The Flame Nebula (NGC 2024) is located at a distance of 1 400 light years. It is part of the Orion Molecular Cloud Complex, a star-forming region that includes the famous Horsehead Nebula. Within the Flame Nebula is Alnitak or Zeta Orionis (ζ Ori), the brightest star in the upper right of the nebula. Alnitak is the easternmost star of the three bright stars in Orion's belt. It emits energetic ultraviolet radiation which ionizes the surrounding hydrogen gas clouds. Beneath the Flame Nebula is the large, dark dust cloud of Nebula NGC 2023 in which a magnitude 8.5 star scatters wide surface light.
The stars of the NGC 2024 group that lie in the center of the nebula are around 200,000 years old, while those on the periphery are around 1.5 million years old. The stars at the periphery of this group are therefore older than those in the central regions and this goes against what we thought about the formation of stars. Stars are first born in the center of a collapsing cloud. One explanation proposes that star formation continues to occur in the interior regions. This may occur because the gas in the outer regions is thinner and more diffuse than in the inner regions. Over time, the density of the gas is below a threshold value and it can no longer condense to form stars. Star formation ceases in the outer regions while it continues in the inner regions, leading to a concentration of young stars.
These images were taken by VISTA, the telescope at ESO's Cerro Paranal Observatory in the Atacama Desert in northern Chile. The red color of this nebula is due to the luminosity of ionized hydrogen atoms.
note: VISTA is located on a summit close to that of the VLT. VISTA's main mirror has a diameter of 4.1 meters. Its 3-tonne camera cooled to – 200 degrees Celsius are sensitive to infrared radiation. This asset allows him to observe objects impossible to see in visible light, hidden behind clouds. of dust. VISTA devotes much of its time to mapping the southern sky in detail. It also maps in three dimensions the structure of our Galaxy and the Magellanic Clouds.