APOD: Evaporating Blobs of the Carina Nebula (2012 Apr 23)

[APOD Robot]

Evaporating Blobs of the Carina Nebula

Explanation: No, they are not alive -- but they are dying. The unusual blobs found in the Carina nebula, some of which are seen floating on the upper right, might best be described as evaporating. Energetic light and winds from nearby stars are breaking apart the dark dust grains that make the iconic forms opaque. Ironically the blobs, otherwise known as dark molecular clouds, frequently create in their midst the very stars that later destroy them. The floating space mountains pictured above by the orbiting Hubble Space Telescope span a few light months. The Great Nebula in Carina itself spans about 30 light years, lies about 7,500 light years away, and can be seen with a small telescope toward the constellation of Keel (Carina).

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[Flase]

Is that a planetary nebula just to the left of the star near the centre, or is that just an artifact of refection in the lens?

[ritwik]

these things spans light years and lasts for billions of years,but we humans just live for 100 odd years at best..i recently lost interest in astronomy

[Flase]

But when you see there is something bigger than you, you see how petty all your little problems are. All the debts and things that have people running around with high blood pressure hurting each other are nothing really...

[jimbo48]

Is that a planetary nebula just to the left of the star near the centre, or is that just an artifact of refection in the lens?

I am wondering about that also. Sure looks like a planetary nebula. Anybody know for sure?

[orin stepanek]

Today's APOD is really nice.

[geckzilla]

Is that a planetary nebula just to the left of the star near the centre, or is that just an artifact of refection in the lens?

I am wondering about that also. Sure looks like a planetary nebula. Anybody know for sure?

It's a "ghost image"
See: http://www-int.stsci.edu/instruments/wf ... 9506_9.pdf
I'm surprised it wasn't removed.

Edit:
Also, see: http://hla.stsci.edu/cgi-bin/display?im ... d%29%20LOW
There's another faint one in WF2 (the bottom left square) and you can see more of them in WF4 (the top square) and they all emanate from the center of each square.

[Ann]

Is that a planetary nebula just to the left of the star near the centre, or is that just an artifact of refection in the lens?

My guess is that it isn't a planetary nebula.

This is a starforming region dominated by young stars. There are some extremely massive stars here, particularly Eta Carina itself, but there are other heavyweights too. They have not gone supernova yet.

A star that is massive enogh to go supernova will not leave a planetary nebula behind, but a supernova remnant along with a neutron star or a black hole. If that ring-like object is really a planetary nebula, it must have been made by a star that was considerably less massive than the dominant stars of the Carina Nebula. But the more massive a star is, the faster it will burn out and die. It the ring-like object is a planetary nebula, it must have been made by a star that was much older than the dominant stars of the Carina Nebula as well as less massive.

In short, the Carina Nebula with its bright stellar behemoths is not the place where we would expect to find many planetary nebulae. Of course we can't disregard the possibility that the object is indeed a planetary nebula and that it is a member of an older population in the Carina Nebula.

But there is another thing that seems slightly wrong to me if the ring-shaped object is a plantery , and that is the combination of its color and structure. If the object is a planetary, then the blue color almost certainly means blue-green OIII emission. However, OIII emission is chiefly found in very rarefied conditions, and that ring seems pretty "thick".

So I would guess that the ring is an artifact of some kind.

Ann

[geckzilla]

[Chris Peterson]

It's a "ghost image"
See: http://www-int.stsci.edu/instruments/wf ... 9506_9.pdf
I'm surprised it wasn't removed.

Ghost images are not removed from images used for scientific purposes, they are only removed for aesthetic reasons. Given the focus of the people who collect and do most of the processing on HST data, it's not surprising that artifacts like this occasionally survive.

Ghost images caused by internal reflections are not unique to the HST, of course. We see them on many APODs, from many sources (and they often provoke questions). On images made with reflecting telescopes, they usually present as donuts, because of the circular central obstruction in the aperture. On images made with refracting telescopes, which have no obstruction, they are usually just round blobs. Either way, the resemblance to a planetary nebula is common. With refracting optics, ghost images are commonly blue or blue-green, because that color is selectively reflected by "anti-reflection" coatings. This color is often deceptively similar to the color of OIII emitting nebulas. With reflecting optics, which produce more accurate color, ghosts are usually the same color as the light source (usually a star) that creates them. In any case, the object that is being reflected can be (and often is) outside the field of view of the camera, which further confuses things.

