APOD: The Eagle Nebula from Kitt Peak (2012 Apr 16)

Comments and questions about the APOD on the main view screen.
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APOD Robot
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APOD: The Eagle Nebula from Kitt Peak (2012 Apr 16)

Post by APOD Robot » Mon Apr 16, 2012 4:06 am

Image The Eagle Nebula from Kitt Peak

Explanation: From afar, the whole thing looks like an Eagle. A closer look at the Eagle Nebula, however, shows the bright region is actually a window into the center of a larger dark shell of dust. Through this window, a brightly-lit workshop appears where a whole open cluster of stars is being formed. In this cavity tall pillars and round globules of dark dust and cold molecular gas remain where stars are still forming. Already visible are several young bright blue stars whose light and winds are burning away and pushing back the remaining filaments and walls of gas and dust. The Eagle emission nebula, tagged M16, lies about 6500 light years away, spans about 20 light-years, and is visible with binoculars toward the constellation of the Serpent (Serpens). This picture combines three specific emitted colors and was taken with the 0.9-meter telescope on Kitt Peak, Arizona, USA.

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Flase
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Re: APOD: The Eagle Nebula from Kitt Peak (2012 Apr 16)

Post by Flase » Mon Apr 16, 2012 4:26 am

Always a good one this. Pictures like this make good posters for children to lie in bed looking at the shapes, meditating.

I often find with these images that the high res version is too big. All I see is the graininess and blemishes and it would be better shrunk down a bit to where that graininess goes away...

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Re: APOD: The Eagle Nebula from Kitt Peak (2012 Apr 16)

Post by nstahl » Mon Apr 16, 2012 8:39 am

I agree Flase. The screen-filling version I get on the first click is very good but the zoomed-in, largest version is grainy and hazy, and a smaller biggest version would be better if that were convenient. But it's a great APOD.

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Re: APOD: The Eagle Nebula from Kitt Peak (2012 Apr 16)

Post by henrystar » Mon Apr 16, 2012 9:34 am

The fingers pointing inward are the results of Rayleigh-Taylor instability - cold, dense on one side; hot, tenuous on the other. Any slight perturbation feeds on itself with the result you see in the picture. Is it not wonderful that we not only see these glorious structures, we understand them as well?

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Re: APOD: The Eagle Nebula from Kitt Peak (2012 Apr 16)

Post by orin stepanek » Mon Apr 16, 2012 12:28 pm

Eagle Nebula always neat! 8-)

Smart dog: keeping cool! :mrgreen: 8-)
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Re: APOD: The Eagle Nebula from Kitt Peak (2012 Apr 16)

Post by Beyond » Mon Apr 16, 2012 2:14 pm

Hey orin, looks like he's a real 'fan' of the star wind blowing in the eagle nebula. He must be a space-bird-dog :!: :lol:
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Re: APOD: The Eagle Nebula from Kitt Peak (2012 Apr 16)

Post by DavidLeodis » Tue Apr 17, 2012 1:18 pm

In the picture's explanation it states "Already visible are several young bright blue stars". I would be grateful if someone could please indicate where those blue stars are as I see lots of pink stars but no obviously blue ones. Perhaps my monitor's colour wants adjusting, though I think it is OK.

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Re: APOD: The Eagle Nebula from Kitt Peak (2012 Apr 16)

Post by geckzilla » Tue Apr 17, 2012 3:02 pm

David, the pink stars are actually blue. Your monitor isn't acting up and neither are your eyes. It's just the way the three different filters were assigned colors that makes them appear pink. The ones which appear more red than pink are probably the non blue ones. There's two bright stars top center you can use to train your eyes. The one near the top edge is more blue while the one just below it is more red.
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Re: APOD: The Eagle Nebula from Kitt Peak (2012 Apr 16)

Post by Ann » Tue Apr 17, 2012 3:22 pm

This picture was made using the Hubble palette. The Eagle Nebula was imaged through a blue-green OIII filter, a red Ha filter and an almost equally red SII filter. The picture taken through the blue-green OIII filter was mapped as blue, the picture taken through the red Ha filter was mapped as green, and the picture taken through the red SII filter was mapped as red. I read somewhere - but maybe I misunderstood it - that when astronomers use these filters and these mapped colors to produce the Hubble palette, then the sulphur emission becomes so dominant that anything that emits red sulphur light, such as blue stars, appears pink.

Personally I'm no fan of the Hubble palette, precisely because it makes blue stars look pink. Personally I find it jarring. But the Hubble palette is great for bringing out details in the nebulosity.

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Re: APOD: The Eagle Nebula from Kitt Peak (2012 Apr 16)

Post by DavidLeodis » Tue Apr 17, 2012 4:48 pm

Thanks geckzilla and Ann. Your help is appreciated. With the mention of blue stars in the explanation I had expected to obviously see such things in the image so I was surprised that I did not, but as nobody had mentioned it I did wonder if my monitor was at fault which it thankfully is not. :)

It's a shame that, as far as I know, space is not coloured like it is seen in photos. It would be very pretty out there if it was. :D

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Re: APOD: The Eagle Nebula from Kitt Peak (2012 Apr 16)

Post by geckzilla » Tue Apr 17, 2012 4:53 pm

It is colored like that if you have ultra-sensitive, oxygen, sulfur, hydrogen detectors for eyes. :shock: <= I imagine they'd be quite large eyes.
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Re: APOD: The Eagle Nebula from Kitt Peak (2012 Apr 16)

Post by DavidLeodis » Tue Apr 17, 2012 5:05 pm

geckzilla wrote:It is colored like that if you have ultra-sensitive, oxygen, sulfur, hydrogen detectors for eyes. :shock: <= I imagine they'd be quite large eyes.
:) A bit like other animals and insects that see things in colours that we cannot. I wonder how a dark clear night sky looks to those that can see in such as infrared or ultra violet :?:

