Pleiades
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The Pleiades, also known as the Seven Sisters, Messier 45, and other names by different cultures, is an asterism and an open star cluster containing middle-aged, hot B-type stars in the north-west of the constellation Taurus. At a distance of about 444 light-years, it is among the nearest star clusters to Earth. It is the nearest Messier object to Earth, and is the most obvious cluster to the naked eye in the night sky. It is also observed to house the reflection nebula NGC 1432, an HII region.
A color-composite image of the Pleiades from the Digitized Sky Survey
The Nebra sky disc, dated circa 1600 BC. The cluster of seven dots in the upper right portion of the disk is believed to be the Pleiades.
1-dollar commemorative silver coin issued in 2020 by the Royal Australian Mint. On the reverse, the Seven Sisters (Pleiades) are represented, according to an ancient story of Australian Indigenous tradition.
Hubble Space Telescope image of reflection nebulosity near Merope (IC 349)
Messier object
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The Messier objects are a set of 110 astronomical objects catalogued by the French astronomer Charles Messier in his Catalogue des Nébuleuses et des Amas d'Étoiles.
Because Messier was interested only in finding comets, he created a list of those non-comet objects that frustrated his hunt for them. This list, which Messier created in collaboration with his assistant Pierre Méchain, is now known as the Messier catalogue. The Messier catalogue is one of the most famous lists of astronomical objects, and many objects on the list are still referenced by their Messier numbers.
The catalogue includes most of the astronomical deep-sky objects that can be easily observed from Earth's Northern Hemisphere; many Messier objects are popular targets for amateur astronomers.
All Messier objects
Charles Messier
Image: Crab Nebula
Image: Messier 2 HST Potw 1913a