APOD: Grand Spiral Galaxy NGC 1232 (2012 Jan 07)

[APOD Robot]

Grand Spiral Galaxy NGC 1232

Explanation: Galaxies are fascinating not only for what is visible, but for what is invisible. Grand spiral galaxy NGC 1232, captured in detail by one of the new Very Large Telescopes, is a good example. The visible is dominated by millions of bright stars and dark dust, caught up in a gravitational swirl of spiral arms revolving about the center. Open clusters containing bright blue stars can be seen sprinkled along these spiral arms, while dark lanes of dense interstellar dust can be seen sprinkled between them. Less visible, but detectable, are billions of dim normal stars and vast tracts of interstellar gas, together wielding such high mass that they dominate the dynamics of the inner galaxy. Invisible are even greater amounts of matter in a form we don't yet know - pervasive dark matter needed to explain the motions of the visible in the outer galaxy.

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[Beyond]

Yes, it does look rather Grand, doesn't it. I think I'll just sit and watch it spin for a while.

[Ann]

Yes, it does look rather Grand, doesn't it. I think I'll just sit and watch it spin for a while.

Beyond, I always enjoy your sense of humour. Your remark reminds me of a cartoon I once saw of Fritz Zwicky, a brilliant but probably Slightly Mad Professor, who was very interested in supernovae. In the cartoon, Zwicky, almost trembling with energy and anticipation, stood staring at a patch of sky through his telescope. His assistant lay down on a makeshift bed, saying good night to the Professor with the following words: "Wake me up if anything explodes up there, Professor!"

Ann

[Ann]

On a more serious note, NGC 1232 is an interesting galaxy. What I find remarkable about it is its sheer number of thin arms. On the left side of the galaxy, I think you can count to either six or seven thin arms.

NGC 1232 is a spiral galaxy of Hubble class Sc, meaning that the galaxy has a small bulge and long arms that flare out widely from the center of the galaxy. It belongs to luminosity class 1, which means that it is large and bright. According to Principal Galaxy Catalog, NGC 1232 shines with the light of 50 billion stars like the Sun and is about 2.2 times as bright as the Milky Way.

I find it remarkable that such a large and bright mass conglomerate can be so intricately structured. It is much easier to understand, for me at least, that jumbled and chaotic structures like elliptical galaxies can put on mass and grow larger and larger.

NGC 1232 has a small satellite galaxy, NGC 1232A. For a long time it was a mystery that NGC 1232A seemed to have a redshift that would put it more than twice as far away as NGC 1232. According to Wikipedia, however, astronomers now put NGC 1232 and its satellite at similar distances:

In 1988, NGC 1232A was estimated to be 68 million light-years away[4] while NGC 1232 was estimated to be 65 million light-years away.

My software says that when the distances to these two galaxies are estimated from neutral hydrogen, the Virgo infall and the 3K background, as well as from the Local Group and the Galactic Standard of Rest, then the two distances are similar. But when the distances are estimated from optical observations, the radial velocity of NGC 1232A is 4062.500 +/- 2452.867 km/s, but for NGC 1232 the radial velocity is 1704.577 +/- 62.875 km/s.

I guess the discrepancy could be explained by the huge margin of error for NGC 1232A.

Ann

[starchaser]

Amazing, the jewel box that is Cosmos never ceases to amaze me!

Thanks Ann, I was just going to ask about the object at 8 o'clock, but your post was informative as usual.

[orin stepanek]

Beautiful galaxy! I think Grand can be used to describe a lot of galaxies!

[eltodesukane]

Yes, it does look rather Grand, doesn't it. I think I'll just sit and watch it spin for a while.

Beyond, I always enjoy your sense of humour. Your remark reminds me of a cartoon I once saw of Fritz Zwicky, a brilliant but probably Slightly Mad Professor, who was very interested in supernovae. In the cartoon, Zwicky, almost trembling with energy and anticipation, stood staring at a patch of sky through his telescope. His assistant lay down on a makeshift bed, saying good night to the Professor with the following words: "Wake me up if anything explodes up there, Professor!"

Ann

This (unrelated) comic made me laugh a few days ago
[img2]http://i42.tinypic.com/vqmjj4.png[img2]
http://www.ottawasun.com/2011/12/30/january-2-2012

[moonstruck]

What are the small orange dots scattered all over the page? I suppose galaxies far, far away?

[Ann]

What are the small orange dots scattered all over the page? I suppose galaxies far, far away?

Good question. Many of them look too "compact and concentrated" to me to be galaxies. I think that several of them are stars.

Why are they so orange? I think it has to do with the filters used to produce this image. If you check out this page, you can see that the filters used were ultraviolet, centered at 360 nm, blue, centered at 420 nm, and red, centered at 600 nm.

This means that the picture was produced using two short-wavelength filters and one orange-red one. (Please note that even the blue filter at 420 nm is really centered on indigo light rather than on blue light.)

