NGC 2024 — Diffuse Nebula in Orion

NGC 2024, the Flame Nebula, is a bright emission nebula in Orion immediately east of Alnitak (Zeta Orionis), about 1,400 light-years away. A dark dust lane bisects the nebula vertically, giving it the cleft, flickering appearance that earned its name. Behind the visible front lies an embedded star cluster of more than 800 young stars, only a few hundred thousand years old; ultraviolet radiation from these hot newborns ionizes the surrounding gas and powers the visible glow. The nebula is a major target in star-formation studies because its proximity makes individual protostars accessible to detailed observation.

Despite its catalog brightness, the Flame is a tricky visual target because the brilliant nearby star Alnitak floods the eyepiece with glare. The trick is to position Alnitak just outside the field of view: a 4-inch at moderate power then shows a bright nebulous glow split by a dark lane. An 8-inch at 100-150x with a UHC filter and Alnitak hidden behind the field stop reveals the flame structure clearly. Better than most filters: simply use an occulting bar made from a strip of dark tape. Best observed November through March.

Discovered by William Herschel on 1 January 1786. The embedded cluster's existence was inferred from infrared observations in the 1960s and 1970s, when techniques first allowed astronomers to see through the obscuring dust to count the hidden stars. The Spitzer Space Telescope and later JWST have catalogued individual cluster members and protoplanetary disks.