In the universe there are many types of stars. They come in many sizes, temperatures, and colors, ranging from cooler, small M class (red) stars to large, hot O class (blue). The mass of a star is what determines its “life” cycle. Smaller stars tend to burn out silently while larger stars usually end in a supernova. However the stuff they leave behind can be quite interesting, and there are many hypothetical types of stellar remnants.
The first 2 types of stars are blue dwarves and black dwarves. These are the later stages of what happens to a red dwarf. According to Smithsonian Magazine “astronomers believe red dwarfs can last for trillions of years”. This means they can be almost as old as the universe itself (13.8 billion years) and still have a long way to go before becoming a blue dwarf, the hypothetical final stage of a red dwarf before it becomes a white dwarf. All smaller mass stars, meaning those not large enough to go supernova, are hypothesized to end up as a black dwarf once their white dwarf stage runs out of fuel.
The next type of star is a quark star. They are made entirely of either quark matter or strange matter. Quarks are what make up all the elements and come in 6 different types; up, down, charm, strange, top, and bottom. Quark stars are formed when a neutron star is put under enough pressure that the neutrons that make it up collapse into quarks. What sets them apart from regular neutron stars is that they behave as a fermi liquid and enter a color-flavor-locked state of color superconductivity, which is all very complicated stuff.
The last type of star is a white hole. They are the exact opposite of a black hole, ejecting matter rather than absorbing it. If you were to see one, it could be described as a “a video of a black hole played backwards”. They would hypothetically form after a black hole decays enough, releasing all information (meaning stuff that fell into it) that it gathered previously, but this process would take many trillions of years. Almost everything involving white holes is mysterious and complicated and as of yet they are a hypothetical object.