APOD: The North America Nebula in Infrared (2011 Feb 15)

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APOD: The North America Nebula in Infrared (2011 Feb 15)

Postby APOD Robot » Tue Feb 15, 2011 5:06 am

Image The North America Nebula in Infrared

Explanation: The North America Nebula can do what most North Americans cannot -- form stars. Precisely where in the nebula these stars are forming has been mostly obscured by some of the nebula's thick dust that is opaque to visible light. However, a new view of the North America Nebula in infrared light by the orbiting Spitzer Space Telescope has peered through much of the dust and uncovered thousands of newly formed stars. Rolling your cursor over the above scientifically-colored infrared image will bring up a corresponding optical image of the same region for comparison. The new infrared image neatly captures young stars in many stages of formation, from being imbedded in dense knots of gas and dust, to being surrounded by disks and emitted jets, to being clear of their birth cocoons. The North America Nebula (NGC 7000) spans about 50 light years and lies about 1,500 light years away toward the constellation of the Swan (Cygnus). Still, of all the stars known in the North America Nebula, which massive stars emit the energetic light that gives the ionized red glow is still debated.

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Re: APOD: The North America Nebula in Infrared (2011 Feb 15)

Postby Beyond » Tue Feb 15, 2011 5:42 am

Otto Posterman wrote: The North American nebula can do what most North Americans cannot -- form stars.

That's because THEY don't have HollyWood!! So how come the Canadians have a Nebula and we don't????
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Re: APOD: The North America Nebula in Infrared (2011 Feb 15)

Postby bystander » Tue Feb 15, 2011 5:57 am

Beyond wrote:So how come the Canadians have a Nebula and we don't????

Do you think the USA is not part of North America? It's called that because it looks like the Gulf coast and the Eastern seaboard of the USA.

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Re: APOD: The North America Nebula in Infrared (2011 Feb 15)

Postby Indigo_Sunrise » Tue Feb 15, 2011 11:31 am

This is an amazing image - or should I say: these are amazing images!
I especially like the fact that as the image changes, from the infrared to the optical, some of the stars that are noticeably brighter in one image, are less so in the other image.

Excellent APOD!

8-)
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Re: APOD: The North America Nebula in Infrared (2011 Feb 15)

Postby Mr Squid » Tue Feb 15, 2011 12:42 pm

The image at the "comparison" link is very nice. I will start using that for public talks.
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Re: APOD: The North America Nebula in Infrared (2011 Feb 15)

Postby Beyond » Tue Feb 15, 2011 2:37 pm

bystander wrote:
Beyond wrote:So how come the Canadians have a Nebula and we don't????

Do you think the USA is not part of North America? It's called that because it looks like the Gulf coast and the Eastern seaboard of the USA.

viewtopic.php?f=29&t=22882

I must be mistaking the continent with the labeling of the populace.Oops :oops: In THAT case, WE do make our own Stars!! Hollywood is still a star maker,even though they don't seem to shine as bright as they used to.

The pictures that you refferenced in your 'view topic' are no longer there. Spitzer at Cal-tech has moved them, so i can't tell if it the Nebula looks like the North-American Continent or not. The Apod picture must be a too close-up view to tell. Is there another picture somewhere that shows It's shape?

Nevermind. i just found one that shows It's shape. It's just close enough shaped to get away with It's title and it might even be better than our Continent, as i didn't see any spilled oil in the Gulf region!
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Re: APOD: The North America Nebula in Infrared (2011 Feb 15)

Postby bystander » Tue Feb 15, 2011 3:12 pm

Beyond wrote:
bystander wrote: viewtopic.php?f=29&t=22882

The pictures that you refferenced in your 'view topic' are no longer there. Spitzer at Cal-tech has moved them,

This has been fixed.
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Re: APOD: The North America Nebula in Infrared (2011 Feb 15)

Postby moikey@att.net » Tue Feb 15, 2011 4:09 pm

Also; Mexico is part of the North American Continent.
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Re: APOD: The North America Nebula in Infrared (2011 Feb 15)

Postby Beyond » Tue Feb 15, 2011 4:23 pm

moikey@att.net wrote:Also; Mexico is part of the North American Continent.

