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**	\field spin		blackhole spin rate, in seconds per 360 degrees turns.
**				if set to 0.0, a Schwarzschild blackhole is assumed.
**				otherwise, it is treated as a Kerr blackhole.
**	\field charge		FIXME: mmh... we don't really care about this (yet...)
**
**	the blackhole mass is grabbed directly from the en_space base node
**
**	FIXME: should we have partial blackholes? partial on the appearance point of view at least?
**	large neutron stars whose gravity hasn't become strong enough to overcome the strong nuclear force
**	holding neutrons apart and stopping a further gravitational collapse.
**	for these bodies, the event horizon might still be below the star's surface, but the photon sphere
**	may be above (1.5 schwarzschild/event radii). if that's the case, the star will have a very special appearance. light will bend around it
**	and space will appear deformed, as with a blackhole, but a small center part of the star will still
**	be visible...
**
**	so here we have three possible states:
**	- star:	both the event horizon and the photon sphere are below the star's surface: regular rendering,
**		light bends around the star, perhaps dramatically, but no blacked-out parts...
**
**	- partial blackhole: the event horizon is still below the star's surface, but the photon sphere is now above.
**			     there is a partial blackout around the star, and the percentage of it that stays visible
**			     depends on where the photon sphere and event horizon are located.
**			     if the photon sphere is right on the surface, every part of the star is visible.
**			     if the event horizon is right on the surface, not a single part can be seen...
**			     between the two, we will have the impression of a blackhole that has a circular window
**			     on its center that allows us to see the star beneath. the closer the event horizon gets
**			     from the surface, the smaller the window. the closer the photon sphere gets to the
**			     surface, the larger the window.
**
**	- blackhole: both the photon sphere and the event horizon are above the star's surface...
**		     the body becoming an apparent blackhole does NOT imply that the whole star's matter collapsed
**		     into an hypothetical singularity (that means a finite mass collapsed into a null volume,
**		     that has an infinite density... absurd... (but we don't care here anyway, the only radius we
**		     will store in the celestial node for this object is the schwarzschild radius)).
**
**
**	FIXME2: perhaps we should account for visual/spatial deformation for all stars. except we probably
**		almost never need to render a dual paraboloid map to simulate light bends for regular stars.
**		copying the backbuffer without the star into a texture, and indexing this texture with
**		bent light rays should suffice... it will break down for objects very close to the star, but the
**		visual artifacts will probably be insignificant and unnoticeables...