neufer wrote: ↑
Sat Nov 02, 2019 11:59 am
<<The Flame Nebula, designated as NGC 2024 and Sh2-277, is an emission nebula in the constellation Orion.
The bright star Alnitak (ζ Ori), the easternmost star in the Belt of Orion, shines energetic ultraviolet light into the Flame and this knocks electrons away from the great clouds of hydrogen gas that reside there.
Much of the glow results when the electrons and ionized hydrogen recombine. Additional dark gas and dust lies in front of the bright part of the nebula and this is what causes the dark network that appears in the center of the glowing gas. The Flame Nebula is part of the Orion Molecular Cloud Complex, a star-forming region that includes the famous Horsehead Nebula.
At the center of the Flame Nebula is a cluster of newly formed stars, 86% of which have circumstellar disks. X-ray observations by the Chandra X-ray Observatory show several hundred young stars, out of an estimated population of 800 stars. X-ray and infrared images indicate that the youngest stars are concentrated near the center of the cluster.>>
The Horsehead and Flame nebula (left). Photo:
The Flame nebula. Source:
X-ray: NASA/CXC/PSU/K.Getman, E.Feigelson, M.Kuhn & the MYStIX team;
One of my objections to the idea of Alnitak being the main ionizing source of the Flame nebula is that the Flame nebula is yellowish in color, and clearly yellower than the Hα nebula making up the background for the Horsehead nebula. If both the Horsehead nebula background and the Flame nebula are emission nebulas ionized by external sources, why would one nebula be so much yellower than the other one?
The yellow color of the Flame nebula might be at least partly explained if we assume that the Flame nebula is a combined red emission and blue reflection nebula being dust-reddened from within. A pure red Hα nebula, by contrast, can't be reddened into a yellow color.
Another of my objections to the idea of Alnitak being the prime ionizing source of the Flame nebula is that the inner workings and structures of the Flame nebula are so symmetrical and so centered on the central inner cluster. By far most of the energy of this nebula seems to come from within, from the embedded cluster, and not from an outside source off to one side.
So I believe that Alnitak is playing second fiddle when it comes to ionizing the Flame.