Explain the "life cycle" of a star using the terms listed in the image below.

Answer 1

To explain the life cycle of a star, we can break it down into several stages, incorporating common terms used in stellar evolution:

1. Nebula: The life cycle of a star begins in a nebula, which is a large cloud of gas and dust in space. Under the influence of gravity, parts of the nebula can collapse to form a dense region.

2. Protostar: As the material in the collapsing region gathers together, it forms a protostar. During this stage, the temperature and pressure at the core increase, but nuclear fusion has not yet started.

3. Main Sequence Star: When the core temperature becomes high enough (about 10 million degrees Celsius), hydrogen atoms begin to fuse into helium in a process called nuclear fusion. This stage is known as the main sequence, where the star remains for the majority of its life. Our Sun is currently in this phase.

4. Red Giant: Once the hydrogen in the core is depleted, the core contracts and heats up, leading to the outer layers of the star expanding and cooling, turning the star into a red giant. In this phase, the star may begin to fuse helium into heavier elements.

5. Supernova (for massive stars): If the star is massive enough, after the red giant phase, it may undergo a supernova explosion, leading to the creation of heavier elements and dispersing materials into space. This is a dramatic end to a massive star’s life.

6. Neutron Star or Black Hole: Following a supernova, if the remaining core is between about 1.4 to 3 times the mass of the Sun, it will collapse into a neutron star. If it is more than 3 times the solar mass, it will collapse into a black hole.

7. White Dwarf (for smaller stars): In contrast, stars with a mass similar to the Sun will shed their outer layers and leave behind a hot core that becomes a white dwarf. Over billions of years, this white dwarf will cool and fade away.

8. Planetary Nebula: The outer layers of the smaller stars that are ejected during this process create a planetary nebula, which is a colorful shell of gas that surrounds the white dwarf.

9. Stellar Remnants: Ultimately, the remnants of the star’s material, either as white dwarfs, neutron stars, or black holes, can contribute to the formation of new stars, starting the cycle again.

Through these stages, stars evolve, create new elements, and influence their surroundings, contributing to the dynamic nature of the universe.