Jättiläistähdet

Jättiläistähdet, known in English as giant stars, represent a significant evolutionary stage for stars. After exhausting the hydrogen fuel in their core, stars begin to fuse helium, causing their outer layers to expand dramatically. This expansion leads to a significant increase in their radius and luminosity, while their surface temperature decreases, giving them a cooler, redder appearance. The term "giant star" is a broad classification encompassing several specific types of stars that have undergone this expansion.

The most common type of giant star is the red giant. These stars are typically about 10 to 100 times the radius of our Sun. Our own Sun will eventually become a red giant in about 5 billion years, engulfing Mercury, Venus, and possibly Earth. Other types of giant stars include blue giants and luminous blue variables, which are generally hotter and more massive than red giants.

The formation of giant stars is a natural part of stellar evolution for stars with masses similar to or greater than our Sun. Smaller stars, like red dwarfs, are expected to remain on the main sequence for trillions of years and will not evolve into giant stars. The ultimate fate of a giant star depends on its initial mass. Less massive giant stars will shed their outer layers to form planetary nebulae, leaving behind a white dwarf. More massive giant stars can evolve into supergiants and eventually end their lives in supernova explosions. The study of giant stars provides crucial insights into stellar physics, nucleosynthesis, and the life cycles of stars in the universe.