Celestia Forums

I just uploaded to the Motherlode a new addon for Celestia : black holes in the 47 Tucanae globular cluster. I hope it will be available in the next few days, at the web page

http://www.celestiamotherlode.net/catal ... hp#systems

It's fun to watch averything moving around the black holes, and the flares around the star companion-meal.

Here are some preview pictures from the addon :









Any opinion and critics are welcome here.

Looks nice, Cham.

I'll have to go download it and check it out, but from the screenshots I like it already.

Here are four other views of the addon :

This is a view of the second black hole (its meal is far away) :


This is a view of the Ogre, with its meal in the background :


This is a view from the inside of a jet. With the animation, this is totally psychedelic :


Another shot at close range (yikes ! The event horizon isn't far and we're gonna enter the ergosphere !) :

Ok, here some critics to the appearance (they may sound much more negative than they are):

- The whole thing looks too sharp and clean. Much more like a lollipop than like a aggregation disk.
- Are you shure about the colors? Shouldn't they go from IR to UV instead of vice versa.
- What about turbulences? Is this really supposed to be a clean flow, instead of some heavy turbulence areas?
- Shouldn't the jets be much more faint and blurry and in the near UV? Can jets be seen at all, if not looking directly onto them?

maxim

Good questions.

Sharp and clean, I can't tell. But I'm sure it will emit a HUGE amount of light. There are lots of red hot plasma moving at relativistic speed around the black hole. And because it's moving VERY fast, I don't think we could see any graininess, lumps or turbulences in the close accretion disk (the lollipop). The lollipop is actually a rough representation of the "ergosphere" around the black hole. Matter inside the ergosphere (outside the event horizon) is FORCED by the black hole to rotate fast with the black hole. It's a general relativistic effect and a feature of the "Kerr black holes" (steady state rotating black hole). The size of the first accretion disk (which is looking like a lollipop) is largely exagerated for aesthetical reason only.

I'm not sure about the colors, but one thing is sure : relativistic Doppler effect and relativistic GRAVITATIONAL REDSHIFT. From a distance, everything close to the black hole should be redish, especially the falling objects.

Turbulence should be visible only in the accretion disks away from the black hole. Matter moving close to it will moves at highly relativistic speed, and they'll form a pretty sharped, almost clean, pattern. The pattern itself may be slowly moving for an outside observer, but the particles themselves will not be visible (of course) and traveling at almost the speed of light.

The jets are highly relativistic particles moving away from the black hole, and trapped in the intense magnetic field created by the black hole itself and the plasma rotating around. So it should produce a lot of blue light, radio waves, x rays, gamma (all the electromagnetic spectre, I guess). They should form very precise, sharp jets. But I'm not sure on the jets shape. I'd love to be able to make things blurry in Celestia, but currently, this isn't possible

I had to take a decision about the colors:

The colors are very observer dependant. If the observer is moving, there is some Doppler effect, which Celestia isn't able to render. If the observer is close to the black hole, everything around him (matter in the immediate vicinity of the black hole) should looks extremelly blueish, because of the very high temperature of the plasma. But if an observer is far away from the black hole, the matter close to the black hole should appears reddish, because of two effects : 1-Doppler effect of moving matter falling into the black hole, and 2-gravitational redshift. For a black hole, the second effect is VERY strong.

Because most people will look at the black hole from a distance, it should be in some red tonality, not blue. That's why I selected reddish colors instead of blue ones.

However, maybe I should have made the second accretion disk blueish at the external borders. That's the disk which is precessing, because of the Lense-Thirring effect (there are some turbulences in this disk). The last (third) accretion disk should be brown-red and darker, because temperature is lower there, and there is a weaker gravitational redshift.

... Just love the screenshots!

-rthorvald

Maybe a small warning is necessary here, about the features to be enabled in Celestia. Everything is moving and rotating (even the flares on a star, like the real thing). There is no bumpmap, no specular reflection, and no textures are bigger than 2k. So it should run fine on most hardware. However, I use heavily some simple 3ds models (mostly planes and cones), and the commands "Barycenter" and "PrecessionRate".

*** So, because of the "Barycenter" command, I guess you'll need at
*** least Celestia 1.4.0. If you are using Celestia 1.3.2, you will have
*** to edit the stc and ssc files to remove all references to the
*** Barycenter, and put the Black holes in orbit around their companion star.

I hope it wont be too long before the guys at the Motherlode will make the addon available.

Cham wrote:I hope it wont be too long before the guys at the Motherlode will make the addon available.

It's now available on the Motherlode, here.
But - as I wrote before - it'd be nicer to wait with any announcements until the file is actually available for download.

Harald

Harry wrote:But - as I wrote before - it'd be nicer to wait with any announcements until the file is actually available for download.

Harald

You are right. I apologise for my impatient behavior.

Sorry.

I just realised that, because of the Barycenter command I'm using in this addon, only people with Celestia 1.4.0 or later may use the addon without modifications. If you're on Celestia 1.3.2, you will have to edit the stc and ssc files to put the Black holes in orbit around their companion star. If you edit the files, make sure to edit all the accretion disks and the jets too.

