Which description matches a system of stars, stellar remnants, interstellar gas, dust, and dark matter bound together by gravity?

Which description matches a system of stars, stellar remnants, interstellar gas, dust, and dark matter bound together by gravity?

• A. Galaxy
• B. Lunar
• C. Gravitational forces
• D. White dwarf

Answer: (A)

A galaxy is a gravitationally bound collection that includes many components: stars in various life stages, stellar remnants, vast swaths of interstellar gas and dust, and dark matter that forms an invisible halo. The gravity of all these parts holds the whole system together over billions of years and shapes how stars and gas move inside it. Dark matter is key because it adds mass without emitting light, helping explain why galaxies remain cohesive instead of dispersing. This description matches a galaxy. The Moon is a single object orbiting Earth, gravitational forces refer to the interaction between masses rather than a bound system, and a white dwarf is just a single stellar remnant, not a large bound structure containing gas, dust, and dark matter.

A galaxy is a gravitationally bound collection that includes many components: stars in various life stages, stellar remnants, vast swaths of interstellar gas and dust, and dark matter that forms an invisible halo. The gravity of all these parts holds the whole system together over billions of years and shapes how stars and gas move inside it. Dark matter is key because it adds mass without emitting light, helping explain why galaxies remain cohesive instead of dispersing. This description matches a galaxy. The Moon is a single object orbiting Earth, gravitational forces refer to the interaction between masses rather than a bound system, and a white dwarf is just a single stellar remnant, not a large bound structure containing gas, dust, and dark matter.