Fusion & Balance
This process joins hydrogen nuclei to form helium and releases energy.
What is nuclear fusion?
These two properties are compared on an H-R diagram.
What are surface temperature and luminosity?
This is the long, stable stage when a star fuses hydrogen in its core.
What is the Main Sequence?
A massive star’s collapsing core may lead to this powerful explosion.
What is a supernova?
Hydrogen nuclei join together in a star to form this element.
What is helium?
This force squeezes a star’s material inward toward its center.
What is gravity?
This stellar property is plotted on the horizontal axis.
What is surface temperature?
When hydrogen in a star’s core runs low, the core does this.
What is contraction?
The released outer layers of an average-mass star form this.
What is a planetary nebula?
Name two heavier elements the reading says very massive stars can form after helium.
What are any two of carbon, oxygen, neon, and iron?
This outward push from energy made by fusion balances gravity in a stable star.
What is pressure from fusion, or fusion pressure?
The hottest stars appear in this location on the H-R diagram.
Where is the left side of the temperature axis?
At the same time the core contracts, the star’s outer atmosphere does these two things.
What are expand and cool?
This hot core, about the size of Earth, remains after an average-mass star releases its outer layers.
What is a white dwarf?
This event sends newly formed elements from a massive star into space.
What is a supernova explosion?
For about this fraction of a star’s life, gravity’s inward pull is balanced by pressure from fusion pushing outward
What is about 90 percent?
As you move from left to right along the temperature axis, stars become this.
What is cooler?
After core hydrogen runs low and the outer atmosphere expands and cools, a star may become one of these.
What is a bright red giant or supergiant?
When iron builds up in a massive star’s core, fusion stops because fusing iron does this to energy.
What is absorb energy instead of releasing it?
The newly formed elements sent into space by a supernova may become part of these later.
What are future planets and other objects?
Explain how fusion energy is connected both to a star’s stability and to the light and heat that travel through space.
Fusion energy creates outward pressure that balances gravity, and energy moves outward and travels through space as light and heat.
These hot stellar cores have low luminosity and appear near the lower-left of the H-R diagram.
What are white dwarfs?
Use the reading to describe how a star changes after core hydrogen runs low. Include the change in the core and the outer atmosphere.
The core contracts while the outer atmosphere expands and cools; the star may become a red giant or supergiant.
Compare the ending of a massive star with the ending of an average-mass star like the Sun.
A massive star’s core may collapse and lead to a supernova that sends elements into space. An average-mass star releases its outer layers as a planetary nebula and leaves a white dwarf.
Explain how a massive star’s life can help spread heavier elements through space.
Very massive stars form heavier elements through fusion; when the core collapses and the star explodes as a supernova, the explosion sends newly formed elements into space.