Well, I hadn't the chance to watch a aggregation disk from closeup yet, but that's what I would expect about to happen:

In the outer rims, where the aggregated matter has enough room, there is a dim glow of yellow or red from the moderately heated particles, and some laminal non-turbulent streams in direction of the black hole. Further inside the matter gets hotter, because there is now much more interaction between particles, and there will also be some turbulences because of that. The more we get inside, the more, and more intense energy is emitted by the interacting matter, but this tends to be more and more in the x-ray part of the spectrum. So the radiation gets more and more bluish until it becomes invisible to the eye inside the inner disk around the black hole. The outer laminal streams become turbulent, until the speed and interaction is so high that there can't be seen anything more than a uniform glow - no more streamlike patterns in the inner agreggation disk.

The doppler effect may only cause, that if seen from the side, the matter left from the hole - rotating away from the viewer - will look more red, while the matter on the right side of the hole will look more blue. If looking onto the hole from straight above, no doppler effect could be seen at all.

The jets will be 'sharp' in a astronomic meaning - that means +- 1 million kilometers are still quite sharp. If they are very sharp, they can't be seen from the side. If they can be seen from the side they can't be very sharp. The jets will also be turbulent, because they are slowing down along their axis. Their energy output will degrade along their axis, so the color will be from invisible (that's properly adressed because the jets APPARENTLY start from some distance to black hole) to blue and yellow in the end. Thought it looks nice, I don't think one could look throught them and watch the black hole. For the modelling I would propose to put a second semi-transparent cone around the first one to deal with the blurryness.

BTW: The aggregation disk and the jets emits a HUGE amount of ENERGY. That does not neccessarily mean that this corresponds to the output in the VISIBLE part of the spectrum.

maxim

How on Earth do I get hold of 1.4.0? I haven't ben able to find it for downloading anywhere. Is it some sort of limited release?

Maxim,

don't forget the gravitational redshift, which is dominent in the close vicinity of any black hole. Even x rays (at the emission location) could becomes of red wavelenght, or even radio waves, to an outside observer.

I agree that the jets should be, at least, a bit blurry. But I can't do this in Celestia. Yesterday night, I added another cone which adds a weak "bit" of bluriness. But that's the best we could do right now.

About the jets color, well, I'm not sure. They are made of highly relativistic particles. Turbulence ? That's not obvious, but if you slow down time by a 10 factor (or more), you'll see that I made a lot of turbulence in them. I expect a red jet close to the black hole, because of the gravitational redshift. At some distance away, it should become blue, and after that it should be invisible.

Anyway, wathever the limited realism of my black hole, I think it is far more satisfying than the other black holes made for Celestia.

Cham, i just got this up and running. Your addon is incredibly cool!
... And more than a little psychedelic

-rthorvald

Sorry,Cham.
I can??t see the second black hole.I can see the stars riping apart,the flares,but not the black hole.I can??t write Ogre??s navel correctly and when I go to "Banquet",there isn??t any black hole nearby or orbiting it.The first black hole is clearly visible,though.
I am using Celestia 1.4.0 pre6,a Geforce FX 5700 and NVIDIA driver 67.22.

danielj wrote:Sorry,Cham.
I can??t see the second black hole.I can see the stars riping apart,the flares,but not the black hole.I can??t write Ogre??s navel correctly and when I go to "Banquet",there isn??t any black hole nearby or orbiting it.The first black hole is clearly visible,though.
I am using Celestia 1.4.0 pre6,a Geforce FX 5700 and NVIDIA driver 67.22.

The first black hole, can you see it in orbit around the star named "EGO", with all its accretion disks ? If so, you should see the Ogre too.

In Celestia, type this : Ogre's navel/Ogre, and type "return". It should be selected. The Ogre is a much smaller object than "Banquet", but they are both in orbit about their barycenter which I called "Ogre's navel".

For some reason,now I can??t see the Black EGO black hole,but I can see the Ogre??s navel.When I type Black EGO or HIP 805006,the star appears,but nothing is orbiting it.Is it possible that one addon interfere witn the another?
I also have a criticism.You represented the center of the black hole more or less like a black dwarf.But the center of the black is a "empty" place and don??t have anything to do with a black dwarf.Anyway I like very much the way you represented the gases spiralling away,and the protuberances(proeminences) in "The Banquet".I also like that you can zoom in the black hole by the gas jets.
But I don??t understand what do you mean that if I increase the speed to 1E7,you wold see the bulge drifting away from the black hole.I don??t think I have seen such a thing.Can you explain better?

The black hole around EGO is very small, compared to its star companion, and at some distance of it. You have to select it by entering "Black Ego/Black Hole". No, there isn't any interference between the two black holes. If the Ogre is visible, then the other black hole is certainly working too.

The "Black dwarf" aspect is a feature. There is a not known enough thing about black holes : the black hole "skin". Very near the "event horizon", matter appears to "slow down" relative to an outside observer. Matter appears to build a kind of thin, superconducting skin. This is a fascinating subject. So the "spiral" on the event horizon is really representing something about the black hole. Real black hole is NOT just a black or invisible sphere.

In my addon, I've found a way to make the bulges aligned for a pretty long time. In this case, you must accelerate time by a 1E10 factor to see the bulges drifting away.

Now I can see,but I thought that the Black EGO black hole should be orbiting the star "EGO",but it isn??t.
I don??t understand very much what the bulges are.Is it something related to the jets?Or is it the material spiraling from the star into the black hole?