As Ann pointed out, these sort of regions may not contain the kind of stars that produce planetary nebulas- they simply aren't old enough. In addition, planetary nebulas are very tenuous, which means they are fragile. If a lower mass star happened to be passing through an active star forming region, and expelled its outer layers to produce a planetary nebula, it's likely that the violent stellar winds in the region would rapidly dissipate that nebula. So rather than a nice ring, we'd probably see- at most- a faint amorphous blob, not something highly structured like a ring or sphere.

[geckzilla]

Because these images are produced mainly for aesthetic reasons, it surprises me that something distracting like a ghost image would be left in.

[Chris Peterson]

Because these images are produced mainly for aesthetic reasons, it surprises me that something distracting like a ghost image would be left in.

Understood. My point was simply that the people actually processing the images aren't primarily aesthetic imagers, so they're perhaps less practiced at producing those kinds of images than many amateur imagers. So sometimes artifacts remain. There are other artifacts in this image, as well. It also depends on the imaging philosophy of the processor. Some artifacts can be removed without significantly compromising the integrity of the underlying image. The donut can't- it completely obscures the underlying region, so removing it would require actually making up data to cover it, either by painting or cloning (which we also see occasionally in APODs, and which also produces comments and complaints... you just can't win <g>). Personally, I leave such artifacts in my images, even when the intent is aesthetic. I know other imagers who feel the same, and I'd expect to find quite a few working at the organization that published this image.

[geckzilla]

Cloning (and Healing, if you have a recent enough version of Photoshop) can be done well enough to not cause questions to arise. I know there's no absolute way to look at it and on the one hand you are, in a way, corrupting the data every time you edit some bit away... but I put this kind of anomaly in the same category as charge bleeds. Easy enough to remove without it being apparent that it was done and distracting enough to warrant removal. However, I'm a complete newbie at this, so I have no authority on the matter. I guess I should have stated that in the beginning. I think I'll go to their Facebook page and ask them. Maybe I'll get a reply!

[emc]

Beautiful! Quite a composition! Quite an imagination ignitor!
i.e., Brings Dali to mind.

[Chris Peterson]

Cloning (and Healing, if you have a recent enough version of Photoshop) can be done well enough to not cause questions to arise. I know there's no absolute way to look at it and on the one hand you are, in a way, corrupting the data every time you edit some bit away... but I put this kind of anomaly in the same category as charge bleeds. Easy enough to remove without it being apparent that it was done and distracting enough to warrant removal.

I also never remove blooming spikes, even from aesthetic images, unless I can do so using another frame where they run in a different direction with respect to the image. My imaging philosophy is that artifacts are better than synthesized data, no matter how well it's done. As far as images with aesthetic intent, I have absolutely no problem with people who choose to use tools like cloning, and I'm not saying there's anything wrong with that (as long as the data isn't intended for scientific analysis, and there's no attempt at deception, of course). But there are plenty of imagers who operate as I do, especially those from scientific backgrounds, which is why I offered this as a possible explanation for why the artifact remained (simple oversight being another).

[geckzilla]

I did get a reply! A kind of amusing one, at that.

Hi Judy- The little donut at 9:30 and the blue one closer into the halo at about 5:30 are definitely ghosts, signature artifacts from WFPC2. Old rumor has it that at one early AAS meeting after the installation of that camera, a data analyst had the sad job of walking up to an astronomer at an AAS poster who thought these little guys were polar ring galaxies, to let said astronomer know that they were mirror ghosts. Hubble Heritage and STScI remove these. I have asked ESA Hubble to comment on their artifact removal rules.

Best, Lisa Frattare STScI/Hubble Heritage

Reason for leaving the errant donut is on its way (I think).

[geckzilla]

I also never remove blooming spikes, even from aesthetic images . . .

