APOD: Fox Fur, Unicorn, and Christmas Tree (2020 Dec 26)

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APOD: Fox Fur, Unicorn, and Christmas Tree (2020 Dec 26)

Post by APOD Robot » Sat Dec 26, 2020 5:05 am

Image Fox Fur, Unicorn, and Christmas Tree

Explanation: Clouds of glowing hydrogen gas fill this colorful skyscape in the faint but fanciful constellation Monoceros, the Unicorn. A star forming region cataloged as NGC 2264, the complex jumble of cosmic gas and dust is about 2,700 light-years distant and mixes reddish emission nebulae excited by energetic light from newborn stars with dark interstellar dust clouds. Where the otherwise obscuring dust clouds lie close to the hot, young stars they also reflect starlight, forming blue reflection nebulae. The telescopic image spans about 1.5 degrees or 3 full moons, covering nearly 80 light-years at the distance of NGC 2264. Its cast of cosmic characters includes the the Fox Fur Nebula, whose dusty, convoluted pelt lies left of center, bright variable star S Monocerotis immersed in the blue-tinted haze near center, and the Cone Nebula pointing in from the right side of the frame. Of course, the stars of NGC 2264 are also known as the Christmas Tree star cluster. The triangular tree shape is seen on its side here. Traced by brighter stars it has its apex at the Cone Nebula. The tree's broader base is centered near S Monocerotis.

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Ann
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Re: APOD: Fox Fur, Unicorn, and Christmas Tree (2020 Dec 26)

Post by Ann » Sat Dec 26, 2020 7:44 am

ChristmasTree-ConeNebula-CumeadaObservatoryDSA-net1100[1].jpg
The Christmas Tree and Cone Nebula region.
Photo: Miguel Claro.
NGC 2264 annotated Miguel Claro.png
Snowflake Cluster Spitzer.png
Star formation in the Christmas Tree Cluster.
Photo: Spitzer.
Today's APOD is superb! :D

Let's look at some of the objects in it.

1) This is the overall "Christmas Tree" outline.

2) This is the magnificent O7-type star S Monocerotis, or S Mon, or 15 Monocerotis, or 15 Mon.

3) This is the Fox Fur Nebula. Note how "thin" it is. It is being eroded by the harsh stellar wind of S Mon.

4) This is a dusty blue reflection nebula, illuminated by the blue brilliance of S Mon.

5) This is a soft yellowish glow emitted by baby stars still embedded in dust.

6) This is (of course) the Cone Nebula. The Cone Nebula is a typical "pillar" carved by the stellar wind of hot stars. It is similar to the Horsehead Nebula and the Pillars of Creation. The Cone Nebula is being carved by S Mon.

7) This arc is not a pillar, but it is still a sort of counterpart to the Cone Nebula. It, too, is being sculpted by S Mon.

8) This is Hubble's Variable Nebula. It is illuminated by a young, still unborn T Tauri star, which is believed to be surrounded by dust clouds that move in front of the star, casting shadows and causing the illumination of the reflection nebula to vary.


Finally, let's take a look at the Spitzer Telescope's infrared image of NGC 2264, which reveals star formation here.

1) This is the Cone Nebula.

2) This is the Snowflake Cluster, an embedded cluster of baby stars that have not yet been born. The light from the Snowflake Cluster is seen as a faint diffuse yellowish glow in optical images, like the APOD.

3) This is a ridge close to the Snowflake Cluster. It may well have been sculpted by these young stars.

4) This is the Fox Fur Nebula.

5) Somewhere in here is S Mon. It looks very insignificant in infrared light!

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!

Ann
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Re: APOD: Fox Fur, Unicorn, and Christmas Tree (2020 Dec 26)

Post by orin stepanek » Sat Dec 26, 2020 2:01 pm

Hard for me to see the Fox Nebula here! :shock:

ChristmasTree-ConeNebula-CumeadaObservatoryDSA-net1100.jpg

Ah this is better! :D

Foxfur_Vermette_1080.jpg
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Re: APOD: Fox Fur, Unicorn, and Christmas Tree (2020 Dec 26)

Post by Tszabeau » Sat Dec 26, 2020 2:34 pm

That must be Santa’s Sleigh in the upper right quadrant.

