refers to the brightness of a star, which is determined by the size of the star. The larger the star, the more luminous it is. The smaller the star, the less luminous it is.

A large system of stars, gas, dust, and dark matter held together by gravity. Usually in a spiral shape, with our solar system at the end of the spiral.

the process by which stars produce their own energy. Hydrogen atoms combine with helium atoms to form a star.

provides evidence that the universe is still expanding.

stars all begin as large spinning clouds of gas and dust being pulled together by the force of gravity.

the universe is still cooling from the initial explosion.

intermediate stage of its life. The star is getting larger and is more luminous.

All of the matter and energy in space known existence

This isthe study of the universe and everything within it

the apparent change in wavelength of an energy source that is moving (for example: waiting at a train platform and listening to the train get louder as it passes you and quieter once it is past you completely)

late stage, where the star will become much hotter, smaller and less luminous.

The distance that light travels in a year

demonstrates the idea that the universe is contracting