NGC 2024

Alnitak (Zeta Orionis) and NGC 2024 (The Flame Nebula)
NGC 2024: 1300 to 1600 Light Years
Alnitak: 815 Light Years

Right Ascension: 05 : 41.9 (hours : minutes)
Declination: -01 : 51 (degrees : minutes)

Although the bright light of Alnitak (Zeta Orionis) dominates the image and threatens to overwhelm the flame-like nebula, the two are not physically related. NGC 2024 is an HII region forming a blister on the surface of the Orion B molecular cloud complex which resides 1500 light years away. Alnitak on the other hand is several hundred light years in the foreground at a distance of 815 light years.

The Flame Nebula's bifurcated dusty structure is mostly opaque to optical telescopes. Infrared telescopes (2MASS) have penetrated the dusty veil and examined the unseen structure inside the Flame. Behind the thick dark lane which splits the two halves of the Flame is a rich cluster of new stars all younger than 1 million years old. The young stars are only visible at infrared wavelengths. At least half the stars are noted to have circumstellar accretion disks, possibly the precursors of terrestrial earthlike planets. Recent work has identified a central massive star, either a late O type or early B type (IRS2b) as the sole ionizing source of the Flame Nebula.

Alnitak ( Zeta Orionis) the most eastern star of the belt stars of Orion is a remarkable tertiary star system in its own right. Alnitak A, the dominant element of the complex star system is a hot blue supergiant, and is the brightest O type star in the sky. Visually its brightness is 10,000 times that of our sun, however its surface temperature of 31,000 degrees Kelvin causes it to radiate mostly in ultraviolet light which the eye cannot see. Taking the UV emission into account, Alnitak A is 100,000 times more luminous than our sun. The brilliance of Alnitak A can only come from the stars great mass which is 20 times that of our sun. At an age of 6 million years Alnitak A is already old for a supergiant, its hydrogen fuel almost depleted. It will certainly end its life in a great supernova returning all its material to the interstellar medium.

The Alnitak B component is a B type star only 2.4 arc seconds from the A component. The two orbit each other with a periodicity of several thousand years. Recent observations from the Navy Prototype Optical Interferometer (NPOI) have revealed an even more intimate companion to Alnitak A, lying only 0.04 arc seconds away. This star is only two magnitudes dimmer than its close neighbor and would easily be visible to the unaided eye if not for the brilliant light of its companion.