Identifying Large Cosmic Structures

The question asks us to identify the term that describes a very large collection containing gas, dust, and billions of stars.

Let's examine the options provided:

• Solar system: A solar system consists of a star and all the celestial bodies that orbit it due to gravity, such as planets, moons, asteroids, comets, and dust. Our own solar system includes the Sun and everything orbiting it. While it contains gas and dust, it centers around a single star (or a few in some cases) and its orbiting objects, not billions of stars.
• Satellite: A satellite is an object that orbits a larger celestial body. Examples include natural moons orbiting planets or artificial spacecraft orbiting Earth. A satellite is a single object, not a collection of billions of stars, gas, and dust.
• Galaxy: A galaxy is a massive system of stars, stellar remnants, interstellar gas, dust, and dark matter, all bound together by gravity. Galaxies are truly enormous and typically contain billions, or even trillions, of stars. Our Sun is just one of hundreds of billions of stars in our galaxy, the Milky Way. The description in the question perfectly matches the definition of a galaxy – a huge collection of gas, dust, and billions of stars.
• Planet: A planet is a large celestial body that orbits a star, has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and has cleared the neighbourhood around its orbit. A planet is a single body orbiting a star, not a collection of billions of stars.

Based on the definitions, the term that describes a huge collection of gas, dust, and billions of stars is a galaxy.