Final answer:
A system of stars, gas, dust, and dark matter bound together by gravity is called a galaxy, like the Milky Way, which contains enough matter to make billions of stars and significantly more dark matter than luminous matter.
Step-by-step explanation:
A system of stars, gas, dust, and dark matter bound together by gravity is called a galaxy. Galaxies, such as the Milky Way, contain enormous amounts of gas and dust, enough to make billions of stars like the Sun. While the number of stars we can observe is vast, it may only be a small fraction of the original matter created in the Big Bang. Dark matter is inferred by phenomena such as the gravitational lensing of light from distant galaxies, suggesting there is significantly more mass present than what we can directly observe. Additionally, a galaxy can contain up to ten times more dark matter than the luminous matter we can detect, which includes stars, gas, and dust.