GENERAL KNOWLEDGE

Detailed explanation-1: -This mysterious stuff is called “dark matter.” The stars and gas we see make up less than 10 percent of the mass of a galaxy.

Detailed explanation-2: -The total mass of the Galaxy is about 2×1012 MSun. As much as 95% of this mass consists of dark matter that emits no electromagnetic radiation and can be detected only because of the gravitational force it exerts on visible stars and interstellar matter.

Detailed explanation-3: -It turns out that, at four percent, gases make up a much bigger part of the cosmos. They usually occupy the space between stars, and for that matter, the space between whole galaxies.