A green glow in Orion once convinced astronomers they had found a new element
Look at the middle of Orion's sword and one point seems slightly blurred. That smudge is the Orion Nebula, about 1,267 light-years away and the closest region of massive star formation to Earth. Oddly, neither Ptolemy nor Galileo mentioned it, though both recorded other hazy patches, and Galileo even studied stars nearby.
Credit for recognising its cloudy nature usually goes to the Frenchman Nicolas-Claude Fabri de Peiresc, who viewed it through a refracting telescope on 26 November 1610. Johann Baptist Cysat, a Jesuit in Lucerne, published the first account in 1619, and Christiaan Huygens drew its central region in detail in 1659. Charles Messier logged it on 4 March 1769 as the 42nd entry in his catalogue, which is why it is still called M42.
Photography and spectroscopy transformed the picture. In 1865 William Huggins showed that its light came from glowing gas. On 30 September 1880 Henry Draper exposed a dry photographic plate for 51 minutes, producing history's first photograph of a nebula. Its colours posed a riddle, though. The red comes from hydrogen and the blue-violet from starlight reflected off dust, but early twentieth-century scientists could not match the green to any known spectral line and invented a hypothetical element, nebulium. Later atomic physics revealed the true source: doubly ionised oxygen undergoing a rare, so-called forbidden transition that could not then be reproduced in laboratories.
At the heart lies the Trapezium, a tight cluster named for four bright stars forming a trapezoid, itself part of a larger group of around 2,800 stars. Robert Trumpler named that cluster in 1931. Since the Hubble Space Telescope first turned toward the nebula in 1993, it has spotted protoplanetary disks around most of the newborn stars. A 2005 image took 104 orbits and captured more than 3,000 stars, including infant brown dwarfs.
Newer instruments keep adding surprises. In October 2023 the James Webb Space Telescope revealed pairs of free-floating objects with roughly Jupiter's mass, nicknamed JuMBOs. In July 2025 Webb and the ALMA radio array caught a planet beginning to form around HOPS-315, a young protostar, seen through a rare gap in its surrounding dust.
Source: Orion Nebula
