Celestia Forums

Ok so I'm sure you guys have heard of the Primeval planet, the 12.7 billion year old Juggernaut orbiting in a binary system where the primary is the star PSR B1620-26 a 1.35 MSol Pulsar, and the secondary is a .4 MSol white dwarf.

The planet orbits with a semimajor axis of 23 AU or so, and has about 2.5 Jupiter masses. I bring this system up for a couple of reasons. First its bizzare nature, and second, the possibility of modeling this system in future releases of Celestia.

Although my contributions to Celestia are now largely obsolete I have not lost interest in the medium. Moving away from school and being seperated from my computer for a very long time not withstanding, I'll be contributing again soon enough (I eagerly anticipate the release of v 1.3.1). Anyway enough ranting, here is the deal.

Has the "avoidance problem" I brought up in past posts, been fixed in V1.3.1 or will it be fixed in a future release. For those of you who do not know, one can only place a star so close to another star in Celestia before the two merge. Chris explained that this has something to do with the limits of detectability and observability from Earth. Apparently the greater distance a star is from Sol the farther its companion must be positioned, lest it merge with the primary. This is a frustrating problem and any progress towards its resolution is greatly appreciated.

Second, as far as I know modeling pulsars in Celestia is not technicaly doable at this time. I do not even believe there is a PSR reference in the program, is this (or will this) be remedied in future versions? Pulsars and Neutron stars, while distant and small are quite important and the ancient system mentioned above could use the addition. Also, are there any plans to account for different varieties of white dwarf. In celestia a generic "WD" marker is inserted for white dwarfs and the temperatre/color is fixed, in reality this is not so. Van Maanen's star is of a color/type close to F, while Sirius B has a color similar to a late B, early A type star. I know I brought up the idea of subtle color changes for main sequence stars in a previous post and since this idea is largely cosmetic, I don't believe it is at all pressing at this time.

I know Chris has worked on the radii calculation in Celestia, and form what I've seen his work has been good. However, are there, or will there ever be plans to allow the end-user, such as myself to specify mass or radius for the stars we are creating (where those values are known). Not that I mistrust the calculator itself, but since I'm obcessive about realism, I have to ask.

I would also inquire, are there any plans to allow for multiple lighting effects? I think I heard this requires a raytracer and if so it would require perhaps more time than its worth in the present state of development of Celestia. But, the Flammarion effect is real, and could be an interesting touch of realism for this excellent piece of software.

Finally, there is always the case of the infamous black hole, are such objects doable in Celestia as it is? or will there need to be further work done. A neat frame dragging effect would be super cool! ok well enough for now, good to talk to you guys. Adios.

Dunno about most of your questions, but there is an implementation of a pulsar system for Celestia - it's an addon (the zip file is psr1257.zip, but I can't remember where I got it from). It has the spinning lighthouse beam too, looks quite nice.

Apollo7 wrote:Ok so I'm sure you guys have heard of the Primeval planet, the 12.7 billion year old Juggernaut orbiting in a binary system where the primary is the star PSR B1620-26 a 1.35 MSol Pulsar, and the secondary is a .4 MSol white dwarf.

The planet orbits with a semimajor axis of 23 AU or so, and has about 2.5 Jupiter masses. I bring this system up for a couple of reasons. First its bizzare nature, and second, the possibility of modeling this system in future releases of Celestia.

Although my contributions to Celestia are now largely obsolete I have not lost interest in the medium. Moving away from school and being seperated from my computer for a very long time not withstanding, I'll be contributing again soon enough (I eagerly anticipate the release of v 1.3.1). Anyway enough ranting, here is the deal.

Has the "avoidance problem" I brought up in past posts, been fixed in V1.3.1 or will it be fixed in a future release. For those of you who do not know, one can only place a star so close to another star in Celestia before the two merge. Chris explained that this has something to do with the limits of detectability and observability from Earth. Apparently the greater distance a star is from Sol the farther its companion must be positioned, lest it merge with the primary. This is a frustrating problem and any progress towards its resolution is greatly appreciated.

