APOD: A Fox Fur, a Unicorn, and a Tree... (2012 Apr 10)

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APOD: A Fox Fur, a Unicorn, and a Tree... (2012 Apr 10)

Postby APOD Robot » Tue Apr 10, 2012 4:06 am

Image A Fox Fur, a Unicorn, and a Christmas Tree

Explanation: What do the following things have in common: a cone, the fur of a fox, and a Christmas tree? Answer: they all occur in the constellation of the unicorn (Monoceros). Pictured above as 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 above image spans about 3/4 degree or nearly 1.5 full moons, covering 40 light-years at the distance of NGC 2264. Its cast of cosmic characters includes the Fox Fur Nebula, whose convoluted pelt lies at the upper left, bright variable star S Mon immersed in the blue-tinted haze just below the Fox Fur, and the Cone Nebula near the tree's top. Of course, the stars of NGC 2264 are also known as the Christmas Tree star cluster. The triangular tree shape traced by the stars appears sideways here, with its apex at the Cone Nebula and its broader base centered near S Mon.

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Re: APOD: A Fox Fur, a Unicorn, and a Tree... (2012 Apr 10)

Postby Beyond » Tue Apr 10, 2012 4:42 am

The animation of the variable star makes it seem like it's breathing. 8-)
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Re: APOD: A Fox Fur, a Unicorn, and a Tree... (2012 Apr 10)

Postby Ann » Tue Apr 10, 2012 6:21 am

This is a wonderful portrait of the complex nebulosity surrounding a young cluster of OB stars. All the red emission nebulosity is caused by hot blue stars, whose ultraviolet photons ionize hydrogen atoms, making them glow red.

As a "blue star freak", I always check out the star colors in any portrait of the night sky. The most important star here is, of course, S Monocerotis. S Mon is the chief ionizer of the nebulosity here. S Mon is also a very blue star, having one of the bluest B-V indexes of all naked-eye stars. Yet in this picture S Mon doesn't look particularly blue at all. Why is that?

The reason, as always, is the filters used. The image was made by combining 25 x 1200 sec Ha / 22 x 1200 sec OIII / 6 x 1200 sec SII / 1 x 300 sec RGB. Ha is of course red hydrogen alpha, OIII is blue-green oxygen emission and SII is red ionized sulphur. Most of the exposure time was spent on these "nebulosity filters". It is likely that there is not very much OIII emission in NGC 2264, for the simple reason that there is just too much gas and dust here, and OIII emission demands rarefied conditions. It is likely, on the other hand, that much or possibly most of the red nebulosity that we can see in today's APOD is red sulphur emission. SII emission is all but identical in color to Ha, but represents a lower degree of ionization, and is fainter. Without an SII filter suphur emission is rarely seen at all in RGB images.

Stars produce red sulphur emission, too, and it is a known fact that star colors get changed when an SII filter is used. That's why S Mon doesn't look blue in this image.

But the nebular "landscape" - or "skyscape" - is amazing.

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Re: APOD: A Fox Fur, a Unicorn, and a Tree... (2012 Apr 10)

Postby agulesin » Tue Apr 10, 2012 7:05 am

Some people have amazing imagination! I could see neither the fur of a fox, nor a Christmas tree in this super starscape... Oh well, better just sit back and enjoy the view!
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Re: APOD: A Fox Fur, a Unicorn, and a Tree... (2012 Apr 10)

Postby Vulpine » Tue Apr 10, 2012 12:08 pm

The description confuses me as the image, at least to my eye, has the Christmas tree upright. The upper left portion of the overall image is very plain and featureless while the lower left near the base of the apparent tree has both the head of the fox and the unicorn.

Could someone possible repost the image with annotations to either confirm or correct my viewpoints?
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Re: APOD: F.F.,U.,C.T. again (2012 Apr 10)

Postby neufer » Tue Apr 10, 2012 12:16 pm

Vulpine wrote:
The description confuses me as the image, at least to my eye, has the Christmas tree upright. The upper left portion of the overall image is very plain and featureless while the lower left near the base of the apparent tree has both the head of the fox and the unicorn.

Could someone possible repost the image with annotations to either confirm or correct my viewpoints?

Explanation: What do the following things have in common:

http://apod.nasa.gov/apod/ap100406.html
http://apod.nasa.gov/apod/ap120410.html
Last edited by neufer on Tue Apr 10, 2012 2:15 pm, edited 2 times in total.
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Re: APOD: A Fox Fur, a Unicorn, and a Tree... (2012 Apr 10)

Postby Indigo_Sunrise » Tue Apr 10, 2012 12:51 pm

While TPTB updated most of the description/explanation from this APOD, they should have changed the part about the convoluted pelt that
"lies at the upper left,"

to:
"...lies almost at the center of the image."


