ngc2903 (APOD 06 July 2007)

[BMAONE23]

http://antwrp.gsfc.nasa.gov/apod/image/ ... any_lg.jpg

There is much chaos visible in the central area evident in the dramatic dust lanes near the galactic center. Looking at the patterns in the area, it appears (to my untrained eye) that there are two massive central black holes about 10,000 ly apart.

This Hubble image though is far clearer and almost seems to show an entirely different galaxy
http://antwrp.gsfc.nasa.gov/apod/ap010321.html

[Qev]

I'm curious, in the bottom-right of the full version of the current APOD image of NGC 2903, to the right of the small, bluish (what I assume to be) dwarf satellite galaxy, is that collection of reddish objects a background galaxy cluster?

[jgabany]

I'm curious, in the bottom-right of the full version of the current APOD image of NGC 2903, to the right of the small, bluish (what I assume to be) dwarf satellite galaxy, is that collection of reddish objects a background galaxy cluster?

Hello:

I went back to my original data and took a careful look at the area you mentioned and, yes, the small group of red colored objects appears to represent a distant cluster of galaxies.

Jay

[jgabany]

http://antwrp.gsfc.nasa.gov/apod/image/ ... any_lg.jpg

There is much chaos visible in the central area evident in the dramatic dust lanes near the galactic center. Looking at the patterns in the area, it appears (to my untrained eye) that there are two massive central black holes about 10,000 ly apart.

This Hubble image though is far clearer and almost seems to show an entirely different galaxy
http://antwrp.gsfc.nasa.gov/apod/ap010321.html

Hi:

About two-thirds of all spiral galaxies have a river of gas, dust and stars running through their inner most area that bridges the spiral arms located on either side. These are called barred spiral galaxies and even our Milky Way is now thought to possess one.

The bar is thought to be caused by a density wave similar to the ones that give rise to spiral arms. But, this type of density wave extends laterally from the galaxy's center. At first, the wave changes the orbits of interior stars but, over time, it affects stars farther out. As more time passes, it enlarges and creates this unusual, bright structure.

Bars cause the motions of interstellar dust clouds and a large number of stars within the galaxy to become chaotic. Collisions between the clouds become frequent and violent and this causes the clouds to move all over the galaxy's disk thus radially redistributing the gas and dust within an Island Universe.

In particular, a large quantity of gas will fall along the bar and eventually reach the galaxy's central region. This is why it is believed that bars could be an important source of material that feeds the supermassive black hole found at the heart of most galaxies.

This Island Universe has been described as a "hot-spot" galaxy which both the Hubble image you referenced and this picture display.

Your comment about the apparent differences between the two images can be explained by their variance in contrast range. The Hubble picture, for example, was produced with low levels of contrast so that the central hot spots and absorption nebulae could easily seen. This image, however, has much higher levels of contrast which helped surface its complex structure of reflection nebula and overall depth. I hope this makes sense...


Jay

[brbear1]

Wow! Today's APOD, NGC 2903, looks like one of the big lollipops you can buy at a fair.

[jimmysnyder]

It is. Jay got the picture mixed up with some snaps of a recent family outing.

[brbear1]

Sweet.

[Pete]

Hmm... I sure hope nobody mixes up the next APOD with some snaps of a recent high-res supermodel photo shoot

[AZJames]

NGC 2903 is an extraordinarily beautiful object. I take it that the 'bar' in this particular barred- spiral is unusual in having many star-forming regions, rather than being comprised of mainly old stars.

Is it possible that the core of NGC 2903 may have been infused with gas and dust through a galactic collision?

I'm just an interested tourist here, so my knowledge is limited. But I'm curious about the many stellar-like objects surrounding the galaxy. I see just 6 objects in the photo with diffraction streaks. Are all the rest either globular clusters or distant galaxys?

Also, why is it that only 'near' stars (in our galaxy) have the diffraction pattern? Is it because only they are point sources of light?

[rigelan]

I think the diffraction streaks arise from the amount of light or brightness of the object. The closer it is, the brighter it is (on average ) and the larger the diffraction spikes.

[jgabany]

Hello AZ:

Please see my responses interspaced between your original text, below:

NGC 2903 is an extraordinarily beautiful object. I take it that the 'bar' in this particular barred- spiral is unusual in having many star-forming regions, rather than being comprised of mainly old stars.

Is it possible that the core of NGC 2903 may have been infused with gas and dust through a galactic collision?

