Starship Asterisk*

NGC 922: Collisional Ring Galaxy

Explanation: Why does this galaxy have so many big black holes? No one is sure. What is sure is that NGC 922 is a ring galaxy created by the collision of a large and small galaxy about 300 million years ago. Like a rock thrown into a pond, the ancient collision sent ripples of high density gas out from the impact point near the center that partly condensed into stars. Pictured above is NGC 922 with its beautifully complex ring along the left side, as imaged recently by the Hubble Space Telescope. Observations of NGC 922 with the Chandra X-ray Observatory, however, show several glowing X-ray knots that are likely large black holes. The high number of massive black holes was somewhat surprising as the gas composition in NGC 922 -- rich in heavy elements -- should have discouraged almost anything so massive from forming. Research is sure to continue. NGC 922 spans about 75,000 light years, lies about 150 million light years away, and can be seen with a small telescope toward the constellation of the furnace (Fornax).

<< Previous APOD

This Day in APOD

Next APOD >>

[/b]

Yes! Today's APOD really is NGC 922!

And what a galaxy it is. It is relatively large, probably not larger but at least brighter than the Milky Way, and tremendously star-forming and therefore very blue and pink. All these stellar fireworks were set off by a near-collision with another galaxy, of course. So why are there so many black holes in NGC 922? I can't answer that, of course, but in my opinion there aren't many galaxies like NGC 922 nearby - so large, so blue, so starforming. A galaxy like this one must contain very high numbers of O-stars, the most massive and luminous stars, and also a number of ultra-massive and ultra-luminous O-stars.

Sounds like a perfect recipe for cooking up black holes to me!

Ann

I have seen a 3/4 Moon, but not a 3/4 Galaxy....well, now I have...

:---[===] *

This is one of my favourite southern peculiar galaxies, look at all the star formation triggered by the initial interaction and subsequent merger!!! I don't like that "violent" language is used to describe galaxy collisions, to me its like galactic lovers in an embrace!

Although the HST field of view isn't large enough to show them, this galaxy also has very nice tidal tails and streams, which I guess would be visible in a large field amateur image.

Surprising! Very interesting APOD! I enjoyed the Hubble video!

.
[list]King Lear Act 4, Scene 6[/list]
EDGAR: O, matter and impertinency mix'd! Reason in madness!
MIX, v.t. [L. misceo, mixtum; Heb. to mix.] To unite or blend promiscuously two or more ingredients
into a mass or compound; applied both to solids and liquids; as, to mix flour and salt; to mix wines.

starsurfer wrote:This is one of my favourite southern peculiar galaxies, look at all the star formation triggered by the initial interaction and subsequent merger!!! I don't like that "violent" language is used to describe galaxy collisions, to me its like galactic lovers in an embrace!

I agree starsurfer, collision is too violent a term for galactic mergers. And since the birth of many new stars is often the result, these mergers are rather procreative in nature, are they not?

As to the question raised in the Explanation, “Why so many black holes?” aren’t most large galaxies suspected of having numerous black holes in addition to the SMBHs at their centers, such as proposed intermediate BHs at the core’s of globular clusters? If that were the case couldn’t the merger be causing several otherwise undetectable BHs to light up in X-rays due to in-falling material (gas, dust, and rarely an unfortunate star) from the other galaxy?

Bruce

BDanielMayfield wrote:

starsurfer wrote:This is one of my favourite southern peculiar galaxies, look at all the star formation triggered by the initial interaction and subsequent merger!!! I don't like that "violent" language is used to describe galaxy collisions, to me its like galactic lovers in an embrace!

I agree starsurfer, collision is too violent a term for galactic mergers. And since the birth of many new stars is often the result, these mergers are rather procreative in nature, are they not?

As to the question raised in the Explanation, “Why so many black holes?” aren’t most large galaxies suspected of having numerous black holes in addition to the SMBHs at their centers, such as proposed intermediate BHs at the core’s of globular clusters? If that were the case couldn’t the merger be causing several otherwise undetectable BHs to light up in X-rays due to in-falling material (gas, dust, and rarely an unfortunate star) from the other galaxy?

Bruce

I'm not too interested in black holes myself and don't know that much about them, but my understanding is that NGC 922 is unusually rich in so-called ultraluminous X-ray sources, which are believed to be stellar mass black holes feeding on a hapless companion. It could be that many of these black holes are "young", and they may be a product of the extremely vigorous star formation in this galaxy. Because of their youth, they are also quite likely to have a bloated stellar companion to feed off of.

For comparison, I wouldn't think that a large galaxy like Andromeda has as many ultraluminous X-ray sources as NGC 922. Presumably many of Andromeda's black holes are older, and they have already "eaten" all the nearby morsels. Therefore, many of these black holes are "quiet".

Ann

I see a lot of dust in the upper part. It is superbig. After the collision the dust is not much dispatched into a ring shape like the stars, but it seem still in connection with the bulge.

APOD Robot wrote: The high number of massive black holes was somewhat surprising as the gas composition in NGC 922 -- rich in heavy elements -- should have discouraged almost anything so massive from forming. Research is sure to continue.

If you ever want to get rid of something… throw it in a black hole… and if you get close enough… no one will see you do it.

So tell me. Do if galaxies like this with lots of black holes in them just suck in lots of matter (if it happens to be around) or do they suck in space too?

Ron-Astro Pharmacist wrote:So tell me. Do if galaxies like this with lots of black holes in them just suck in lots of matter (if it happens to be around) or do they suck in space too? :roll:

Black holes suck in matter. And not very much of that.