Most stars in our galaxy are of spectral class M. They emit much of their light in the orange-red part of the spectrum, but they emit very little (or extremely little) blue light and even less ultraviolet light. These stars will be clearly detected by the red filter that was used to produce this image, but the blue and ultraviolet filters will only marginally detect them. The result should be a number of orange-looking stars.

Ann

[moonstruck]

Thanks for the info and the link Ann. You da woMAN.

[Ann]

Thanks for the info and the link Ann. You da woMAN.

Thanks!

Ann

[Wolf Kotenberg]

Did dark matter exist before the Big Bang ?

[Chris Peterson]

Did dark matter exist before the Big Bang ?

Nothing existed before the Big Bang. There wasn't even a "before" the Big Bang, since time didn't start until then, either.

[saturn2]

The Spira lGalaxy N G C 1232, has visible matter ( millions of bright stars ) and dark matter what is in the interstellar space, but into of the galaxy.
Visible matter vs. dark matter.
The dark matter is important in the Universe, but is necesary more study. It´s true?

[saturn2]

I think that the dark matter existed before the Big Bang.
I think that the barionic dark matter was the base for the Big Bang.
Barionic dark matter ---Big Bang ----barionic visible matter-----galaxies
( Barionic dark matter and not barionic dark matter are the total dark matter in the Universe. )

[Chris Peterson]

I think that the dark matter existed before the Big Bang.

Dark matter is... matter. A form of energy. Every form of Big Bang theory agrees on one point: at the very beginning, the temperature was too high to allow for anything other than energy to exist. There was no matter- dark or otherwise. Matter could only form when the temperature dropped enough to allow the necessary phase changes to occur, the different forces to separate, and the property of mass to develop. These things happened a short- but finite- time after the Big Bang.

It is basically meaningless to talk about "before" the Big Bang, and if you accept any Big Bang cosmology at all, it makes no sense to believe that dark matter preceded, or was even coincident with, that event.

[Sergio]

Thanks Ann for yor nice description

A perfect face on spiral galaxy. This object is quite a challenge for astro imagers. Despite its relative high magnitude it has with very low brightness surface.

Best Regards
Sergio

[kopernik2]

Just came across the NGC 1232s. This fits nicely with what I call ‘mitosis’ of a galactic nucleus, and will use it as an example. In mitosis (there is also mieosis) the nucleus (which I believe is composed of multiple black holes) ruptures due to dynamic forces and one or more parts (still composed of multiple BHs) are flung away. These may stay near the center of the galaxy or my migrate far beyond. Characteristics are the two galaxies are – rotating in the same direction (original’s rotation) and most often both have a bar shaped nucleus and spiral arms. Neither seem to seriously interfer with the other gravitationally. The configuration of the original nucleus was of a chain-like rotating string of black holes.
If you want to check my website, look up in Part One Mitosis.

[Cavemanview]

The mention of dark matter in this post makes me wonder about a couple of things. These are fundemental questions and I apologize for my naivete but I am not a trained professional in these matters, only a curious fellow staring at the stars.

Why is it that visible matter coalesces into stars and dark matter does not. Maybe it does, but how would we know? They apparently both have mass and dark matter apparently has effect on visable matter. What would the characteristics of a 'dark star' be?

The other thing that makes me wonder is why are most galaxies flat spinning collections of stars and dust? It seems to me that a big bang would produce a universe more three demensioal and sysmetrical (spherically). Why the flatness? I suspect this is explainable but is beyond my current knowledge to understand.

[Chris Peterson]

Why is it that visible matter coalesces into stars and dark matter does not. Maybe it does, but how would we know? They apparently both have mass and dark matter apparently has effect on visable matter. What would the characteristics of a 'dark star' be?

Ordinary matter can condense to high densities because it interacts with itself through a variety of forces other than gravity. Otherwise, each particle would simply orbit the common center of mass of its region (which is just what dark matter does, and explains why it exists in a spherical halo around galaxies). Because of other interactions, you get fluid dynamic effects, such as frictional heating, that rob particles of energy and converts gravitational potential energy into heat. The result is compact, hot objects- stars, for example.

The other thing that makes me wonder is why are most galaxies flat spinning collections of stars and dust? It seems to me that a big bang would produce a universe more three demensioal and sysmetrical (spherically). Why the flatness? I suspect this is explainable but is beyond my current knowledge to understand.

This is also a product of the various interactions that exist between particles of ordinary matter. While a diffuse cloud contains particles with nearly random angular momentum values, the cloud as a whole will always have some net angular momentum. As particles collide and interact via electromagnetic forces, angular momentum is transferred. The end result is that the majority of material ends up with similar angular momentum (or more accurately, they have angular momentum vectors pointing the same way; they will have a range of magnitudes), which is only possible if everything is orbiting on a plane. This is also the reason that stellar systems form in a plane, and why accretion discs are actually discs.