RJG>> Certainly, many astronomers now believe that galaxies evolve by capturing, disrupting and accreting smaller Island Universes that wander too close and become locked into their gravitational embrace. However, there is nothing in this image or others that I have studied, nor in articles and papers that I have read, which indicates a recent encounter between NGC 2903 and another galaxy. However, I have read several general descriptions about barred spiral galaxies that almost perfectly describe what is seen in this picture:

"Bars affect galaxy evolution. Introducing a bar in a spiral disk will result in some dramatic changes for the host galaxy. When the bar is formed, motions of a large fraction of the stars in the galaxy become chaotic. For the interstellar gas clouds, these chaotic motions are also induced. Collisions between the clouds in the system disk become frequent and violent. Models show that the clouds then start moving all over the galaxy disk: there is a radial redistribution of the gas. In particular, a large quantity of gas will fall along the bar and might eventually reach the galaxy center. This is why it is believe that bars could be an important factor in feeding up massive black holes with interstellar material in the center of numerous galaxies."

See http://www.cfht.hawaii.edu/Science/Astr ... 50500.html for the full text.

I'm just an interested tourist here, so my knowledge is limited. But I'm curious about the many stellar-like objects surrounding the galaxy. I see just 6 objects in the photo with diffraction streaks. Are all the rest either globular clusters or distant galaxys?

RJG>> Most of the objects in this image that have a stellar appearance are foreground stars that form a curtain through which me must gaze when looking outward into intergalactic space. Obviously, the objects with diffraction spikes are actually much, much closer to us and are located in our own Milky Way. Many of the other, small, bright, round objects also fit this description.

However, many of the bright points of light seen along the face of the galaxy are actually bright star clusters which cannot be resolved into their individual constituents due to the galaxy's extreme distance from Earth and the limited resolving capability of my 20-inch telescope. If you look at the largest image, by clicking on the APOD picture, you will notice lots of very dim, relatively colorless points that represent galaxies that are much farther in the distance than NGC 2903. There are also some objects that have elongated and spiral shapes. These, too, are other galaxies that were caught by our line of site.

Also, why is it that only 'near' stars (in our galaxy) have the diffraction pattern? Is it because only they are point sources of light?

RJG>> Diffraction spikes are an optical artifact and are proportional to the brilliance of the star that causes them. However, only a handful of stars had sufficient brightness to cause them in this particular image.

I hope my responses make sense. If not, please let me know and I will try to re-explain in more detail.


Jay

[BMAONE23]

wrong Heavenly Body

[BMAONE23]

http://antwrp.gsfc.nasa.gov/apod/image/ ... any_lg.jpg

There is much chaos visible in the central area evident in the dramatic dust lanes near the galactic center. Looking at the patterns in the area, it appears (to my untrained eye) that there are two massive central black holes about 10,000 ly apart.

This Hubble image though is far clearer and almost seems to show an entirely different galaxy
http://antwrp.gsfc.nasa.gov/apod/ap010321.html

This is also an interesting image from APOD of 6 different galaxies. NGC 2903 is in the lower right corner. http://antwrp.gsfc.nasa.gov/apod/ap990322.html
Could all those bright central light sources be black holes? If they are ultra dense matter, might that also explain the chaotic distribution of the central dust?

[jgabany]

Hello BMAONE23:

I have viewed the image that you referenced in your post and did a little bit of digging so that I could respond correctly.

In the case of NGC 5669, specifically, the multiple bright areas you see near this galaxy's center are not evidence of multiple black holes. Although they appear quite tiny in the photograph, they are unbelievably massive and enormous areas of intense stellar formation. Huge quantities of dust is being channeled into the galaxy's central region by the bar structure and as the material coalesces under gravity, stars are being born at a furious pace. This galaxy has been described as having numerous hot spots and that label came, predominantly, from our view of these bright central star forming areas.

Although there is little doubt that this galaxy has a supermassive black hole purring at its center (because most astronomers, now, are convinced that almost every galaxy in the Universe possesses one), the chaotic activity that we are witnessing at the center of NGC 5669 is not being caused by its presence.

Also, one other thing to note, galaxies with more than one supermassive black hole are thought to be the result of a prior galactic merger between one or more similarly sized Island Universes. And while NGC 5669, most likely, has accrued smaller galaxies that wandered too close in the distant past, there is no current evidence to suggest that this happened during a relatively recent time span nor that it merged with another large galaxy, either.

As a final observation, galaxies with active supermassive central black holes typically are also seen spewing enormous jets of matter and energy. These jets are not always discernable in visible light but can be spotted in other wavelengths such as infrared and x-ray and stretch distances that are longer than the galaxy is wide.

I was able to take a long exposure image of a galaxy with a jet that, uniquely, IS visible in white light. Here's a link so you can see what I mean:

http://antwrp.gsfc.nasa.gov/apod/image/ ... bany_f.jpg

I hope this makes sense.


Jay