Around November 25, 1610, French astronomer and savant Nicolas-Claude Fabri de Peiresc discovers the Orion Nebula, a diffuse nebula situated south of Orion’s Belt in the constellation of Orion. It is one of the brightest nebulae, and is visible to the naked eye in the night sky.
Nicolas-Claude Fabri de Peiresc studied at the Jesuit College at Tournon, where he first gained his interest in astronomy, as well as archeology and law. Peiresc came to travel around Europe with his patron Guillaume du Vair, a French author and lawyer. In 1610, du Vair bought a refracting telescope which Peiresc was able to use to observe the skies, especially the Jupiter moons. Probably in the same year, Peiresc discovered the Orion Nebula. 
The Orion Nebula is a luminous cloud of gas, which is visible to the naked eye. However, the brightest stars within the nebula were noted early and cataloged as one bright star of about fifth magnitude: In about 130 AD, Ptolemy included it in his catalog, as did Tycho Brahe in the late 16th century, and Johann Bayer in 1603 – the latter cataloging it as Theta Orion in his Uranometria. In 1610, Galileo detected a number of faint stars when first looking at this region with his telescope, but didn’t note the nebula. Some years later, on February 4, 1617, Galileo took a closer look at the main star, Theta1, and found it to be triple, at his magnification of 27 or 28x, again not perceiving the nebula.
After observing the nebula for the first time, Peiresc referred to it as a cloudy nebulosity.  Modern astronomers found out that the famous nebula lies approximately 1,300 light-years from Earth and at 30 to 40 light-years in diameter, it is probably giving birth to numerous stars. It has been found that an open star cluster, whose stars were born at the same time from a portion of the nebula can be seen in between the nebula. It has also been suggested that there may be a black hole in the cluster as well. 
But, coming back to its discoverer Peiresc, he was not the only one, who noticed the nebula in the night sky. It is assumed that the first published work regarding the nebula appeared in 1619 and was written by Johann Baptist Cysat of Lucerne. Also, the nebula was independently discovered by Christiaan Huygens in 1656, who published his findings in 1659. Charles Messier later categorized the Orion Nebula as M42 in his catalog of deep sky objects. 
At yovisto, you may be interested in a video documentary on the famous Orion Nebula.
References and Further Reading:
-  Biography of Nicolas-Claude de Peiresc
-  The Orion Nebula at Night Sky Info
-  The Orion Nebula at Earth Sky
-  Messier M42
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