APOD: Barred Spiral Galaxy NGC 1300 (2016 Jan 09)

[rstevenson]

Trying to see the full image, I got...

The image “http://imgsrc.hubblesite.org/hu/db/imag ... ll_jpg.jpg” cannot be displayed because it contains errors.

I was getting that last night, but I just tried it and was able to load it with no problems. Maybe your browser is running out of available memory. Try downloading the image and opening it with another image viewer.

As far as I know, my browser (latest Firefox) has access to as much of the system memory (8GB in total) as it needs, whenever it needs it. And being a knowledgeable computer user from Way Back, I did try to download the image without viewing it in the browser, but got the same error code. At any rate, the image is now viewable in the usual way.

Rob

[Chris Peterson]

A couple of points. First, a slightly pedantic one- all closed orbits are elliptical (including perfectly circular ones). What you're discussing is eccentricity. Second, I'm doubtful that the stars, particularly in the center of a galaxy, have very eccentric orbits. There are dynamical mechanisms that work to circularize orbits in dense regions. Perturbations may briefly increase eccentricity, but the orbits will probably circularlize rather quickly, with a new orbital radius (or semimajor axis). The density structure that we call a bar suggests orbital resonances, but not what I'd call a synchronization of eccentricities in any way.

Scott Tremaine has proposed that the observed double nucleus could be explained if P1 is the projection of a disk of stars in an eccentric orbit around the central black hole.[76] The eccentricity is such that stars linger at the orbital apocenter, creating a concentration of stars.

I wouldn't assume we can extend a possible explanation for a double nucleus (which is of a scale orders of magnitude smaller than a bar, and possibly orders of magnitude shorter duration) to the mechanism behind a bar.

Like I said, we don't normally see dense clouds of particles maintain highly eccentric orbits. That's a dynamically unstable situation.

[Ann]

Chris wrote:
I wouldn't assume we can extend a possible explanation for a double nucleus (which is of a scale orders of magnitude smaller than a bar, and possibly orders of magnitude shorter duration) to the mechanism behind a bar.

Okay. I certainly don't know enough orbital mechanics to argue about that.

Like I said, we don't normally see dense clouds of particles maintain highly eccentric orbits. That's a dynamically unstable situation.

But bars are typically poor in gas and dust. They are usually collections of old yellow stars. Stars are point sources, more or less. Couldn't they maintain highly eccentric orbits?

And what about the dust lanes in bars? Practically all barred galaxies, at least those with any sort of significant star formation, have dust lanes along their bars. If stars in the bar follow relatively circular orbits around the center of the galaxy, they must keep crossing the dust lanes in the bar. Wouldn't that tend to destroy the dust lanes? Alternatively, wouldn't it change the orbits of the stars?

Or is it the other way round, so that the more or less circular orbits of the star in bar actually create the dust lanes in the bar, in a manner similar to the way the cumulative movement of a lot of stars in the disk of a galaxy creates a density wave that gives rise to spiral arms?

Ann

[Chris Peterson]

But bars are typically poor in gas and dust. They are usually collection of old yellow stars. Stars are point sources, more or less. Couldn't they maintain highly eccentric orbits?

Not over a long period. Dust isn't the issue, and for the most part, neither is gas. It's the stars themselves that perturb one another, and over time destroy high eccentricity orbits. And bars are found in a region of high stellar density.

And what about the dust lanes in bars? Practically all barred galaxies, at least those with any sort of significant star formation, have dust lanes along their bars. If stars in the bar follow relatively circular orbits around the center of the galaxy, they must keep crossing the dust lanes in the bar. Wouldn't that tend to destroy the dust lanes? Alternatively, wouldn't it change the orbits of the stars?

Or is it the other way round, so that the more or less circular orbits of the star in bar actually create the dust lanes in the bar, in a manner similar to the way the cumulative movement of a lot of stars in the disk of a galaxy creates a density wave that gives rise to spiral arms?

I would think that everything in circular orbits would be the most stable. Dust and gas shouldn't affect stellar orbits, but certainly, the stars could potentially redistribute gas and dust. But if everything is in circular orbits, it stays together with much less perturbation.

[Ann]

I suppose Ann is still able to be thrilled by all the blue light that is captured by black holes. It is a conceptual thing.

Click to view full size image

Visible and infrared view near newly discovered globular cluster VVV CL001.
ESO/D. Minniti/VVV Team and Digitized Sky Survey 2.
Acknowledgement: Davide De Martin

Ever since Nitpicker wrote that, I have been trying to find a picture to demonstrate that in the world of mapped color, blue can indeed be red.

Take a look at the picture at left, which shows comparison views in visible and infrared light near a newly discovered globular cluster. To me there can be no question that the infrared view (below) is not only more detailed and interesting, but it is also more beautiful. Alas, the colors are (mostly) a lie. Take a look at the brightest star at left in the infrared image. The star looks mostly white, but also faintly bluish. The same star can be identified in the visible star field. Now the infrared-bluish star is the most orange-colored of the reasonably bright stars in the visible field.

Conceivably, the infrared-bluish visibly-orange star could still be intrinsically bluish. It could be a hot star that is severely reddened by dust. Chances are that the bluish-infrared star is genuinely orange in visible light, though.

Infrared Betelgeuse.
NASA/JPL-Caltech/WISE Team.

In the world of infrared photography, a star like Betelgeuse might look brilliantly blue.

Ann

[geckzilla]

I've said it before and I'll say it again, the colors are no more a lie than one language translated to another language.

[Ann]

I've said it before and I'll say it again, the colors are no more a lie than one language translated to another language.

Translation is a hard thing.

Click to view full size image

Lingonberry jam. Source:
https://matochliteannat.wordpress.com/2 ... da-lingon/

At left you can see lingonberries, which are, or so I believe, relatively unknown in the countries in the world where very many people speak English as their first language. In Sweden, lingonberries are used to make lingonberry jam, which is eaten with many "typically Swedish" dishes, like meatballs and mashed potatoes. Anyone who lives near an IKEA department store anywhere in the world can go to their restaurant and sample their meatballs with potatoes and lingonberry jam, but for those who don't have an IKEA store nearby, the word "lingonberries" probably won't ring a bell. You could translate it by calling them cranberries, but it wouldn't be the same thing.

What I'm trying to say is that I have the greatest respect for those who try to "translate" information about other parts of the electromagnetic spectrum than the optical one into images that we can see. It's such a great thing that different telescopes have given us images of space in the X-ray, ultraviolet, infrared and radio part of the spectrum. We have learned such a tremendous amount about the universe that would have been unknown to us if we had been forced to rely on the information that is available to the rods and cones in our eyes.

Therefore it is necessary, or at least very desirable, to "translate" information about other parts of the electromagnetic spectrum into optical colors and present it as hues that we can see.

But in the end something is lost in translation. Lingonberries anyone?

Ann

[geckzilla]

Yeah, it's hard, and not everyone is going to get it, but it doesn't mean that the person who tried to describe a lingonberry to someone who's never tried one lied while doing it.