Starship Asterisk*

bmesser wrote:A really great image, but you've used the exact same image before and it's a big universe. Any chance of seeing NGC 1299 or 1301? Perhaps they aren't quite as impressive as NGC 1300 but at least they would be new.

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rstevenson wrote:Trying to see the full image, I got...

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Rob

https://en.wikipedia.org/wiki/Barred_spiral_galaxy wrote:

[b]M 83 (the Southern Pinwheel Galaxy) composite of the [color=#FF0000]radio light (neutral hydrogen in red)[/color] with [color=#0000FF]ultraviolet light (hot newly-formed stars)[/color]. Image credit: NASA / JPL-Caltech / VLA / MPIA.[/b]

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<<Up to two-thirds of all spiral galaxies contain a bar. The current hypothesis is that the bar structure acts as a type of stellar nursery, fueling star birth at their centers. The bar is thought to act as a mechanism that channels gas inwards from the spiral arms through orbital resonance, in effect funneling the flow to create new stars. This process is also thought to explain why many barred spiral galaxies have active galactic nuclei, such as that seen in the Southern Pinwheel Galaxy.

The creation of the bar is generally thought to be the result of a density wave radiating from the center of the galaxy whose effects reshape the orbits of the inner stars. This effect builds over time to stars orbiting further out, which creates a self-perpetuating bar structure.

Bars are thought to be temporary phenomena in the lives of spiral galaxies; the bar structures decay over time, transforming galaxies from barred spirals to more "regular" spiral patterns. Past a certain size the accumulated mass of the bar compromises the stability of the overall bar structure. Barred spiral galaxies with high mass accumulated in their center tend to have short, stubby bars. Since so many spiral galaxies have bar structures, it is likely that they are recurring phenomena in spiral galaxy development. The oscillating evolutionary cycle from spiral galaxy to barred spiral galaxy is thought to take on the average about two billion years.

Recent studies have confirmed the idea that bars are a sign of galaxies reaching full maturity as the "formative years" end. A team led by Kartik Sheth of the Spitzer Science Center at the California Institute of Technology in Pasadena discovered that only 20 percent of the spiral galaxies in the distant past possessed bars, compared with nearly 70 percent of their modern counterparts.>>

https://en.wikipedia.org/wiki/Mos_Eisley_Cantina wrote:
<<The Chalmun's Cantina (often called the Mos Eisley Cantina) is a fictional bar of the Star Wars universe located in the "pirate city" of Mos Eisley on the planet Tatooine. It is the haunt of freight pilots and other dangerous characters of various alien races and contains booths, a bar counter, and some free-standing tables, and sometimes a band of musicians named Figrin D'an and the Modal Nodes. The establishment is extremely rough in nature, and the clientele and the management give incidents of deadly violence no more than a moment's attention. Droids are not allowed inside; a droid detector near the front door alerts the management of any entering droid.>>

https://en.wikipedia.org/wiki/Star_Wars:_The_Force_Awakens#Cast wrote:
<<Maz Kanata: A wise and perceptive figure operating a somewhat shady cantina on the peaceful forest planet, Takodana. J.J. Abrams said Kanata has "lived over a thousand years. She's had this watering hole … and it's like another bar that you'd find in a corner of the Star Wars universe." According to Abrams, the character was based on his former high school English teacher, Rose Gilbert, who lectured at the Palisades Charter High School from 1961 to 2013. "I mentioned Rose in an early story meeting as a sort of timeless, wise figure that I'd actually known in my life.">>

Wikipedia wrote:
Past a certain size the accumulated mass of the bar compromises the stability of the overall bar structure. Barred spiral galaxies with high mass accumulated in their center tend to have short, stubby bars.

Ann wrote:
And what about the central black hole of NGC 1300?

neufer wrote:

Ann wrote:And what about the central black hole of NGC 1300?

Color Commentators aren't authorized to discuss black holes...out of their jurisdiction.

ta152h0 wrote:How can you tell the difference between blue light due to red shift or actual blue emissions ?

ta152h0 wrote:How can you tell the difference between blue light due to red shift or actual blue emissions ?

Nitpicker wrote: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.

quigley wrote:Thank you Ann and Neufer for the great explanations of the origins of galactic bars. Upon viewing this image, the first question that came to mind was, "What causes such distinctive formations to occur?" You answered that. So the spiral arms "peel" off stars from the ends of the bars over time?

Source:http: //www.astro-tom.com/technical_data/elliptical_orbits.htm

Ann wrote:I think that basically two things are happening. First and most importantly, the orbits of the stars near the center of the galaxy start following elliptical (elongated) orbits around the center of the galaxy. They then synchronize their orbits so that all or most stars in that part of the galaxy follow more or less the same elliptical orbit.

Chris Peterson wrote:

Ann wrote:I think that basically two things are happening. First and most importantly, the orbits of the stars near the center of the galaxy start following elliptical (elongated) orbits around the center of the galaxy. They then synchronize their orbits so that all or most stars in that part of the galaxy follow more or less the same elliptical orbit.

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.

Wikipedia wrote:
In 1991 Tod R. Lauer used WFPC, then on board the Hubble Space Telescope, to image M31's inner nucleus. The nucleus consists of two concentrations separated by 1.5 parsecs (4.9 ly). The brighter concentration, designated as P1, is offset from the center of the galaxy. The dimmer concentration, P2, falls at the true center of the galaxy and contains a black hole measured at 3–5 × 107 M☉ in 1993,[73] and at 1.1–2.3 × 108 M☉ in 2005.[74] The velocity dispersion of material around it is measured to be ≈ 160 km/s.[75]

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.