in the course of my ongoing Celestia.Sci
development, I also implemented a sophisticated, entirely new simulation of globular clusters. It incorporates the state of the art of understanding the evolution of globular star populations. As soon as I find some more spare time, I'll document here what went in. One main aim was to visualize correctly the subtle star colors in addition to the proper spacial cluster structures. The rendering both of normal (isolated) stars and globular cluster stars is done with the same shader
code. Also, the mapping of the effective temperatures (T_eff) to RGB colors is the same for all
Let me report here on a cute "Gedanken experiment":
Imagine our solar system was part of a globular cluster!
What I did, was to copy from globulars.dsc the data of the famous globular 47 Tuc (NGC 104)
with a couple of changes:
Globular "SolGlob 1"
RA 0.4014 # [hours]
Dec -72.0811 # [degrees]
Distance 15.0 # [ly]
Radius 109.3 # [ly] from refit to King62 profile
CoreRadius 496.9 # [arcmin]
KingConcentration 1.94 # from refit to King62 profile
AbsMag -9.42 # [V mags]
VminusI 1.14 # V-I colour index
Axis [ -0.7429 -0.2364 -0.6263]
Angle 175.9 # [degrees]
I called the new ficticious globular SolGlob 1
and merely adapted the distance and --for consistency-- the angular size of the CoreRadius of 47 Tuc:
The μ25 radius of 47 Tuc is 109 ly. So, after some experimentation, I placed the center of SolGlob 1 just 15 ly from the solar system barycenter
! This is quite a difference to the original distance of 14680 ly! For the original distance of 47 Tuc, the angular
CoreRadius was just 0.5087 arcmin. Since the distance of SolGlob 1 is now much smaller, the angular size must correspondingly increase a lot in order to retain the same CoreRadius in [ly]. The respective formula is simple:
CoreRadius_SolGlob 1 [arcmin] = 60 * 2 * atan(d_47 Tuc / d_SolGlob1 *
tan(CoreRadius_47 Tuc[arcmin] /(60 * 2) ) )
This gives the above value of 496.9 arcmin instead of only 0.5087 arcmin.
It means that just the core of SolGlob 1 now covers an angular region of 16.6 degrees in the sky
. This amounts to 32 Full Moons...
So let's have a look at some typical views that we would have from space just behind Earth, from the surface of Earth and from the Moon, say (no atmosphere). Of course, one could as well have placed some ficticious "solar system" with planets into any given globular cluster...
The SolGlob 1 globular cluster simulation involves about 100 000 stars...
View from space, just behind the Earth:
Next, I went to the Earth surface, left atmosphere and clouds on. Then you get this amazing view in the evening twilight:
Finally, from the surface of a body without atmosphere (Moon) the view is also spectacular:
I think this shot provides a feel about what it might be like to live amidst a rich star cluster, just 15 ly away from its center