Space GapFill

Stars are formed in huge clouds of gas and dust called  main sequence starsnebulaewhite dwarfsneutron starssupernovaeblack holes. These clouds are much denser than the vast majority of space, but are still much less dense than even the best vacuums ever created on Earth! Over time, these clouds can come together via  gravityfusionfissionmagnetismrandom chanceelectrostatic forces to create large masses such as asteroids, planets, moons and stars. If large enough, these large masses can become stars - but they are only protostars until the pressures and temperatures at their centres become high enough for the stars to start releasing energy via  fusion of heavy elementsdoing workfusion of light elementsmagnetismfission of heavy elementsfission of heavy elements. Once a star begins shining, it is considered a  main sequence starwhite dwarfnebulablack holesupernovaneutron star, where it spends most of its lifetime - our Sun is in this stage of its life cycle.
The next stage in a star's life cycle depends on the star's  agebrightnesscolourcompositionmasstemperature. Some, like our Sun, will become red giants, where they expand massively - when our Sun becomes a red giant billions of years in the future, it will become large enough to swallow Earth. Eventually these red giants shed their outer layers, leaving behind their hot core, known as a  nebulablack holeneutron starmain sequence starsupernovawhite dwarf - eventually these will cool down and stop glowing, but they are so hot that this takes longer than the current age of the universe, so no cooled-down cores like this yet exist!
Other stars become red supergiants, which are significantly larger than red giants. When these run out of all fuel, they collapse and then explode in what are known as  neutron starsnebulaewhite dwarfssupernovaeblack holesmain sequence stars - these are the brightest objects in the universe, and the source of all the elements with  higher masses than leadlower masses than leadlower masses than ironhigher masses than ironhigher masses than uraniumlower masses than uranium throughout the universe. The objects left over can be either  neutron starsnebulaeblack holesmain sequence starssupernovaewhite dwarfs, which are so dense that protons and electrons are forced together in their cores, or  neutron starsmain sequence starswhite dwarfsnebulaesupernovaeblack holes, which have such high gravity that nothing can escape them - not even light.
All of the objects in our solar system - suns, planets, moons and artificial satellites - move around each other in patterns known as  arcsgalaxiescentrifugesretrogradesorbitsloops, which are dictated by gravity.
As scientists' understanding of the universe grew, they noticed something strange - stars and galaxies that were further away had wavelengths that were longer than expected, an effect known as  orbitinggravitational wavesthe Big Banglight stretchingred-shiftblue-shift. This implies that all of the galaxies are moving away from each other, and were once much closer together; called the  inflationblue-shiftBig Bangred-shiftexpansionDoppler theory. But there is still a lot for scientists to understand; many scientists believe we can only see around 5 % of all the mass and energy in the universe, with the rest being  Higgshyperexoticquantumblackdark mass and energy.