Ron-Astro Pharmacist wrote:
So tell me. Do if galaxies like this with lots of black holes in them just suck in lots of matter (if it happens to be around) or do they suck in space too?

they suck in any matter that happens to reside in that space.

neufer wrote:Black holes suck in space.

I think that interpretation is a stretch. And any discussion of what happens inside a black hole is highly speculative.

Chris Kruskal wrote:

neufer wrote:
Black holes suck in space.

I think that interpretation is a stretch.

And any discussion of what happens inside a black hole is highly speculative.

• And I'm more than a little Szekeres to discuss it, myself.

http://en.wikipedia.org/wiki/Kruskal%E2%80%93Szekeres_coordinates wrote:

[b][color=#0000FF]Kruskal-Szekeres diagram. Each frame of the animation shows a blue hyperbola as the surface where the Schwarzschild radial coordinate is constant (and with a smaller value in each successive frame, until it ends at the singularities).[/color][/b]

---

<<In general relativity Kruskal–Szekeres coordinates, named for Martin Kruskal and George Szekeres, are a coordinate system for the Schwarzschild geometry for a black hole. These coordinates have the advantage that they cover the entire spacetime manifold of the maximally extended Schwarzschild solution and are well-behaved everywhere outside the physical singularity.

Kruskal–Szekeres coordinates are defined, from the Schwarzschild coordinates, by replacing t and r by a new time coordinate V and a new spatial coordinate U:




for the exterior region r > 2GM, and:




for the interior region 0 <r <2GM.

Art (generally well-behaved EVERywhere outside the physical singularity) Neuendorffer

NGC 922 has " high number of black holes"
Very intersting
More Interesting
In the link " somewhat surprising" there is a image of a dog ????
I don´t understand

the collision of two black holes spewed fragments of black holes..

saturno2 wrote:NGC 922 has " high number of black holes"
Very intersting
More Interesting
In the link " somewhat surprising" there is a image of a dog ????
I don´t understand

The image of the dog is there just for fun, to lighten the mood a bit. I think it's a sweet dog, but it doesn't mean anything particular here.

It is in fact quite common that one link of each APOD leads to a picture of a dog or a cat. It doesn't happen with every APOD, not at all, but it is in fact quite common.

Ann

Ann
Thanks for your explanation

I think what I was curious about was," What effect would the loss of space around a black hole have on our galaxy?" And what effect would black holes, far from here, have on space in general if they did indeed get "sucked" or get pulled into the black holes - on large areas of, whatever it is that we call "space". Another question (and unfortunately I have plenty)," Where does the space and the matter pulled into the black hole go?" Into another universe?? Also, would the loss of space affect relativity? Sorry we amateurs know so little but are curious

Ron-Astro Pharmacist wrote:I think what I was curious about was," What effect would the loss of space around a black hole have on our galaxy?" And what effect would black holes, far from here, have on space in general if they did indeed get "sucked" or get pulled into the black holes - on large areas of, whatever it is that we call "space". Another question (and unfortunately I have plenty)," Where does the space and the matter pulled into the black hole go?" Into another universe?? Also, would the loss of space affect relativity? Sorry we amateurs know so little but are curious :o

Space isn't disappearing into black holes. Space is distorted around black holes, in the same way it is around all massive objects. If there is, in fact, a singularity at the center of black holes, than you might think of this as a point where space has been removed from the Universe... but it's an infinitesimally small amount of space!

Black holes are not affecting the Universe in any unusual way.

Chris Peterson wrote:

Ron-Astro Pharmacist wrote:I think what I was curious about was," What effect would the loss of space around a black hole have on our galaxy?" And what effect would black holes, far from here, have on space in general if they did indeed get "sucked" or get pulled into the black holes - on large areas of, whatever it is that we call "space". Another question (and unfortunately I have plenty)," Where does the space and the matter pulled into the black hole go?" Into another universe?? Also, would the loss of space affect relativity? Sorry we amateurs know so little but are curious

Space isn't disappearing into black holes.

I disagree.

Space IS disappearing into black holes;
but then space is also falling into our own Sun.

The space around the earth falls into the Sun every 64 days (~ a year/sqrt(32)).

If the Earth were standing still (vis a vis the Sun) the Earth would join space in that plunge.

However, the Earth avoids that fate by leaving its space at ~30km/s.

We used to worry that the Big Bang would lose its punch
and that all of space would disappear back into a Big Crunch.

But thanks to Dark Energy Space is constantly being renewed at a rapid pace.

neufer wrote: Space IS disappearing into black holes;

I disagree. The spacetime of a Schwarzschild black hole, as described by the Kruskal-Szekeres coordinates, is static. What does change with time is the position of free falling particles and photons, which move on geodesics. The waterfall analogy mentioned in the movie is, IMHO, to be interpreted such that the curvature of spacetime can become so strong that no matter how strong you "paddle" you cannot escape the black hole, once past the event horizon. Furthermore, how do you measure the "flow of space" (and not the flow of matter)?

neufer wrote: The space around the earth falls into the Sun every 64 days (~ a year/sqrt(32)).

If the Earth were standing still (vis a vis the Sun) the Earth would join space in that plunge.

However, the Earth avoids that fate by leaving its space at ~30km/s.

Interesting. Where did you get that?

Markus Schwarz wrote:Interesting. Where did you get that?

I think he's just using the time it takes to fall 1 AU under the gravitational acceleration of the Sun.

As you say, that is how bodies with mass behave under gravitation, which is modeled as a distortion of spacetime. It doesn't describe the motion of spacetime itself. Indeed, as I understand GR, the motion of spacetime isn't even a defined concept. I don't know- physically or mathematically- what it means for "space to disappear" into a black hole or any other mass. Under GR, space is a coordinate system, not a physical thing.