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

Question

Life Cycle of a Star Timeline
Terms to include:
White Dwarf
Main Sequence
Red Giants
Super Giants
Supernova
Nebula
Black Hole
Short Answer Rubric (4 points)

Answer 1

The life cycle of a star can be divided into several key stages, each marked by significant changes and evolution in the star's structure and energy generation processes. Here’s an overview:

1. Nebula: The life of a star begins in a nebula, which is a vast cloud of gas and dust in space. Under the force of gravity, the particles in the nebula start to clump together, eventually forming a protostar.

2. Main Sequence: Once the protostar has gathered enough mass and temperature to initiate nuclear fusion in its core, it enters the main sequence phase. During this prolonged stage, the star fuses hydrogen into helium, maintaining a stable balance between gravitational forces and the outward pressure generated by nuclear fusion. Our Sun is currently in this phase.

3. Red Giants: After millions to billions of years in the main sequence, the star exhausts its hydrogen fuel. It begins to fuse helium and other heavier elements, expanding and cooling in the process. This phase is known as the red giant stage. The star's size increases significantly, becoming much larger and redder.

4. Super Giants: If the star is particularly massive, it may evolve into a supergiant after the red giant stage. In this phase, the star fuses heavier elements in its core, leading to further expansion and increased luminosity. Supergiants can have lifetimes of just a few million years compared to their smaller counterparts.

5. Supernova: When a massive supergiant runs out of nuclear fuel, it can no longer support itself against gravitational collapse. This leads to a catastrophic explosion known as a supernova, which can outshine entire galaxies for a short period and disperses heavy elements into space.

6. Black Hole or White Dwarf: The remnants of a supernova can result in either a neutron star or a black hole, depending on the mass of the original star. For less massive stars, the remnants become a white dwarf, a dense core left over after the outer layers have been expelled. The white dwarf will eventually cool and fade away.

This cycle illustrates the complex processes that govern stellar evolution and how stars contribute to the cosmic ecosystem by recycling matter and energy throughout the universe.