by Ann » Thu May 14, 2015 4:24 am
inertnet wrote:Can someone explain where the pink halo around the head comes from? Is that an image enhancement artifact? It doesn't seem to belong to the head, is it something in the line of sight behind the head? It doesn't seem 'natural' to me because the head has dark edges.
It is not an artifact. Other dust pillars evaporating due to strong ultraviolet light also have pink halos.
Here is another example, the Dark Tower in Scorpius.
The pink halos must be due to hydrogen emission. Structures like the Horsehead Nebula and the Dark Tower contain not only dust, but also a lot of gas. As the dust "crumbles" due to the harsh ultraviolet light, the gas gets more exposed, and it starts fluorescing its typical red Ha and green Hβ light, whose combined color is pink.
The Horsehead is seen against a backdrop of hydrogen emission. But the Horsehead also has a halo of its own Ha plus Hβ emission, which makes the reddish-pink light around the Horsehead brighter than the background.
Ann
[quote="inertnet"]Can someone explain where the pink halo around the head comes from? Is that an image enhancement artifact? It doesn't seem to belong to the head, is it something in the line of sight behind the head? It doesn't seem 'natural' to me because the head has dark edges.[/quote]
It is not an artifact. Other dust pillars evaporating due to strong ultraviolet light also have pink halos. [url=http://apod.nasa.gov/apod/ap110427.html]Here[/url] is another example, the Dark Tower in Scorpius.
The pink halos must be due to hydrogen emission. Structures like the Horsehead Nebula and the Dark Tower contain not only dust, but also a lot of gas. As the dust "crumbles" due to the harsh ultraviolet light, the gas gets more exposed, and it starts fluorescing its typical red Ha and green Hβ light, whose combined color is pink.
The Horsehead is seen against a backdrop of hydrogen emission. But the Horsehead also has a halo of its own Ha plus Hβ emission, which makes the reddish-pink light around the Horsehead brighter than the background.
Ann