When stars reach the end of their lives, what happens to them depends on how big they were when they started. This journey through their life cycle leads to five main endings based on their size. Here's a simple breakdown:

1. Low-Mass Stars (like the Sun):

   • What Happens: These stars are not super huge, with masses up to about 2-3 times that of our Sun.
   • Ending: They eventually become white dwarfs after a long time.
   • Fun Fact: Our Sun is currently a main sequence star. In about 5 billion years, it will change into a red giant, lose its outer layers, and leave behind a white dwarf.
   • Temperature: When white dwarfs first form, they’re really hot, around 100,000 K. But they cool down slowly over billions of years.

2. Intermediate-Mass Stars:

   • What Happens: These stars are a bit bigger, with masses up to about 8 times that of our Sun.
   • Ending: They can create beautiful planetary nebulae and also end up as white dwarfs.

3. High-Mass Stars:

   • What Happens: These stars are much larger, over 8 times the mass of our Sun. They go through some exciting changes and can fuse heavier elements all the way up to iron.
   • Ending: At the end of their lives, they explode in a big boom called a supernova.
   • Possible Outcomes:
     • Neutron Stars: These form from the supernova explosions of stars with masses between about 8 and 20 times that of the Sun.
     • Black Holes: If a star is super massive (more than about 20 solar masses), its core collapses and can create a black hole.

4. Stellar Remnants:

   • Neutron Stars: These are about 1.4 times the mass of the Sun but are very tiny—only about 10-12 km across. They are incredibly dense.
   • Black Holes: These have a boundary called an event horizon, and they can be very massive without limits. They form when a star collapses after a supernova.

In conclusion, what happens to stars when they die depends on their size. They can become white dwarfs, neutron stars, or black holes. Each of these endings shows how gravitational and nuclear forces shape their lives.