Gravitational Lens ??

[ElChristou]

Hello,

Do a gravitational lens could look like this?

[t00fri]

Hello,

Do a gravitational lens could look like this?

ElChristou,

you would not see a gravitational lens as such in space!
So the answer to your question is NO.

The gravitational field due to a huge foreground mass (galaxy cluster etc) deforms the geometry of space!
Since light rays from background objects (far away galaxy,...) always follow the "geodesics" of space geometry -- like rivers flow in the mountains-- the light rays are bent and derouted like if they'd pass through a lens. Hence we see an image of the light emitting object located much further away than our foreground mass, that is distorted in a characteristic way.

That's the phenomenon of gravitational lensing.

Here is a nice illustration


from

http://en.wikipedia.org/wiki/Gravitational_lens

Bye Fridger

[ElChristou]

Ok, so this kind of optic distortion only takes place in deep field, around galaxy clusters for example... Inside a galaxy, do a black hole can create such lens (when observed from a safety distance of course)?

[t00fri]

Ok, so this kind of optic distortion only takes place in deep field, around galaxy clusters for example... Inside a galaxy, do a black hole can create such lens (when observed from a safety distance of course)?

certainly

Bye Fridger

[ElChristou]

certainly

Last question, at the opposite of a "galactic" lens, the distorch effect around a black hole will ge greater when approching, right?

[ElChristou]

I've have my response... I've came over this page (http://casa.colorado.edu/~ajsh/schw.shtml) and the description of the falling into a BH is quite easy to understand... I'm wondering if all this is really accurate...

[eburacum45]

How did you make this image, ElChristou? I have been looking for a way to make the gravitational lensing around a wormhole in Celestia for a while now.
According to this link wormholes (if they exist) would have similar lensing to a black hole;
http://arxiv.org/abs/gr-qc/0505054

so this sort of lensing would be detectable in a wormhole image.

[ElChristou]

Unfortunatly it's not a lens within Celestia, just a Photoshop distorch filter...
Making such lens is a question of coding, and unfortunatly it's not my cup of tea...

Bye

[eburacum45]

Oh well; I can get that effect using the Gimp, with a little tweaking. Thank you.

[maxim]

Making such lens is a question of coding, and unfortunatly it's not my cup of tea...

It's not just a question of coding. There's a lot of prerequisite work on this.

First, according to the required masses, you'd need the concept of galaxy clusters as seperate objects beeing defineable and renderable inside Celestia. That's definitely more than Fridgers galaxy catalog can support currently. Actually 10000+ galaxies may be not even the sum of what our nearest neighbour - the Virgo Cluster - contains. So you need a seperate catalog on clusters and the ability to render it.

Second you need mass values for the clusters in order to compute the lens distortion effect - there may be no catalogs on clusters that contain such an information.

Third you'd need some real distant galaxies that can be watched throught the grav-lens.

The visual lens effect itself may be quite simple to code. It's not a very complex formula.

I admit that it could look /very/ cool to watch such lens effects in real time throught a virtual deep field mode inside Celestia. But there would be a bit of work in the forehand.

maxim

[eburacum45]

This is one of the Orion's Arm wormholes with a bit of lensing applied; the purplish structure is the negative energy framework holding the hole open. I had to add the spaceship to the image after adding the lens effect because that is in front of the hole, so is not affected by the lensing effect.

[img=http://img66.echo.cx/img66/1143/ship7ez.th.png]

[ElChristou]

Maxim,

You are perfectly right... Now what about a black hole? Is there a way to create some kind of bilboard with soft edges, on with the distorch filter can be applied? I'm curious to see in real time this kind of stuff... I know it won't be very "scientific" but this can give some idea for *perhaps* some more serious works...

[t00fri]

...
First, according to the required masses, you'd need the concept of galaxy clusters as seperate objects beeing defineable and renderable inside Celestia. That's definitely more than Fridgers galaxy catalog can support currently. Actually 10000+ galaxies may be not even the sum of what our nearest neighbour - the Virgo Cluster - contains. So you need a seperate catalog on clusters and the ability to render it.
....

