I think it's one of the best graphically and scientifically accurate space emulators.
Latest blog post of development of SE 0.981
http://spaceengine.org/news/blog170729/
>''With 0.981, SE will be the first game engine which generates physically-accurate planets. The new model is also enables modelling of the planet’s internal structure: it is possible to calculate at which radius the iron core transitions into the silicate mantle, and what temperature, pressure and density are there. I am not sure this will be in 0.981 though...''
New volumetric nebulae are being added in this version, along with graphic updates, new planetary classification/generation and VR.
New integration of volumetrics...
Some screenshots from 0.980 and 0.981.
>non-free software