The Great Orion Nebula

Degree of difficulty 1 (of 5)

Minimum aperture Naked eye

Designation NGC 1976

Type Galactic nebula

Class Emission and reflection nebula

Distance 1300 ly (K2005) 1470 ly (2003), 1530 ly (2001)

Size 35 ly

Constellation Orion

R.A. 5h 35.3min

Decl. –5° 23′

Magnitude 3.7

Surface brightness 20mag/arcsec2

Apparent diameter 90′×60′

Discoverer Peiresc, 1611

History M 42, the Great Orion Nebula, was not known to the pre-telescopic observers. Neither do we find hints in the documents of antiquity that would suggest sightings of this nebula with the naked eye. Rather, both Ptolemy and Tycho cataloged, at the position of M 42, a star: θ Orionis.

The Frenchman Nicholas-Claude Fabri de Peiresc was the first to mention this nebula in 1611. By 1609, Galileo Galilei had made a sketch of that star field with his telescope. He counted 80 stars but, mysteriously, did not recognize M 42. However, an independent discovery was made in 1611 by Johann Baptist Cysatus.

The first of a large number of historic drawings of this nebula was made by Giovanni Batista Hodierna in 1654. Two years later, Christian Huygens observed M 42 and described the view with the words: “In the sword of Orion, three stars are rather close to each other. In 1656, when I observed the one of them in the middle with my telescope, twelve stars appeared. Three of them nearly touched each other [the Trapezium] and, together with four other, were shining through a nebula, so that the space around them was brighter than the rest of the sky, which was perfectly clear and dark; it formed the effect of an opening in the sky, through which a brighter region became visible.”

Following this first mention of the Trapezium, the fourth Trapezium star was discovered in 1673 by Picard, and confirmed by Huygens in 1684.