The source of energy that keeps the Sun shining today is
nuclear fusion
Which of these layers of the Sun is coolest?
photosphere
This X-ray image shows a loop of hot gas above the surface of the Sun. Surface features on the Sun like these are what kind of phenomena?
magnetic
This figure represents the equilibrium achieved in a star between a pull inward and a push outward. What causes these pushes and pulls?
The pull inward is due to gravity and the push outward is due to a radiation pressure from fusion.
Why is a star's birth mass its most fundamental property?
A star's birth mass is the most important predictor of a star's lifetime. A star born with high mass will have a short lifespan; a star born with low mass will have a significantly longer lifespan.
How is the lifetime of a star related to its mass?
More massive stars live much shorter lives than less massive stars.
What is the common trait of all main-sequence stars?
They generate energy through hydrogen fusion in their core.
After a star runs out of Hydrogen fuel in the core, in order to fuse Helium what must happen first?
gravity must shrink the star and raise the core temperature