Star Life Cycle Quiz

Study Notes

Birth: Protostars originate from the contraction of nebulae, which are clouds formed of dust, hydrogen, helium, and ionized gases.
Main Sequence: Approximately 90% of stars are in this phase, where they fuse hydrogen into helium in their cores. They vary significantly in size, ranging from one-tenth to 200 times the mass of the Sun.
Old Age: Stars expand as they age. When hydrogen and helium are depleted, their cores contract, while outer layers expand, cool, and dim, transforming into red giants or red supergiants based on initial mass. These stars exhibit high luminosity and low surface temperatures, typically below 5,000 K.
Death: Red supergiants, categorized under spectral types K or M, are the largest stars by volume. Notable examples include Betelgeuse and Antares. Upon exhausting their nuclear fuel, they can collapse and explode, leading to the formation of black dwarfs, neutron stars, or black holes, depending on their original mass.
Remnants: Low-mass stars evolve into planetary nebulae, creating a glowing shell of ionized gas. This process leads to the formation of a white dwarf, a dense remnant comprised mainly of electron-degenerate matter. These remnants can be as dense as the Sun but are comparable in size to Earth. Over time, a white dwarf can cool down to become a black dwarf, which emits negligible heat or light.