APOD: At the Core of NGC 6752 (2012 Feb 10)

[Donnageddon]

I am so used to seeing fuzzy red blobs in deep space images of galaxies that formed not long after the Big Bang, that I never thought our own galaxy was formed only ~500 million after the creation of the universe.

Probably, all galaxies formed in the first billion years or so of the Universe- although they continued to evolve long after that (and continue to do so now).

Thanks, Chris, I did not know that. Then with the ongoing acts of merging galaxies, would it be true that the number of galaxies in the universe is diminishing?

[Chris Peterson]

Thanks, Chris, I did not know that. Then with the ongoing acts of merging galaxies, would it be true that the number of galaxies in the universe is diminishing?

Probably, although a merger can potentially produce more galaxies than were there to begin with. But I think that in the long run, mergers result in a lot more consolidation than fragmentation.

[stelei]

Yes I was ging to ask the same question as Fossilman. In this photo as in many other photos of starfields there seen to be too many short strings of stars than I would expect to see in a random distribution. Is something going on here apart from my uninformed ideas about randomness?

Hello,

It's important to realize that randomness does not produce uniformity, but... well, randomness. As such, a random distribution can contain features that *appear* non-random to our eyes, like strings of stars. There is a good post explaining this on the blog of Bill the Lizard, among others, in the entry called "How do you test a random number generator?" (http://www.billthelizard.com/2009/05/ho ... rator.html)
Other possible factors to keep in mind are that the human mind is exceptionally good at seeing patterns even where no meaningful patterns exist (after all, we owe our constellations to pareidolia ), and that the distribution of stars may not actually be random either. Stars form from dense clouds of gas which have a finite span, so it's possible that one long cloud might make several stars at the same time, which would then appear as a "string" to us. Finally, on flat 2D pictures we have no idea of the actual 3D distribution of the stars in a "string". For all we know they may be hundreds of light-years apart and just appear perfectly aligned from our point of view.

[Baldwin504]

If one could look into the maw of a worm hole, what would it look like?

Could it possibly look like NGC 6752?

Is it not possible that looking into some form of tubular phenomenon, perhaps not a worm hole, but a variation on the theme of an Einstein bridge/worm hole/star tunnel, might it not look like this?

Or would there be some other visible aspect apparent like gravitational lensing performs?

[bactame]

I see strings of stars throughout the cluster. Has anyone ever commented on this or am I just having a post-60's flashback ?

I agree that images of clusters and Einstein Cross types of images often contain strings of stars in short segments that have been mentioned above. Indeed, almost all the constellations suffer from this defect of easy recognition. However, to say the defect is in the beholder may well be defective on a higher plane. Sister stars do form in compact regions of space and they generally are similar in spectral type and luminosity since they are sub-dividing the same cloud of gas and dust. Considering that the stars we see in NGC 6752 are generally close to one another and this helps us find blue stragglers therein then it follows that these short line segments are actual lines of stars. We have no idea at this time how the orientation of NGC 6752 contributes one collection of line segments while another viewing angle might show another collection of line segments.

[orin stepanek]

Yes, when I think of a horse's black hole (which is not too often) I usually think of the other end.

If there is stuff coming out of it, wouldn't that be a white hole?

And wouldn't a wormhole be a bridge between a black hole (entrance) and a white hole (exit)?

About the only thing I worry about what comes out of a horse's patootie is to be careful not to step in it.

[TNT]

What if a black hole becomes a white hole? Then the black hole obviously ate too much. Compare that with a horse and sugar cubes. Not pretty at all.

[Chris Peterson]

Is it not possible that looking into some form of tubular phenomenon, perhaps not a worm hole, but a variation on the theme of an Einstein bridge/worm hole/star tunnel, might it not look like this?

You'd need to be more clear what you mean by a "tubular phenomenon". If wormholes exist, they don't look like anything, since they start on the other side of a black hole's event horizon. Gravitational lensing effects don't produce point sources- they act like lenses that are strongest along the optical axis, and weakest at the edges, just the opposite of conventional imaging optics.

[Diana]

Hello:

Has anyone else noticed (in the large view) the figure 8 around one of the stars near the center at about 8 O'clock? It appears to not be from the photo spikes that are emminating from most of the very bright stars. It looks blue/violet to me. Does this show up in other photos with different filters?

Thanks,
Diana

[APOD Is Cool]

Wikipedia says a wormhole looks like this: http://en.wikipedia.org/wiki/File:Loren ... rmhole.jpg
and looking into the end of one is like this: http://en.wikipedia.org/wiki/File:FY221c15.png
and a black hole or kugelblitz looks like this: http://en.wikipedia.org/wiki/File:BlackHole.jpg
Fun with Photoshop!

[Diana's Fan]

Hello:

Has anyone else noticed (in the large view) the figure 8 around one of the stars near the center at about 8 O'clock? It appears to not be from the photo spikes that are emminating from most of the very bright stars. It looks blue/violet to me. Does this show up in other photos with different filters?

Thanks,
Diana

Yes! I see it, too. Good eye! What do you suppose it is, an optics artifact of some sort? What can do that?

