the universe is still cooling from the initial explosion.

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

All of the matter and energy in space known existence

This isthe study of the universe and everything within it

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.

demonstrates the idea that the universe is contracting

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

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)

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

The distance that light travels in a year

spheres of gas in space that produce their own energy (self luminous - provide their own light source)

provides evidence that the universe is still expanding.

this is the stable period, early stage, creates energy and shines bright. Our sun is in the main sequence stage.