1. Red Giant Phase: In about 5 billion years, the Sun will run out of hydrogen fuel in its core. It will begin to fuse heavier elements like helium, causing its core to contract and its outer layers to expand dramatically. This expansion will turn the Sun into a red giant, engulfing Mercury, Venus, and potentially Earth.
2. Helium Flash: As the core collapses, it will reach a point where helium fusion ignites explosively in a process called the helium flash. This releases a tremendous amount of energy, but it's a relatively short-lived event.
3. Asymptotic Giant Branch: The Sun will then enter the asymptotic giant branch (AGB) phase. It will continue fusing heavier elements, experiencing periods of instability and losing mass through strong stellar winds.
4. Planetary Nebula: Eventually, the Sun's outer layers will be ejected into space, forming a colorful shell known as a planetary nebula. This nebula is not related to planets, but rather gets its name from its round, planet-like appearance through early telescopes.
5. White Dwarf: At the center of the planetary nebula, the Sun's core will be left behind as a white dwarf. This is a very dense, hot, and small remnant of the Sun's core. White dwarfs are about the size of Earth but contain roughly the same mass as the Sun. They will gradually cool and fade over trillions of years, eventually becoming black dwarfs.
Important Note: The Sun is not massive enough to become a supernova or a black hole. It lacks the gravitational pull required for those events, which are typically associated with stars much larger than our Sun.