[Boomer12k]

What is the radiation like in a cluster like that? If there was an Earth-like planet there, at the same distance from a Sun-like star, would there be life? Would the radiation kill bacteria? It is not like there is just one star to illuminate the sky. How bright would the sky be?

:---[===] *

[Boomer12k]

This is a random TANGENT function I did on the old C64. I inserted a spinning view as it placed the dots. I was trying to make "galaxy" like patterns. But it shows that randomness can make the same strings and loops and circles as in the Cluster....
It did not matter what permutations I applied in the calculations, I got very similar results.

:---[===] *

[Ann]

Hello:

Has anyone else noticed (in the large view) the figure 8 around one of the stars near the center at about 8 O'clock? It appears to not be from the photo spikes that are emminating from most of the very bright stars. It looks blue/violet to me. Does this show up in other photos with different filters?

Thanks,
Diana

Good catch, Diana.

As a color freak I need to point out that although the figure eight (which to me looks more like two large bubbles coming out on opposite sides of the star) looks blue in this image, no blue light has been detected. The filters used to make this image were infrared, yellow-orange and yellow-green. The image taken through the yellow-green filter was mapped as blue. What we see here is two large bubbles that have been detected by the yellow-green filter, but not by the yellow-orange filter or the infrared one.

So what color are the bubbles "really"? We can't know if they emit most strongly in the yellow-green part of the spectrum or in some other part of the spectrum that was not detected by the filters used. It could be that the bubbles are dominated by the most common spectral lines found in nebulae, namely hydrogen alpha at about 656 nm and hydrogen beta at 486 nm.

MInkowski's Butterfly by Hubble.

What caused those bubbles? Since they definitely seem to be centered on the star, we must assume that they were blown by the star.

Given the fact that a Milky Way globular cluster is certainly old enough to have produced planetary nebulae and white dwarfs, I wonder if the bubbles here mean that the star is in some sort of pre-planetary nebula stage. At least the shape of the bubbles are vaguely similar to the planetary nebula you can see here, Minkowski's Butterfly.

Or else, who knows, something happened in this very crowded environment which made the star suffer a case of hiccups.

Ann

[Diana]

Hello;
**blush** I have a fan. : )

Thank you very much for responding in your detailed style Ann.

I knew they color was not 'real,' but the structure really seamed out of place. It is very cool that this doesn't show up in one filter when it does in another. Do you know if one of the radio wave or x-ray type of telescopes have ever been aimed toward this area and mapped it?

Take care,
Diana

[Ann]

Diana wrote:

Do you know if one of the radio wave or x-ray type of telescopes have ever been aimed toward this area and mapped it?

I searched for images of NGC 6752 and found some that I find interesting.

You can find two RGB images of NGC 6752 here and here. (RGB images are made by using red, green and blue filters, which produce colors similar to what the human eye would see.) Note that the bright blue star is a foreground star.

Note, too, that the blue foreground star isn't found in the same location in both images, meaning the orientation of the two pictures is not the same. That causes problems when you are looking for a specific star in a globular cluster..

An ultraviolet image of NGC 6752 can be found here. An X-ray image of NGC 6752 by the Chandra telescope can be found here.

As for any infrared searches of NGC 6752, the only thing I could find was this. It is a paper written by astronomers who have used the Spitzer Space Telescope to search for dust in globular clusters, including NGC 6752. Apparently they didn't find any, at least not in NGC 6752.

My general impression is that the structure you detected in yesterday's APOD hasn't been seen or described before.

Ann

[rstevenson]

I tried to isolate and emphasize that area of the image so we could see a little better what the figure eight might be. Here it is, not in anything like "real" colour, but at least more visible now. (I have no opinion as to what it is but I can suggest a name: Diana's Bowtie.)

Rob

[lordcat]

If you zoom in real close to the very bottem center of this image and look slightly to the left you will see a bright red star. This means it is shining brightly in the infrared. Maybe a brown dwarf or a planetary nebula?

[Chris Peterson]

Has anyone else noticed (in the large view) the figure 8 around one of the stars near the center at about 8 O'clock? It appears to not be from the photo spikes that are emminating from most of the very bright stars. It looks blue/violet to me. Does this show up in other photos with different filters?

I believe this is an artifact- it looks like a caustic, a type of internal reflection. The reason I suspect it is not a real structure is the color: the filters used for this image don't really allow for a blue object to exist. Both the green and blue channels are from filters with nearly the same bandpass (450-750 for the green, 450-625 for the blue- both filters are "visual filters" designed to give the camera a similar sensitivity to our eyes). So nothing can be captured in the blue channel that isn't also captured in the green, which means that any real object emitting in that range will show as a cyan color in the image, not deep blue. The only other obvious deep blue pixels are in diffraction spikes from the 555W channel. Since the figure-8 appears pure blue, it is probably also an artifact.

