Explanation: Many spiral galaxies have bars across their centers. Even our own Milky Way Galaxy is thought to have a modest central bar. Prominently barred spiral galaxy NGC 1672, featured here, was captured in spectacular detail in an image taken by the orbiting Hubble Space Telescope. Visible are dark filamentary dust lanes, young clusters of bright blue stars, red emission nebulas of glowing hydrogen gas, a long bright bar of stars across the center, and a bright active nucleus that likely houses a supermassive black hole. Light takes about 60 million years to reach us from NGC 1672, which spans about 75,000 light years across. NGC 1672, which appears toward the constellation of the Dolphinfish (Dorado), has been studied to find out how a spiral bar contributes to star formation in a galaxy's central regions.
I don't see any "bar". What I do see is an asymmetric centre, with more bright material in the upper part (as seen in the image) of the central swirl than in the lower. What am I supposed to be looking for?
Antony Rawlinson wrote: ↑Mon Apr 06, 2020 5:33 am
I don't see any "bar". What I do see is an asymmetric centre, with more bright material in the upper part (as seen in the image) of the central swirl than in the lower. What am I supposed to be looking for?
NGC 1672 is not as strongly barred as NGC 1300 (few galaxies are). But in the Hubble image of NGC 1672 processed by Steve Cooper, which I prefer over today's APOD because of its saturated colors that help bring out different structures of the galaxy, the bar is the dark orange central part. Arguably though, you could say that the bar on the right side of the nucleus extends "almost straight out" until it meets a major arm at upper right. At the same time, this side of the bar of NGC 1672 displays strong signs of star formation in the form of many pink nebulas and blue-white star clusters.
You can see two very pronounced dark dust lanes emanating from the core of NGC 1672 and running through the orange-colored bar. Such dust lanes are typical of barred galaxies. Look closely, and you can see them in NGC 1300, too.
Most galactic bars lack star formation, but there are galactic bars that are full of young stars. Take a look at this Hubble image of NGC 1073. If you look carefully, you can see that the dust lane on the right side of the nucleus of NGC 1073 has formed many bright young clusters of blue-white stars.
To me it looks like two masses fell in towards the center, and kind of combined in the middle, creating the "bar"... these masses got kind of "fixed" at the ends of the central area, and have gravitationally merged.
Probably wrong...
A wider angle image, I think, shows disruption... from a merger... got rather "splayed out"... being thinned out, it made the inner bar more pronounced.
The main image doesn't seem to have a bar - it looks more like an ordinary spiral slightly edge on, especially when compared with other barred spirals such as NGC 1300. A thumbnail image of NGC 1672 does appear to show a slight impression of a bar, but that could be merely the slightly edge on perspective
Boomer12k wrote: ↑Mon Apr 06, 2020 6:47 am
To me it looks like two masses fell in towards the center, and kind of combined in the middle, creating the "bar"... these masses got kind of "fixed" at the ends of the central area, and have gravitationally merged.
Probably wrong...
A wider angle image, I think, shows disruption... from a merger... got rather "splayed out"... being thinned out, it made the inner bar more pronounced.
Toward the top left there is a tiny band/ arm of stars that look like they are going in the opposite direction of the normal spiral structure.Could there be some tidal dispersion going on here?
<<NGC 1672 is a barred spiral galaxy located in the constellation Dorado. NGC 1672 has a large bar which is estimated to measure around 20 kpc. It has very strong radio emissions emanating from its nucleus, bar, and the inner portion of the spiral arm region. The nucleus is Seyfert type 2 and is engulfed by a starburst region. The strongest polarized emissions come from the northeastern region which is upstream from its dust lanes. Magnetic field lines are at large angles with respect to the bar and turn smoothly to the center.
The center of the galaxy contains a high surface brightness bar, and four filament-like spiral arms extend outward from the ends of this bar. The spiral arms are asymmetric; one of the arms in the northeast part of the disk is significantly brighter than its counterpart on the other side. The spiral arms also contain numerous star formation regions, some of which may be as large as 4′′.>>
Other images of this galaxy show the bar much better than this one does. The processing of the Hubble image here appears to emphasize the dust clouds, not the brightness of the bar. A simple Google search for images of this galaxy will display many ground-based images that show the bar relatively well.
Thanks so much for the questions about the mystery of the bar in today's image. I find it hard to identify. This would be a great time to do a scroll over to outline it.
rketcham wrote: ↑Mon Apr 06, 2020 3:16 pm
Thanks so much for the questions about the mystery of the bar in today's image. I find it hard to identify. This would be a great time to do a scroll over to outline it.
Okay, this is my take on the bars of NGC 1300 and NGC 1672. Feel free to object.
NGC 1672: Barred Spiral Galaxy from Hubble
