Can't precisely center "Nebulae"
Posted: 15.07.2003, 11:04
This bug is in Celestia v1.3.1pre6 and earlier.
When a Nebula is declared to be precisely centered on the Solar System, it winds up over 200AU away. It'd be useful if this offset could be eliminated.
For example,
When the viewpoint is near the Sun, Celestia displays a distance of 206.395AU for "OortCloud" instead of some 10K kilometers.
(Of course, I need to choose a different [empty?]name for the object's centroid.)
Also, if one accepts that distance offset, when one "centers" OortCloud, the viewpoint looks toward 12h, 0 deg instead of toward 0,0.
Comments for those interested in the astronomical background:
This project wound up rather more complicated than I expected, which is why I haven't provided the model yet. It turns out that the outermost limit of the Oort isn't speherical at all. It's more like an ellipsoid. (I haven't found the articles that actually describe its shape, yet.) Most of the longest period comets are deflected in toward the sun due to galactic tidal forces: no specific perturbing objects are needed to account for their rate of "production". Also, current indications are that the "Halley type comets" originate from a region near the plane of the ecliptic and much closer to us than the main body of the cloud. There seem to be problems with the details of the proposed model, though.
When a Nebula is declared to be precisely centered on the Solar System, it winds up over 200AU away. It'd be useful if this offset could be eliminated.
For example,
Code: Select all
Nebula "OortCloud" {
Mesh "oort-2.3ds"
RA 0.0
Dec 0.0
Distance 1.0e-31
Radius 0.7 # 44000 au: 1 ly = 63240 au
InfoURL "http://berlinadmin.dlr.de/SGF/acm2002/abstracts/pshort/10-09p.pdf"
}When the viewpoint is near the Sun, Celestia displays a distance of 206.395AU for "OortCloud" instead of some 10K kilometers.
(Of course, I need to choose a different [empty?]name for the object's centroid.)
Also, if one accepts that distance offset, when one "centers" OortCloud, the viewpoint looks toward 12h, 0 deg instead of toward 0,0.
Comments for those interested in the astronomical background:
This project wound up rather more complicated than I expected, which is why I haven't provided the model yet. It turns out that the outermost limit of the Oort isn't speherical at all. It's more like an ellipsoid. (I haven't found the articles that actually describe its shape, yet.) Most of the longest period comets are deflected in toward the sun due to galactic tidal forces: no specific perturbing objects are needed to account for their rate of "production". Also, current indications are that the "Halley type comets" originate from a region near the plane of the ecliptic and much closer to us than the main body of the cloud. There seem to be problems with the details of the proposed model, though.