[geckzilla]

There are also two larger, fainter figure 8's at around the 5 o'clock position. I easily spotted them by looking at only the blue channel of the image in Photoshop, which I have included with the figures circled below.
(decided not to put the image itself in the thread since it's a fairly large download)
http://www.geckzilla.com/apod/figure8s.jpg

edit: Spotted a 4th one that goes off the lower right edge of the image after posting the picture. See if you can spot it.

[Beyond]

Artifacts, Artifacts, everywhere an Artifact. How does he manage to Quote just about everything?

[Chris Peterson]

The filters used to make this image were infrared, yellow-orange and yellow-green. The image taken through the yellow-green filter was mapped as blue. What we see here is two large bubbles that have been detected by the yellow-green filter, but not by the yellow-orange filter or the infrared one.

Don't get to focused on the names of the filters, because they only provide a little information about the actual bandpasses. The three filters used here were F555W, which is a wideband visual filter (a Johnson V photometric filter), designed to give the camera a similar sensitivity curve to the human eye, F606W, another wideband visual filter, and F814W, a broad near-IR filter. To our eyes, the F555W ("blue") filter will look like a low saturation green, the F606W filter ("green") will look nearly clear, and the F814W filter will be opaque.

Trying to figure out the colors of the objects by thinking of these filters as having colors of their own will clearly fail. The IR channel is isolated from the other two (that is, there is almost no overlap), and the blue channel is entirely contained inside the green channel. With these filters, no light source can produce a purely blue pixel in the final image- any photon recorded as "blue" through the 555W filter will generate just as much signal in the "green" 606W channel. (The spectrum strip above the chart is designed to give the best possible visual representation of color vs wavelength for a well calibrated RGB monitor.)

[alter-ego]

Has anyone else noticed (in the large view) the figure 8 around one of the stars near the center at about 8 O'clock? It appears to not be from the photo spikes that are emminating from most of the very bright stars. It looks blue/violet to me. Does this show up in other photos with different filters?

I believe this is an artifact- it looks like a caustic, a type of internal reflection. The reason I suspect it is not a real structure is the color: the filters used for this image don't really allow for a blue object to exist. Both the green and blue channels are from filters with nearly the same bandpass (450-750 for the green, 450-625 for the blue- both filters are "visual filters" designed to give the camera a similar sensitivity to our eyes). So nothing can be captured in the blue channel that isn't also captured in the green, which means that any real object emitting in that range will show as a cyan color in the image, not deep blue. The only other obvious deep blue pixels are in diffraction spikes from the 555W channel. Since the figure-8 appears pure blue, it is probably also an artifact.

There are also two larger, fainter figure 8's at around the 5 o'clock position. I easily spotted them by looking at only the blue channel of the image in Photoshop, which I have included with the figures circled below.
(decided not to put the image itself in the thread since it's a fairly large download)
http://www.geckzilla.com/apod/figure8s.jpg

edit: Spotted a 4th one that goes off the lower right edge of the image after posting the picture. See if you can spot it.

I think I know the culprit which is producing the features which I too am convinced are optical artifacts.
Last night I believe I found the answer. Like geckzilla, I found all four the features, three of which do appear to be 8-shaped and I also found a good candidate source star. I thought this discussion might continue today , so here is my view.

Not mentioned so far is one suspicious clue which supports an extraneous source for an internal reflection: All the figure 8's are aligned the same way. Looking at other 6752 pictures, I identified the APOD star field and quickly discovered that the figure 8's are all wistfully pointing to a "bright" 7.6 magnitude star (HIP 94198 / HD177999) located ≈2.6' out of the FoV. One reference I checked lists the star having a B-V = -0.03 which I believe fits within Chris's spectral expectations. I believe this star is the light source for those figure 8 artifacts.

[Ann]

The filters used to make this image were infrared, yellow-orange and yellow-green. The image taken through the yellow-green filter was mapped as blue. What we see here is two large bubbles that have been detected by the yellow-green filter, but not by the yellow-orange filter or the infrared one.

Don't get to focused on the names of the filters, because they only provide a little information about the actual bandpasses. The three filters used here were F555W, which is a wideband visual filter (a Johnson V photometric filter), designed to give the camera a similar sensitivity curve to the human eye, F606W, another wideband visual filter, and F814W, a broad near-IR filter. To our eyes, the F555W ("blue") filter will look like a low saturation green, the F606W filter ("green") will look nearly clear, and the F814W filter will be opaque.

filters.jpg

Trying to figure out the colors of the objects by thinking of these filters as having colors of their own will clearly fail. The IR channel is isolated from the other two (that is, there is almost no overlap), and the blue channel is entirely contained inside the green channel. With these filters, no light source can produce a purely blue pixel in the final image- any photon recorded as "blue" through the 555W filter will generate just as much signal in the "green" 606W channel. (The spectrum strip above the chart is designed to give the best possible visual representation of color vs wavelength for a well calibrated RGB monitor.)

Chris, can you explain the point of having a "blue" filter which is entirely contained inside a "green" or clear filter?

Ann

[Ann]

alter-ego, that's an interesting explanation. There is indeed a relatively bright blue foreground star which is seen in the line of sight of this cluster.

Ann