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Re: APOD: Fox Fur, Unicorn, and Christmas Tree (2020 Dec 26)

Post by johnnydeep » Sat Dec 26, 2020 4:39 pm

orin stepanek wrote:
Sat Dec 26, 2020 2:01 pm
Hard for me to see the Fox Nebula here! :shock:


ChristmasTree-ConeNebula-CumeadaObservatoryDSA-net1100.jpg


Ah this is better! :D


Foxfur_Vermette_1080.jpg
Are these oriented the same way? I'm having a hard time seeing that they have anything in common at all :(
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Re: APOD: Fox Fur, Unicorn, and Christmas Tree (2020 Dec 26)

Post by Ann » Sat Dec 26, 2020 8:59 pm

johnnydeep wrote:
Sat Dec 26, 2020 4:39 pm
orin stepanek wrote:
Sat Dec 26, 2020 2:01 pm
Hard for me to see the Fox Nebula here! :shock:


ChristmasTree-ConeNebula-CumeadaObservatoryDSA-net1100.jpg


Ah this is better! :D


Foxfur_Vermette_1080.jpg
Are these oriented the same way? I'm having a hard time seeing that they have anything in common at all :(
As you guessed, they are not oriented the same way at all.

In today's APOD, the Fox Fur Nebula is to the upper right of bright star S Mon, but in the picture that Orin posted (which is itself an APOD, from December 30, 2015) the Fox Fur Nebula is to the lower left of the bright star S Mon.

Ann
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Re: APOD: Fox Fur, Unicorn, and Christmas Tree (2020 Dec 26)

Post by heehaw » Sat Dec 26, 2020 9:12 pm

What a fantastic universe out there. But did it have to be the way it is? Maybe not! How was it decided what the mass of the electron is? NO ONE KNOWS! Suppose it were slightly different? What would our universe look like? No you, no me.
Frank Wilczek:

page 200 of his book “The Lightness of Being” gives us:

The mass of the electron, although it contributes much less than 1% of the total mass of ordinary matter, is indispensable.

The value of the electron’s mass determines the size of atoms.

If you doubled the electron’s mass, all atoms would contract to half their size;
if you halved the electron’s mass, all atoms would expand to twice their size. …

If electrons were heavier by a factor of 4 or so, then it would be favorable for electrons to combine with protons to make neutrons, emitting neutrinos. That would be RIP for chemistry.

…up and down quarks, u and d. They make a quantitatively small but qualitatively crucial contribution to the masses of protons and neutrons, …


Those are quotes from his book. In fact, if u and d were massless, they would join their gluons in moving at the speed of light … and we’d all go poof!

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Re: APOD: Fox Fur, Unicorn, and Christmas Tree (2020 Dec 26)

Post by MarkBour » Sat Dec 26, 2020 10:47 pm

Ann wrote:
Sat Dec 26, 2020 7:44 am
Today's APOD is superb! :D

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!

Ann
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.


capture1.jpg
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.

capture1.jpg

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 .

(Source http://simbad.u-strasbg.fr/simbad/sim-id?Ident=hd47887).
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.







capture2.jpg


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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Last edited by MarkBour on Sat Dec 26, 2020 10:57 pm, edited 1 time in total.
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Re: APOD: Fox Fur, Unicorn, and Christmas Tree (2020 Dec 26)

Post by johnnydeep » Sat Dec 26, 2020 10:55 pm

Ann wrote:
Sat Dec 26, 2020 8:59 pm
johnnydeep wrote:
Sat Dec 26, 2020 4:39 pm
orin stepanek wrote:
Sat Dec 26, 2020 2:01 pm
Hard for me to see the Fox Nebula here! :shock:


ChristmasTree-ConeNebula-CumeadaObservatoryDSA-net1100.jpg


Ah this is better! :D


Foxfur_Vermette_1080.jpg
Are these oriented the same way? I'm having a hard time seeing that they have anything in common at all :(
As you guessed, they are not oriented the same way at all.

In today's APOD, the Fox Fur Nebula is to the upper right of bright star S Mon, but in the picture that Orin posted (which is itself an APOD, from December 30, 2015) the Fox Fur Nebula is to the lower left of the bright star S Mon.

Ann
Thanks! But I was still struggling to relate the two until it dawned on me that the brightest star in each image really IS S Mon (yeah, even that wasn't obvious to me: I've been fooled before by assuming the brightest star in two images of the same general area were identical). So, after accepting that, I used two sets of smaller similarly spaced stars in both images to rotate the older APOD to match today's. This is the result, with those "alignment helper" stars indicated by red arcs:

S Mon and Friend Stars in two different APOD images both including the Fox Fur Nebula.JPG
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Re: APOD: Fox Fur, Unicorn, and Christmas Tree (2020 Dec 26)

Post by orin stepanek » Sun Dec 27, 2020 1:54 am

Thanks Ann!
Orin

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Re: APOD: Fox Fur, Unicorn, and Christmas Tree (2020 Dec 26)

Post by Ann » Sun Dec 27, 2020 7:57 am

Thank you for that highly informative and fascinating post, Mark! :D

And thank you for rotating "Orin's APOD" so that we can compare it with the APOD of December 26, 2020, Johnny! :D

Ann
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