Essential Questions:
- What is the relationship between ,ass and a star’s evolution?
- What are the features of massive and regular star life cycles?
- How is the universe affected by the life cycles of a star?
Vocabulary:
nebula
protostar
neutron star
pulsar
supernova
black hole
Basic Structure of Stars
Mass governs a star’s temperature, luminosity, and diameter. Mass and composition determine nearly all of a star’s other properties.
Mass Effects
The more massive the star, the greater the gravity pressing inward
A star maintains its size due to hydrostatic equilibrium. This is maintained by gravity pushing in equally against the outward pressure from heat and nuclear reactions inside the star.
Fusion
Density and temperature increase toward the center of a star. Nuclear fusion, which occurs in the star’s center, generates energy. Main sequence stars fuse hydrogen into helium.
Stellar Evolution
Life cycle of a Medium mass star
Protostar
A developing star, not yet hot enough for nuclear fusion to occur
https://en.wikipedia.org/wiki/Protostar
Main sequence star
https://upload.wikimedia.org/wikipedia/commons/8/8b/Morgan-Keenan_spectral_classification.png
Core temp is at least 10 million K and nuclear fusion occurs
Star is a stable size as gravity pushing in is offset by gas pressure pushing out
Red Giant
All hydrogen in core gets consumed so star collapses causing the temp. to increase
Forms b/c zone of nuclear fusion moves outward
Planetary Neblua
During the collapse from a red giant to a white dwarf, a glowing cloud of gases is emitted
White dwarf
Remains of low and medium mass stars
Extremely small star w/ density greater than any substance on Earth
Black dwarf
A white dwarf that has cooled such that it is no longer emitting light