EVERYDAY SCIENCE

Detailed explanation-1: -Galaxies are vast cosmic islands of stars, gas, dust, and dark matter held together by gravity.

Detailed explanation-2: -Nebulae are made of dust and gases-mostly hydrogen and helium. The dust and gases in a nebula are very spread out, but gravity can slowly begin to pull together clumps of dust and gas.

Detailed explanation-3: -Our galaxy, the Milky Way, is typical: it has hundreds of billions of stars, enough gas and dust to make billions more stars, and at least ten times as much dark matter as all the stars and gas put together. And it’s all held together by gravity.

Detailed explanation-4: -Answer. Because this grouping includes stars, it would be called a galaxy. Compare this to a nebula, which also incorporates gas and dust held together by gravity.