To me, the 'feature' in the upper left of today's image looks more like a whirlpool or an almost side-view of a flower, and was confusing me.... :(


But a very interesting and detailed image!
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Re: APOD: A Fox Fur, a Unicorn, and a Tree... (2012 Apr 10)

Postby orin stepanek » Tue Apr 10, 2012 1:02 pm

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Re: APOD: A Fox Fur, a Unicorn, and a Tree... (2012 Apr 10)

Postby Locutus76 » Tue Apr 10, 2012 1:10 pm

Indigo_Sunrise wrote:While TPTB updated most of the description/explanation from this APOD, they should have changed the part about the convoluted pelt that
"lies at the upper left,"

to:
"...lies almost at the center of the image."


To me, the 'feature' in the upper left of today's image looks more like a whirlpool or an almost side-view of a flower, and was confusing me.... :(


But a very interesting and detailed image!
:thumb_up:


The image is confusing because the text below actually belongs to the April 6, 2010 image, which is rotated 90 degrees to the right compared to the April 10, 2012 image. I had the same problem
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Re: APOD: A Fox Fur, a Unicorn, and a Tree... (2012 Apr 10)

Postby Donald Pelletier » Tue Apr 10, 2012 2:15 pm

Comments on the positions would be accurate if the image was inverted from top to bottom.
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Re: APOD: A Fox Fur, a Unicorn, and a Tree... (2012 Apr 10)

Postby TNT » Tue Apr 10, 2012 2:22 pm

Nice image, with lots of detail. I too was confused with the positions of the objects and where the text located them. People must have different views of what these objects look like, as I do not see a star cluster shaped like a christmas tree but rather the nebula looks like one to me. What appears to be the Fox Fur Nebula seems to be the trunk of the tree.
Last edited by TNT on Wed Apr 11, 2012 3:29 am, edited 1 time in total.
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Re: APOD: A Fox Fur, a Unicorn, and a Tree... (2012 Apr 10)

Postby Vulpine » Tue Apr 10, 2012 4:39 pm

So they simply reposted the image, rotated 90° to the left and zoomed out a bit. To me the whole nebula area looks like a lighted Christmas tree in the newer image which puts the fox almost under its branches and a unicorn ornament hanging about halfway up the right side. The cone at the top is the star at the top of the tree.
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Re: APOD: A Fox Fur, a Unicorn, and a Tree... (2012 Apr 10)

Postby neufer » Tue Apr 10, 2012 7:28 pm

Vulpine wrote:
So they simply reposted the image, rotated 90° to the left and zoomed out a bit.

It is a whole NEW image in which the bright variable star
S Mon is NOT really immersed in the blue-tinted haze.
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Re: APOD: A Fox Fur, a Unicorn, and a Tree... (2012 Apr 10)

Postby emc » Tue Apr 10, 2012 8:21 pm

I see a horse head - quite large, in the mid lower left of the tree with eyes, ears, nostrils, the whole head, bright red, just below the blue. Even part of the body is there. Reminds me of one of my relatives.
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Re: APOD: A Fox Fur, a Unicorn, and a Tree... (2012 Apr 10)

Postby RJN » Tue Apr 10, 2012 8:36 pm

Yes, sorry about the text. The image is new but the text was indeed adapted from a previous APOD description of a similar but possibly less spectacular image rotated 90 degrees. I have just tried to fix it. My apologies. - RJN
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Re: APOD: A Fox Fur, a Unicorn, and a Tree... (2012 Apr 10)

Postby Case » Tue Apr 10, 2012 9:21 pm

I tried to identify the various objects in the image. I think I got them. But I welcome any corrections.
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The Snowflake Cluster

Postby neufer » Wed Apr 11, 2012 12:11 am

http://www.spitzer.caltech.edu/images/2 ... ke-Cluster wrote:
<<Newborn stars, hidden behind thick dust, are revealed in this image of a section of the Christmas Tree Cluster from NASA's Spitzer Space Telescope, created in joint effort between Spitzer's Infrared Array Camera (IRAC) and Multiband Imaging Photometer (MIPS) instruments.

The newly revealed infant stars appear as pink and red specks toward the center of the combined IRAC-MIPS image (left panel). The stars appear to have formed in regularly spaced intervals along linear structures in a configuration that resembles the spokes of a wheel or the pattern of a snowflake. Hence, astronomers have nicknamed this the "Snowflake Cluster."

Star-forming clouds like this one are dynamic and evolving structures. Since the stars trace the straight line pattern of spokes of a wheel, scientists believe that these are newborn stars, or "protostars." At a mere 100,000 years old, these infant structures have yet to "crawl" away from their location of birth. Over time, the natural drifting motions of each star will break this order, and the snowflake design will be no more.

While most of the visible-light stars that give the Christmas Tree Cluster its name and triangular shape do not shine brightly in Spitzer's infrared eyes, all of the stars forming from this dusty cloud are considered part of the cluster.Like a dusty cosmic finger pointing up to the newborn clusters, Spitzer also illuminates the optically dark and dense Cone Nebula, the tip of which can be seen towards the bottom left corner of each image.

