In the book Mass Effect: Retribution on the first page the answer to this forum is found.
The Illusive Man sat in his chair, staring out the
viewing window that formed the entire outer wall of
his inner sanctum.
The unnamed space station he used as his base was
orbiting a red giant-class M star. The semispherical
edge of the burning sun filled the entire lower half of
the viewing window, its brightness dominating but
not completely obscuring the field of the stars behind it.
The star was in the last stages of it six-billion-year
life span. As the grand final act culminatin it existence, it would collapse in upon itself,
creating a black hole to swallow the entire system. The planets
and the moons it had spawned in its birth would be devoured
in the inescapable gravitational pull of the dark, gaping maw left behind by its death.
the scene encapsulated everything the Illusive Man believed about the galaxy:
it was beautiful, glorious and deadly, Life could spring up in the least
likely of places in the most unimaginable of forms, only
to be snuffed out in a blink of the cosmic eye.