Size Milky Way

The stellar disk of the Milky Way galaxy is around 100,000 light-years in diameter, and is supposed to be, on average, about 1,000 ly thick. It is estimated to contain at least 200 billion stars and probably up to 400 billion stars, the exact figure depending on the number of very low-mass stars, which is highly uncertain. Extending past the stellar disk is a much thicker disk of gas. Recent observations designate that the gaseous disk of the Milky Way has a width of around 12,000 ly twice the previously established value. As a guide to the relation physical scale of the Milky Way, if it were condensed to 130 km in width, the Solar System would be a mere 2 mm in width.

The Galactic Halo extend outward, but is limited in size by the orbits of the two Milky Way satellites, the Large and the Small Magellanic Clouds, whose perigalacticon is at 180,000 ly .