IRAC's near and mid-infrared eyes (top right) show that the nebula is still actively forming stars. The wisps of red (represented as green in the IRAC-MIPS image) are organic molecules mixed with dust, which has been illuminated by nearby star formation. The IRAC picture is a four-channel, false-color composite, showing emission from wavelengths of 3.6 microns (blue), 4.5 microns (green), 5.8 microns (orange) and 8.0 microns (red).

MIPS' far-infrared eyes (bottom right) the colder dust of the nebula and unwraps the youngest stellar babies from their dusty covering. This is a false-color image showing emission at 24 microns (red).>>
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Re: APOD: A Fox Fur, a Unicorn, and a Tree... (2012 Apr 10)

Postby Ann » Wed Apr 11, 2012 5:23 am

Case wrote:

I tried to identify the various objects in the image. I think I got them. But I welcome any corrections.


You got them, Case. :clap:

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Re: APOD: A Fox Fur, a Unicorn, and a Tree... (2012 Apr 10)

Postby ro_star » Wed Apr 11, 2012 5:52 am

yes, I clearly see the red dragon at the top and 3 red lionesses in triangle formation below, all right side up; also at the top left corner an arc shaped shockwave that could resemble something possibly unprintable
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Re: APOD: A Fox Fur, a Unicorn, and a Tree... (2012 Apr 10)

Postby geissi » Wed Apr 11, 2012 2:01 pm

Hello,

I'm Rolf Geissinger, the astro-photographer of this Christmas-Tree APOD.
Thanks a lot for your interested discussions on my image.
My goal was, to achive a very deep and wide view around the christmas-tree cluster.
It's amazing, how much "matter" there is around.

I just had the same idea as "case" to make an identify-image for better locating several included objects.
Thanks to "case" for this work. Well done!

If you have a close look, you can even see the fox's eyes and nose :-)

Have a nice day!

Regards
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Re: APOD: A Fox Fur, a Unicorn, and a Tree... (2012 Apr 10)

Postby neufer » Wed Apr 11, 2012 2:31 pm

geissi wrote:
If you have a close look, you can even see the fox's eyes and nose :-)

http://apod.nasa.gov/apod/ap080422.html

P.S., fascinating S MONOCEROTIS writeup:
http://stars.astro.illinois.edu/sow/15mon.html
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Re: APOD: A Fox Fur, a Unicorn, and a Tree... (2012 Apr 10)

Postby DavidLeodis » Wed Apr 11, 2012 9:28 pm

I've just been looking at the Exif information for the image. In the history it states numerous times starting at 2012:03:17 14:08:11 +1.00 through to 2012:03:17 22:13:01 +1.00. There is then a clear break in what I assume are the exposure times as the next date/time is 2012:03:18 10:50:47 +1.00 through to 2012:03:18 14:28:43 +1.00. Unless I am misunderstanding something (the +1.00 is 1 hour ahead of GMT) then most of the image data was acquired during daylight at the Remseck, Germany, location. In Rolf's Geissinger's website it stated with the image "Exposure: 25 x 1200 sec Ha / 22 x 1200 sec OIII / 6 x 1200 sec SII / 1 x 300 sec RGB - Total exposure approx. 20 hours". I had not realised that image data can be obtained during daylight :!:. I assume therefore that Ha, OIII and SII filters do not need darkness. :oops: but still trying to :)
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Re: APOD: A Fox Fur, a Unicorn, and a Tree... (2012 Apr 10)

Postby Chris Peterson » Thu Apr 12, 2012 12:58 am

DavidLeodis wrote:I've just been looking at the Exif information for the image. In the history it states numerous times starting at 2012:03:17 14:08:11 +1.00 through to 2012:03:17 22:13:01 +1.00. There is then a clear break in what I assume are the exposure times as the next date/time is 2012:03:18 10:50:47 +1.00 through to 2012:03:18 14:28:43 +1.00. Unless I am misunderstanding something (the +1.00 is 1 hour ahead of GMT) then most of the image data was acquired during daylight at the Remseck, Germany, location. In Rolf's Geissinger's website it stated with the image "Exposure: 25 x 1200 sec Ha / 22 x 1200 sec OIII / 6 x 1200 sec SII / 1 x 300 sec RGB - Total exposure approx. 20 hours". I had not realised that image data can be obtained during daylight :!:. I assume therefore that Ha, OIII and SII filters do not need darkness. :oops: but still trying to :)

The image data was collected with a setup that doesn't record EXIF data. Anything you find in the EXIF header was added by the image processing software, after the data was collected. The data itself was collected over more than one night.

That said, you can't really trust the time in EXIF headers. Different cameras and software handle UT offsets differently, if at all. And some people never bother to set the clock correctly in the first place.
Chris

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Re: APOD: A Fox Fur, a Unicorn, and a Tree... (2012 Apr 10)

Postby DavidLeodis » Thu Apr 12, 2012 1:06 pm

Thanks Chris. Your help is appreciated. :)
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