explore-the-night-sky/hubble-messier-catalog/messier-45/ |archive-date=November 16, 2023 |access-date=November 16, 2023 |website=NASA Science |language=en}}</ref> He thereby discovered that the cluster contains many stars too dim to be seen with the naked eye. He published his observations, including a sketch of the Pleiades showing 36 stars, in his treatise ''[[Sidereus Nuncius]]'' in March 1610.

The Pleiades have long been known to be a physically related group of stars rather than any chance alignment. [[John Michell]] calculated in 1767 that the probability of a chance alignment of so many bright stars was only 1 in 500,000, and so surmised that the Pleiades and many other clusters must consist of physically related stars.<ref>
{{cite journal
 |author=Michell J.
 |date=1767
 |title=An Inquiry into the probable Parallax, and Magnitude, of the Fixed Stars, from the Quantity of Light which they afford us, and the particular Circumstances of their Situation
 |journal=[[Philosophical Transactions]]
 |volume=57 |pages=234–264
 |doi=10.1098/rstl.1767.0028
|bibcode=1767RSPT...57..234M
|doi-access=free
 }}</ref> When studies were first made of the [[proper motion]]s of the stars, it was found that they are all moving in the same direction across the sky, at the same rate, further demonstrating that they were related.

[[Charles Messier]] measured the position of the cluster and included it as "M45" in his [[Messier object|catalogue]] of [[comet]]-like objects, published in 1771. Along with the [[Orion Nebula]] and the [[Beehive Cluster|Praesepe]] cluster, Messier's inclusion of the Pleiades has been noted as curious, as most of Messier's objects were much fainter and more easily confused with comets—something that seems scarcely possible for the Pleiades. One possibility is that Messier simply wanted to have a larger catalogue than his scientific rival [[Nicolas-Louis de Lacaille|Lacaille]], whose 1755 catalogue contained 42 objects, and so he added some bright, well-known objects to boost the number on his list.<ref>
{{cite web
 |author=Frommert, Hartmut
 |date=1998
 |title=Messier Questions & Answers
 |url=http://messier.seds.org/m-q&a.html#why_M42-45
 |access-date=2005-03-01
}}</ref>

[[Edme-Sébastien Jeaurat]] then drew in 1782 a map of 64 stars of the Pleiades from his observations in 1779, which he published in 1786.<ref>A New review: with literary curiosities and literary intelligence, page 326, [[Paul Henry Maty]], Printed for the author, 1783.</ref><ref>Mémoires de [[French Academy of Sciences|l'Acadêmie des sciences de l'Institut de France]], page 289, Didot frères, fils et cie, 1786.</ref><ref>Edme-Sébastien Jeaurat, ''Carte des 64 Principales Etoiles des Playades par M. Jeaurat, pour le 1.er Janvier 1786''.</ref>