M45

M45, better known as the Pleiades cluster, is a well-known star to astrophotographers. It is an open cluster of stars that can be observed from both the northern and southern hemispheres thanks to its position in the Taurus constellation.

According to Professor Wolfhard Schlosser, this open cluster was already very important in the Neolithic period because its appearance in the northern hemisphere corresponded to the beginning of the harvest. M45 was also very useful in antiquity in order to create calendars for two reasons: its very visible and easily recognizable appearance as well as its position which marks the vernal point, that is to say the place where the celestial equator and the ecliptic intersect. Thus, M45 was known all around the globe since Antiquity.

M45 is thus closely linked to Greek and Mesopotamian mythology. In ancient Greece, the Pleiades are seven sisters, daughters of Atlas and Pleione: Asterope, Merope, Electra, Maia, Taygete, Celaeno and Alcyone. According to Eratosthenes, most of them were united with gods, giving birth to various royal families such as those of Troy or Sparta. The Pleiades are even mentioned in Homer's "Odyssey" (song V) as well as in the Bible.

In astronomy, an open cluster is necessarily young in contrast to denser globular clusters and therefore capable of maintaining coherence over long periods of time. The Pleiades are less than 100 million years old and will have dispersed in about 250 million years due to gravitational interactions and lack of density. The cluster extends over 86 light years.

Astrophotography reveals large clouds of dust around some stars that take on a blue tint because of them. Indeed, the brightest are also the youngest and are very hot blue supergiants of type B. However, this dust is not the remains of the nebula that allowed the formation of these stars thanks to the contraction of a large cloud of gas. Studies carried out on M45 have shown that the cluster is currently crossing a cloud of interstellar dust and that it is indeed this which appears on the images. The remains of the original cloud having been swept away and dispersed by the very strong radiation of the blue supergiants.

Equipment used:
- Zwo AM5
- Asiair plus
- 533mc pro
- 120mm mini (with optical divider)
- EAF
- Filter wheel
- Stacked with Siril
- Processed with PixInsight
- Finished with Lightroom