The avoidance problem--or more correctly, the problem of using single precision floating point numbers for star position--has not been fixed yet. I have a solution in mind but have yet to implement it. What I want to do is add a new field to the star class which is a pointer to extra star data--an orbit, a custom appearance, etc. The companion star could then have the same position as the primary, but this would be modified by the orbit (only computed when you're close enough to the star or zoomed in far enough for it to make a difference.) I've been promising to do this for a long time

Another problem is that globular clusters are very far from Earth . . . such large distances also pose a problem when star positions are single-precision. The obvious solution of using double precision is problematic because of the extra memory usage it would incur.

Second, as far as I know modeling pulsars in Celestia is not technicaly doable at this time. I do not even believe there is a PSR reference in the program, is this (or will this) be remedied in future versions? Pulsars and Neutron stars, while distant and small are quite important and the ancient system mentioned above could use the addition. Also, are there any plans to account for different varieties of white dwarf. In celestia a generic "WD" marker is inserted for white dwarfs and the temperatre/color is fixed, in reality this is not so. Van Maanen's star is of a color/type close to F, while Sirius B has a color similar to a late B, early A type star. I know I brought up the idea of subtle color changes for main sequence stars in a previous post and since this idea is largely cosmetic, I don't believe it is at all pressing at this time.

It's not that hard to add the different white dwarf types . . . it's just one more thing I haven't gotten to yet.

I know Chris has worked on the radii calculation in Celestia, and form what I've seen his work has been good. However, are there, or will there ever be plans to allow the end-user, such as myself to specify mass or radius for the stars we are creating (where those values are known). Not that I mistrust the calculator itself, but since I'm obcessive about realism, I have to ask.

Via the same 'extended star info' mechanism that will be used for stellar orbits you'll also be able to override the computed radius.

I would also inquire, are there any plans to allow for multiple lighting effects? I think I heard this requires a raytracer and if so it would require perhaps more time than its worth in the present state of development of Celestia. But, the Flammarion effect is real, and could be an interesting touch of realism for this excellent piece of software.

What's the Flammarion effect?

Anyhow, no raytracing is required for multiple lights, and Celestia will eventually support this.

Finally, there is always the case of the infamous black hole, are such objects doable in Celestia as it is? or will there need to be further work done. A neat frame dragging effect would be super cool! ok well enough for now, good to talk to you guys. Adios.

The frame dragging effect is a ways off . . .

--Chris

chris wrote:

I would also inquire, are there any plans to allow for multiple lighting effects? I think I heard this requires a raytracer and if so it would require perhaps more time than its worth in the present state of development of Celestia. But, the Flammarion effect is real, and could be an interesting touch of realism for this excellent piece of software.

What's the Flammarion effect?

Anyhow, no raytracing is required for multiple lights, and Celestia will eventually support this.

IIRC the Flammarion effect is when you get two lightsources (usually of different colours) illuminating a surface. The picture I've seen (I can't remember where I saw it - I think it was in a space art book) was of a mountain or something on the planet's surface, illuminated by a red giant and a blue/white dwarf. You get two shadows of different colours cast by the mountain - where the red light is blocked and the blue light isn't, the 'shadow' is coloured blue, and vice versa. And where both lights are blocked, you get a black shadow.

Glad to hear Celestia will get the multiple light source eventually .

Ok well I think the Flammarion Effect got explained to a good degree so no problems there. Thanks again for the timely responses Chris.

So it sounds like once this extra-star data field is implimented that would be one step closer to actual stellar binary systems, is this correct?

I'd also like to pose another question. How is it in Celestia, that when I put a star in the exact same location as another star, say Epsilon Eridani, using the RA and Dec data directly from Celestia's data file, that the stars do not match up position wise, but are often seperated by many AU? How can using the same data result in a different outcome? Curious...

I wasn't refering to actually placing stars at globular cluster distance (7200 light years in the case of M4) just to the point of creating the system.

Also I've been thinking of adding in the missing extra solar planets (which now number over 110 into Celestia, but should I hold off until 1.3.1 is out?

Cheers.