A day spent at home due to a severe cold, I took the opportunity to elaborate last year's shots on the Pleiades M45.
The Pleiades (also known as the Seven Sisters, the Chioccetta or with the initials M45 in the catalog of Charles Messier) are an open cluster visible in the constellation of Taurus. This cluster, quite close (440 light years), has several stars visible to the naked eye; even if only four or five of the brightest stars are visible from city environments, twelve can already be counted from a darker place. All its components are surrounded by light reflection nebulae, especially observable in long exposure photographs taken with large telescopes.
Remarkable is that the stars of the Pleiades are really close to each other, have a common origin and are linked by gravity.
Given their distance, the stars visible between the Pleiades are much hotter than normal, and this is reflected in their color: they are blue or white giants; the cluster actually has hundreds of other stars, most of which are too distant and cold to be visible to the naked eye. The Pleiades are in fact a young cluster, with an estimated age of about 100 million years, and an expected life of only another 250 million years, as the stars are too far apart.
Because of their brilliance and proximity to each other, the brightest stars of the Pleiades have been known from antiquity: they have already been mentioned for example by Homer and Ptolemy. The Disc of Nebra, a bronze artifact from 1600 BC. found in the summer of 1999 in Nebra, Germany, it is one of the oldest known representations of the cosmos: in this disc the Pleiades are the third clearly distinguishable celestial object after the Sun and the Moon.
Since it was discovered that the stars are celestial bodies similar to the Sun, it was started to hypothesize that some stars were in some way related to each other; thanks to the study of proper motion and the scientific determination of the distances of the celestial bodies, it became clear that the Pleiades are really gravitationally bound and that they even have a common origin.