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Re: APOD: The Eagle Nebula from Kitt Peak (2012 Apr 16)

Post by geckzilla » Tue Apr 17, 2012 5:11 pm

I could be totally wrong, here, but I'd be surprised if they can see any details in the sky at all. The compound eyes of insects are designed for terrestrial needs such as detecting motion or spotting flowers, not dim celestial objects. However, there's still a somewhat mysterious way that some animals manage to traverse vast distances and end up at precisely the right spot to procreate at. It's been suggested that they could navigate through astronomical means.
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Re: APOD: The Eagle Nebula from Kitt Peak (2012 Apr 16)

Post by Chris Peterson » Tue Apr 17, 2012 5:18 pm

geckzilla wrote:I could be totally wrong, here, but I'd be surprised if they can see any details in the sky at all. The compound eyes of insects are designed for terrestrial needs such as detecting motion or spotting flowers, not dim celestial objects. However, there's still a somewhat mysterious way that some animals manage to traverse vast distances and end up at precisely the right spot to procreate at. It's been suggested that they could navigate through astronomical means.
It's well known that moths and other nocturnal insects use the Moon, and possibly sky polarization, for navigational purposes.
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geckzilla
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Re: APOD: The Eagle Nebula from Kitt Peak (2012 Apr 16)

Post by geckzilla » Tue Apr 17, 2012 5:21 pm

Hence the reason city lights confuse the crap out of them. The moon is hardly a dim celestial object, though. :)
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Re: APOD: The Eagle Nebula from Kitt Peak (2012 Apr 16)

Post by neufer » Tue Apr 17, 2012 5:39 pm

geckzilla wrote:
There's still a somewhat mysterious way that some animals manage to traverse vast distances and end up at precisely the right spot to procreate at. It's been suggested that they could navigate through astronomical means.
http://en.wikipedia.org/wiki/Animal_navigation wrote:
<<Warblers placed in a planetarium showing the night sky oriented themselves towards the south; when the planetarium sky was then very slowly rotated, the birds maintained their orientation with respect to the displayed stars. Lockley observes that to navigate by the stars, birds would need both a "sextant and chronometer": a built-in ability to read patterns of stars and to navigate by them, which also requires an accurate time-of-day clock.>>
Art Neuendorffer

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GPS neurons

Post by neufer » Fri Apr 27, 2012 4:51 pm

geckzilla wrote:
There's still a somewhat mysterious way that some animals manage to traverse vast distances and end up at precisely the right spot to procreate at. It's been suggested that they could navigate through astronomical means.
http://www.bbc.co.uk/news/science-environment-17855194 wrote:
Magnetic fields light up 'GPS neurons', scientists say
By Jason Palmer Science and technology reporter, BBC News, 27 April 2012

<<Researchers have spotted a group of 53 cells within pigeons' brains that respond to the direction and strength of the Earth's magnetic field. These new "GPS neurons" seem to show how magnetic information is represented in birds' brains. However, the study reported by Science leaves open the question of how they actually sense the magnetic field.

David Dickman of the Baylor College of Medicine in the US set up an experiment in which pigeons were held in place, while the magnetic field around them was varied in its strength and direction. Prof Dickman and his colleague Le-Qing Wu believed that the 53 neurons were candidates for sensors, so they measured the electrical signals from each one as the field was changed.

Every neuron had its own characteristic response to the magnetic field, with each giving a sort of 3-D compass reading along the familiar north-south directions as well as pointing directly upward or downward. In life, this could help the bird determine not only its heading just as a compass does, but would also reveal its approximate position. Each cell also showed a sensitivity to field strength, with the maximum sensitivity corresponding to the strength of the Earth's natural field. And just like a compass, the neurons had opposite responses to different field "polarity" - the magnetic north and south of a field, which surprised the researchers most of all. "People had reported in the past, in a 1972 paper in Science, establishing that birds do not seem to respond to the polarity of the magnetic field, yet here we have neurons that are in fact doing that," Prof Dickman told BBC News. "That's one of the beautiful aspects of what we've identified, because it shows how single brain cells can record multiple properties or complex qualities in a simple way."

Several hypotheses hold that birds' magnetic navigation arises in cells that contain tiny chunks of metal in their noses or beaks, or possibly in an inner ear organ. However, the most widely held among them was thrown into question recently when researchers found that purported compass cells in pigeon beaks were in fact a type of white blood cell.

Another theory suggests that a magnetic sense may come about in receptors in birds' eyes. When exposed to light, the theory says, molecules called cryptochromes undergo a fleeting change in their atomic makeup whose length depends on their alignment with a field. The new work throws this latter possibility into question, as it would work equally well with a north- or south-pointing field. Asked what an outsider should think, given that the recent results conflict with the two most plausible explanations for birds' remarkable navigation abilities, Prof Dickman said "be puzzled, because I am. We're leaning toward a third receptor in the inner ear, and we're doing experiments to try to determine whether it is in fact a receptor or not."

Henrik Mouritsen of the University of Oldenburg in Germany regards the current results with caution. "[Magnetism-sensitive neurons] must be in the brain in several places... and maybe Dr Dickman has found them. If he has, it's a very, very important finding, but only time will tell," he told BBC News. "There have been lots of claims of something similar to this, and so far every one has turned out to not be independently reproducible."

Both researchers concede that more than one mechanism may be at work in bird navigation - in their eyes, beaks or ears - and Prof Dickman said he is looking forward to getting to the bottom of it. "That's what makes this whole field exciting, because there are these competing ideas out there and now, since we've discovered regions in the brain that are actually responding to the magnetic field, it intensifies our search for the receptor and how it might work.">>
Art Neuendorffer