Oh yeah, the blooming spikes I think are aesthetic (then again, I also like "dragon's breath" and that always gets removed), as well as useful for interpreting the image. What I was mentioning earlier are the severe ones that happen quite often in Hubble's ACS images. More about them here: http://hla.stsci.edu/hlaisr0801.pdf
And even a more specific detailing on the removal of them on page 102 of the PDF version of this paper: http://arxiv.org/abs/astro-ph/0412138

[Chris Peterson]

I did get a reply! A kind of amusing one, at that.

Hi Judy- The little donut at 9:30 and the blue one closer into the halo at about 5:30 are definitely ghosts, signature artifacts from WFPC2. Old rumor has it that at one early AAS meeting after the installation of that camera, a data analyst had the sad job of walking up to an astronomer at an AAS poster who thought these little guys were polar ring galaxies, to let said astronomer know that they were mirror ghosts. Hubble Heritage and STScI remove these. I have asked ESA Hubble to comment on their artifact removal rules.

Best, Lisa Frattare STScI/Hubble Heritage

Reason for leaving the errant donut is on its way (I think).

Interesting... not the explanation, but the fact that these organizations apparently have standardized policies for how to deal with visible artifacts. Sort of the scientific imager's version of a journalist's stylebook, I guess.

[Chris Peterson]

I also never remove blooming spikes, even from aesthetic images . . .

Oh yeah, the blooming spikes I think are aesthetic (then again, I also like "dragon's breath" and that always gets removed), as well as useful for interpreting the image. What I was mentioning earlier are the severe ones that happen quite often in Hubble's ACS images. More about them here: http://hla.stsci.edu/hlaisr0801.pdf
And even a more specific detailing on the removal of them on page 102 of the PDF version of this paper: http://arxiv.org/abs/astro-ph/0412138

I don't like blooming spikes. When I'm shooting an image with the intent of producing something aesthetic, I try to eliminate them at the source, by shooting shorter subframes (at the expense of some added noise). I just prefer blooming spikes to faking data in order to remove them. Again, just a personal philosophical choice.

[geckzilla]

Well, gigantic ones aren't all that great, but a little bit of spikes are nice... then again it's my fault for not having my own telescope to look through because when I see stars without spikes they don't look "right" to me. Strangely, I am pretty sure I have seen images where the processor added spikes in where I am almost certain they weren't there to begin with. Now that's crossing a line for me.

[Chris Peterson]

Well, gigantic ones aren't all that great, but a little bit of spikes are nice... then again it's my fault for not having my own telescope to look through because when I see stars without spikes they don't look "right" to me. Strangely, I am pretty sure I have seen images where the processor added spikes in where I am almost certain they weren't there to begin with. Now that's crossing a line for me.

You're right. Some imagers with refractors (which don't produce diffraction spikes) like the aesthetics of the spikes, and add them- either physically by stringing wire crosshairs across the aperture, or by some sort of image processing trick (there are star filter plugins for Photoshop). I've never heard of anybody deliberately adding blooming spikes, though!

[geckzilla]

Yikes, I meant diffraction spikes. I think our whole conversation is messed up because I've been dumb.

[Chris Peterson]

Yikes, I meant diffraction spikes. I think our whole conversation is messed up because I've been dumb.

Confused. Never dumb.

[geckzilla]

Whichever word you use to describe it, a derp is a derp.


Actually, what's the difference between a blooming spike and a diffraction spike? Are the blooming spikes the lesser spikes seen between diffraction spikes?

Edit: Nevermind, blooming spike = charge bleed

[BeautifulUniverse]

Isn't it interesting how "objective" astronomers and scientists will project their own fundamental worldviews to how they describe space phenomena? In the above picture, dust and gas (fertile cosmic soil) becomes refined due to natural processes to ignite a star, which then continues its evolution. But the astronomer implies, darkly (without realizing it), that the dust bodies are living beings being killed by the stars they create.

This is how it is in most of astronomy ... from galaxies cannibalizing one another (instead of beautifully merging), black holes consuming voraciously (black despite they are the brightest phenomenon in the universe, and destructive despite that they unify the whole galaxy together), to supernova being stars 'death-throws', instead of just another evolutionary phase ... evolution which creates all life ...

Such astronomers project the idea that death, destruction, and competition are the fundamental principles underlying all of Nature ... ignoring the harmony, cooperation, and inter-dependence that support universal evolution ...