Wait a second

Since 2 weeks I am up at 25000+, but I agree when looking at the SDSS survey things are getting interesting at the level of 100000+ ...

Still, 25000+ galaxies corresponds to the biggest Pro catalog before SDSS. The latter targets at 15 Terabyte (!) of raw data ...Anybody ready for a new HD?

In fact, I generated a few very neat views of clusters of galaxies with the new data! Right now I am working on Toti's new culling code (galaxy octree!) to hopefully get back to impressive fps rates.

Bye Fridger

[maxim]

Since 2 weeks I am up at 25000+, but I agree when looking at the SDSS survey things are getting interesting at the level of 100000+ ...

Well, do you think this amount will be enough to let us consider about grav lens effects?

Still, 25000+ galaxies corresponds to the biggest Pro catalog before SDSS. The latter targets at 15 Terabyte (!) of raw data ...Anybody ready for a new HD? Laughing

The big stars database (2000000+) needs about 50 MB on my harddisc. I think there is room for improvement on galaxy data storage.

You are perfectly right... Now what about a black hole? Is there a way to create some kind of bilboard with soft edges, on with the distorch filter can be applied? I'm curious to see in real time this kind of stuff... I know it won't be very "scientific" but this can give some idea for *perhaps* some more serious works...

I think it would the same as with stars. Remember that stars also have a grav lens effect (as one can see during solar eclipses). Black holes are far nearer to stars, considering mass values, as to galaxy clusters. So there will be a thin halo with grav lens influence around a black hole as it is around a star. Probably a shader would be the most obvious way to render such an effect, and make it available for every star in Celestia - similar to atmospheres.

If a shader could do it, you should ask Chris about this.

maxim

[ElChristou]

...If a shader could do it, you should ask Chris about this...

With all the work in progress + bug fixing from long date awaiting, I won't bother him with this... later perhaps...

Bye

[Gerbil94]

Do a gravitational lens could look like this?

That lens appears to be stuck in a galaxy - is this to be a microlens (lensing by a star?). The thing about microlensing is that the image splitting (or the radius of significant distortion) is very small, only a few micro-arcseconds. I doubt that would span much of Celestia's field of view. You can't improve matters by moving closer to the lens, either, because the splitting angle depends on the observer's position and if you move closer you just won't see distortion/multiple images of the background source.

If you replace the star with a black hole, then the same problems remain. However, if you move close enough to the black hole (approach the event horizon - few km distance) then I guess you're in a strong field situation (gravitational lensing calculations in astronomy assume weak fields most of the time). I assume the distortions would get pretty wild, but that's not microlensing anymore and I don't know that you could do it in real time.

If this is meant to be galaxy- or cluster-scale lensing, then, as t00fri pointed out, there is no obvious lens mass there. No examples of lensing caused by dark galaxies ("dark lenses") are known at present (we would expect to have found a few of them if they are there).

Finally, it's quite difficult for me to tell on this monitor (does the image seem very, very dark to anyone else?), but the lens distortion effect looks wrong. For a general idea of how a lens-distorted image should look, try the logo at the top of this page. Note how the distortion produces an inverted image of the background inside a certain radius (the Einstein radius in real lenses - depends on the lens mass). I think there are several photoshop filters around to do this sort of thing - perhaps this if you haven't found it already.

[ElChristou]

Many tx for this complement of information, since a few days I'm looking for more on the net an I begun to have a better idea of the lens effect. The picture of my post was a quick photoshop distorch filter, really nothing serious. About Photoshop filter, I cannot test the one you point me out because it is not available on osX, but I will test the one from Pete Kernan...

Tx again,
Bye

[birthplace]

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[t00fri]

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[ElChristou]

You see ElChristou ,

your exciting questions about gravitational lenses seem to also attract those doubious Russian characters like flies...

Ouch... I know this question was sensitive... but at this point!!