Sorry... This has all the necessary criterion...

The Milky Way is a barred spiral galaxy of a Local Group of galaxies within the Virgo Supercluster. The main disk of the Milky Way Galaxy is about 80,000 to 100,000 light-years in diameter, about 250,000 to 300,000 light-years in circumference, and outside the Galactic core, about 1,000 light-years in thickness. The galaxy is estimated to contain 200 billion stars but this number might reach 400 billion if small-mass stars predominate. As a guide to the relative physical scale of the Milky Way, if the galaxy were reduced to 130 km (80 mi) in diameter, the solar system would be a mere 2 mm (0.08 inches) in width.

If life can be found circulating 1 in 187,346 of these stars, using the estimate of 200 billion, how long would these 'other' star systems extend (in millimeters) if they were stuck end to end on a continuous line... if the Milky Way galaxy were reduced to 20 miles (32.5 km) in diameter, and we assumed (for simplicity's sake) that all the star systems were equal in size to our very own Solar system?
ttr