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Re: APOD: The North America Nebula in Infrared (2011 Feb 15)

Postby hadashinogen3 » Tue Feb 15, 2011 4:37 pm

Are you sure both images are of the N. American nebula? Are they the same scale and orientation? I am having difficulty identifying identical objects in both. But thanks.
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Re: APOD: The North America Nebula in Infrared (2011 Feb 15)

Postby Guest » Tue Feb 15, 2011 4:51 pm

Near the left edge, just below the middle of the image, there is a star-like object that moves significantly between the two photos. Do you know what that is?
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Re: APOD: The North America Nebula in Infrared (2011 Feb 15)

Postby bystander » Tue Feb 15, 2011 5:03 pm

hadashinogen3 wrote:Are you sure both images are of the N. American nebula? Are they the same scale and orientation? I am having difficulty identifying identical objects in both. But thanks.

Yes, they are both the same area, scale and orientation. The initial image is infrared and the mouse over is visible light. Maybe this image will help:

Changing Face of the North America Nebula

This image layout reveals how the appearance of the North America nebula can change dramatically using different combinations of visible and infrared observations from the Digitized Sky Survey and NASA's Spitzer Space Telescope, respectively.

In this progression, the visible-light view (upper left) shows a striking similarity to the North America continent. The image highlights the eastern seaboard and Gulf of Mexico regions. The red region to the right is known as the "Pelican nebula," after its resemblance in visible light to a pelican.

The view at upper right includes both visible and infrared observations. The hot gas comprising the North America continent and the Pelican now takes on a vivid blue hue, while red colors display the infrared light. Inky black dust features start to glow in the infrared view.

In the bottom two images, only infrared light from Spitzer is shown -- data from the infrared array camera is on the left, and data from both the infrared array camera and the multiband imaging photometer, which sees longer wavelengths, is on the right. These pictures look different in part because infrared light can penetrate dust whereas visible light cannot. Dusty, dark clouds in the visible image become transparent in Spitzer's view. In addition, Spitzer's infrared detectors pick up the glow of dusty cocoons enveloping baby stars.

Color is used to display different parts of the spectrum in each of these images. In the visible-light view (upper right) from the Digitized Sky Survey, colors are shown in their natural blue and red hues. The combined visible/infrared image (upper left) shows visible light as blue, and infrared light as green and red. The infrared array camera (lower left) represents light with a wavelength of 3.6 microns as blue, 4.5 microns as green, 5.8 microns as orange, and 8.0 microns as red. In the final image, incorporating the multiband imaging photometer data, light with a wavelength of 3.6 microns has been color coded blue; 4.5-micron light is blue-green; 5.8-micron and 8.0-micron light are green; and 24-micron light is red.

or see this video:

Click to play embedded YouTube video.
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Re: APOD: The North America Nebula in Infrared (2011 Feb 15)

Postby bystander » Tue Feb 15, 2011 5:07 pm

Guest wrote:Near the left edge, just below the middle of the image, there is a star-like object that moves significantly between the two photos. Do you know what that is?

I think you are seeing two different objects. Objects that are bright in the visible spectrum are not necessarily bright in infrared.
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Re: APOD: The North America Nebula in Infrared (2011 Feb 15)

Postby Ann » Tue Feb 15, 2011 5:27 pm

Indigo_Sunrise wrote:This is an amazing image - or should I say: these are amazing images!
I especially like the fact that as the image changes, from the infrared to the optical, some of the stars that are noticeably brighter in one image, are less so in the other image.

Excellent APOD!

8-)


This infrared image, while remarkable and hugely interesting in many ways, doesn't do a good job of showing the bolometric (total) energy output of the stars. Of course, that isn't what it is meant to do, either. For all of that, it might be interesting to take a closer look at how the image represents the brightness of different types of stars.

