A nebula brighter than Orion's stays obscure because it hides down south
The Carina Nebula is four times larger than the celebrated Orion Nebula and even brighter. Yet few people in the Northern Hemisphere know it, because it sits deep in the southern sky. Nicolas-Louis de Lacaille first recorded it in January 1752 while observing from the Cape of Good Hope.
Around 8,500 light years away in a spiral arm of the Milky Way, the nebula is a vast nursery of gas and dust crowded with some of the galaxy's heaviest stars. Its clusters span a range of ages: Trumpler 14, about half a million years old, is among the youngest known, while other groups farther out are older, suggesting that star birth has rippled outward in waves and continues today. The James Webb Space Telescope chose one of its star-forming regions, a ridge nicknamed the Cosmic Cliffs, for its first official science images.
Its most famous resident is Eta Carinae, a hypergiant estimated at 100 to 150 times the Sun's mass and about four million times as luminous. Stars this heavy live on the edge, their outpouring of light almost strong enough to overcome their own gravity. In the 1840s Eta Carinae went through a Great Eruption that briefly made it the second-brightest star in the sky and threw off the Homunculus Nebula, a small two-lobed cloud now the brightest object in the sky at mid-infrared wavelengths. The dust from that outburst also dimmed the ultraviolet light flooding the wider nebula, altering its appearance.
The massive stars sculpt everything nearby. Dark knots of gas trail tails pointing directly away from Eta Carinae, and a dense clump called the Defiant Finger is being eaten away by intense radiation and should vanish within 200,000 to a million years. The Hubble telescope celebrated its twentieth anniversary with an image of Mystic Mountain, a pillar three light years tall from which newborn stars fire jets of gas.
One dark patch, silhouetted against the glow, has its own history of names. John Herschel called it an oval vacuity; in 1873 the writer Emma Converse likened its shape to a keyhole, and the name stuck. The Keyhole, about seven light years across, has changed noticeably since it was first seen, possibly because of shifting radiation from Eta Carinae.
Source: Carina Nebula
