GENERAL KNOWLEDGE

Detailed explanation-1: -A huge collections of stars, dust and gas are known as galaxies. They contain several million of stars and their size can range from few thousands to several hundred thousands light years. They have different shapes and brightness and can be found alone, in pairs or in clusters. The galaxy of Earth is called Milky Way.

Detailed explanation-2: -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-3: -A nebula is a giant cloud of dust and gas in space. Some nebulae (more than one nebula) come from the gas and dust thrown out by the explosion of a dying star, such as a supernova. Other nebulae are regions where new stars are beginning to form. For this reason, some nebulae are called “star nurseries."

Detailed explanation-4: -star cluster, either of two general types of stellar assemblages held together by the mutual gravitational attraction of its members, which are physically related through common origin. The two types are open (formerly called galactic) clusters and globular clusters.