Ann wrote: ↑Sat Dec 26, 2020 7:44 am
Today's APOD is superb!
Let's look at some of the objects in it.
. . .
Finally, what is that brilliant glow just above the Cone Nebula in the Spitzer image? I haven't the faintest idea. I would guess, however, that it is an embedded star that is very bright indeed in the infrared. If you take a look at the full resolution of the APOD, you can see that there is a blue star just "above" (or to the left of) the tip of the Cone Nebula, and just "above" (or to the left of) that blue star, you can actually see a very faint, small yellow glow. That yellow glow is obviously the visual counterpart to that brilliant infrared glow.
And that's all for me now!
Thanks for the very informative "tour", Ann.
You ended it with the above comments that left a couple of questions in my mind, and these prompted me to do a little online searching. The following does confirm what you've said in that last paragraph, with some added names and thoughts.
As I look at the Cone Nebula, I'm not just struck by its unusual shape, but also by the fact that in APODs about it, the captions wondered out loud about what forces shaped it. I don't know why this one is considered mysterious. I probably just don't know enough about it to appreciate it. But I have the following thoughts about it.
Whenever one has the dramatic geological features on earth of badlands, monuments, or hoodoos, they are the result of a contrast. There is a process of erosion
, and a case of resistance
to erosion. So, in the picture at right, wind has eroded away the majority of a rocky structure. As the material is carved away, some of it emerges as more durable than the rest, and so it remains standing alone for some time.
Looking at the Cone Nebula, embedded in the tip of the cone are some T-Tau type stars that appear to be very young and just beginning to shine out. These are beautifully imaged in a favorite image for previous APODs, labelled: "Cone Nebula from Hubble" or "Cone Nebula Close Up"
I assume that these (and possibly other, as yet invisible stars inside the nebula) were formed by gravitation having been seeded to a sufficient level that the region of the cone resisted being carved away by outside forces. These nearly-formed stars had reached the point where their gravity was the resistive force that prevented the material in the cone from being swept away. Of course once these stars themselves mature, they will change the dynamic and will probably blow away the dust that has been held until now.
Meanwhile, what has been causing an eroding force in the area? It would seem it must be a source above the tip of the cone shape. Such a force would have pushed away dust in the region, in all directions from the source, but would have left the cone as a pillar of dust. Most obviously, the tip of the cone is pointed at what at first may appear to be a single bright star. Right there is HD 47887. It is a blue giant of spectral class B2III: C .
It has been estimated at 9.6 solar masses.
But when one zooms in, one can see that there are multiple stars there. CI*NGC 2264 VAS 133 is visually right on top of HD 47887 and there are others as well. It seems reasonable to me that these stars are providing a combined stellar wind in the area and that this is the eroding force that mainly produced the Cone Nebula.
However, there is a strong Infrared source in the area that is almost undetectable in visible light. It is designated NGC 2264 IRS. From our perspective, it is about twice as far from the tip of the cone as is HD 47887. This is likely the bright infrared source you were pointing out, Ann. (See https://apod.nasa.gov/apod/ap970611.html
.) It has been investigated and it turns out to be multiple young stellar objects as well. There is a main object, labelled "1", and then 6 or more smaller sources around it, considered to be smaller siblings.
At the right is figure 3 from https://iopscience.iop.org/article/10.1 ... 6.fg3.html
I guess some astronomers think that this is the source of the force of erosion sculpting the cone. But these young objects do not appear to have cleared out their own shells, so I don't see how they could have cleared a much larger area.
P.S. Today is a great day to put up an APOD about the Cone Nebula and the Christmas Tree Nebula. It was this day (December 26) in 1785 that it was discovered by William Herschel.
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