Look at the visible-light image of the North America Nebula and note a reasonably bright blue star at top center or center-left. This is HD 199579, an intrinsically very, very bright and massive O-type star. In fact, its spectral type is the same as Theta-1 C Orionis, the star that is ionizing the Orion Nebula. We can be sure that the bolometric energy output of HD 199579 is at least 100,000 times that of the Sun. But because the star produces most of its energy in the ultraviolet, and because most of its visual light is blue and purple, the star is barely visible at all in infrared light. If you want to detect it at all in the infrared image, you'd better look at the visual-light image and put your finger on the screen where the star is to "mark the spot", as it were. In the infrared image this scorchingly hot mighty star all but disappears.

But take a look at the infrared image and note the apparently brightest of all blue-looking stars - that is, look at the star that is the apparently brightest of all stars in the near infrared, which is mapped as blue in this image. What star is this? Why, it's HD 199799, an M-type star, whose visible-light color is similar to that of reddish Betelgeuse. But HD 199799 is no M-type supergiant: its (uncertain) luminosity in visual light is about 200 times that of the Sun. However, because it is an M-type star, it emits most of its energy in the (near) infrared, which is why it looks so bright in the infrared image of the North America Nebula. There is no doubt that HD 199799 emits a lot more than 200 times the energy of the Sun if we take the infrared light into account. It may very well emit several thousand times the energy of our own G-type star! But even so, the bolometric, total, energy output of this M-type star is probably less than a tenth of the energy output of the hot blue O-type star. So you shouldn't use this infrared image to judge the bolometric energy output of the stars here!

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Re: APOD: The North America Nebula in Infrared (2011 Feb 15)

Postby NoelC » Tue Feb 15, 2011 9:48 pm

I find it interesting that a hotter star can appear dimmer than a cooler star in one spectrum of light, yet brighter in another.

Is it because the hotter star is actually more distant (or smaller), yet SO much brighter in the visible spectrum that it looks brighter to us here?

Put another way, imagining two stars of the same size and distance but one burning hotter than the other, wouldn't the hotter one appear as bright or brighter in IR light as the dimmer one?

As a star gets hotter, there's no shift of energy AWAY from the lower wavelengths... There's just more at higher wavelengths, right? Or am I missing something?

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Re: APOD: The North America Nebula in Infrared (2011 Feb 15)

Postby neufer » Tue Feb 15, 2011 10:44 pm

NoelC wrote:
Imagining two stars of the same size and distance but one burning hotter than the other, wouldn't the hotter one appear as bright or brighter in IR light as the dimmer one?

As a star gets hotter, there's no shift of energy AWAY from the lower wavelengths... There's just more at higher wavelengths, right? Or am I missing something?

Long Wave Radiation is, more or less, just linearly related to temperature such that a 30,000K star is only 10 times brighter in IR than a 3,000K star of the same surface area.

However, if that 3,000K star is a red giant or super-giant with 10 times the radius of the hotter star then it will have 100 times the surface area and hence end up being 10 times brighter than the hot star in the IR. The infrared picture is essentially evaluating the stars based upon their surface area while the visible picture is evaluating the stars more by their temperature and/or the amount of dust extinction.
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Re: APOD: The North America Nebula in Infrared (2011 Feb 15)

Postby NoelC » Tue Feb 15, 2011 11:28 pm

Thank you for confirming my thoughts, Art. And yes, I had neglected transparency of the medium, though in the case of the hotter visible star being brighter, that would serve to work against the difference, not increase it. However, IR penetrates the dust better, and so the cooler star that appears brighter in IR light might just be less obscured.

Shouldn't your "surface" area calculation simplify the 3 dimensional star into a 2 dimensional disk, which is essentially what we see? That's why the linear relationship between radius and brightness.

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Re: APOD: The North America Nebula in Infrared (2011 Feb 15)

Postby neufer » Wed Feb 16, 2011 3:15 am

NoelC wrote:
Shouldn't your "surface" area calculation simplify the 3 dimensional star into a 2 dimensional disk, which is essentially what we see? That's why the linear relationship between radius and brightness.

Right... "surface" area goes with the square of the scale such that in my simple example there is indeed a linear relationship between radius and brightness.

However, the really important concept here is that the infrared star images are simply dominated by the red super-giant stars thanks to their enormous "surface" areas (while star brightness in the visible is much more complex). Look at the IR stars and think "red super-giants."
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