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Giant Stages – Low Mass Stars. Main Sequence Red Giant. At the center, Hydrogen is gone – there is only Helium “ash” As more Helium accumulates, gravity pulls the core together – it shrinks and heats up Hydrogen continues to burn in a layer around the center - PowerPoint PPT Presentation
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Main Sequence Red Giant•At the center, Hydrogen is gone – there is only Helium “ash”•As more Helium accumulates, gravity pulls the core together – it shrinks and heats up•Hydrogen continues to burn in a layer around the center
•High temperature – it burns fast•Luminosity rises
•This dumps lots of heat into the outer layer•It expands and cools
•Molecular Cloud•Protostar•Main Sequence•Red Giant•Core Helium-Burning•Double Shell-Burning•Planetary Nebula•White Dwarf
Giant Stages – Low Mass Stars
HydrogenHelium
Main Sequence Red Giant•Molecular Cloud•Protostar•Main Sequence•Red Giant•Core Helium-Burning•Double Shell-Burning•Planetary Nebula•White Dwarf
Main SequenceRed Giant
Red Giant•Molecular Cloud•Protostar•Main Sequence•Red Giant•Core Helium-Burning•Double Shell-Burning•Planetary Nebula•White Dwarf
•Star moves up and right on H-R diagram
Core Helium-Burning
Double Shell-Burning
Red Giant•The star is incredibly bright and incredibly large
•Goodbye Mercury•It is using up fuel faster than ever
•It evolves fast•200 Myr for Sun
•The core keeps getting more massive, more compressed, and hotter
•It accelerates faster and faster
•Molecular Cloud•Protostar•Main Sequence•Red Giant•Core Helium-Burning•Double Shell-Burning•Planetary Nebula•White Dwarf
An Aside: Some Nomenclature Issues•Astronomers use different names for the same thing•My old tests, and occasional diagrams, use alternate names:
New Names: Old Names:Core Helium-Burning Horizontal BranchDouble Shell-Burning Asymptotic BranchMassive Star Supernova Type II SupernovaWhite Dwarf Supernova Type I Supernova
More Nuclear Physics•There are other processes besides Hydrogen burning•At 100 million K, three Heliums can join to make carbon plus a little energy
3He C + Energy•With a little higher temperature,they can add one more to makeoxygen
C + He O + Energy
•These processes produce farless energy than hydrogen burning
Red Giant Core Helium Burning •Molecular Cloud•Protostar•Main Sequence•Red Giant•Core Helium-Burning•Double Shell-Burning•Planetary Nebula•White Dwarf
•At 100 million K, the helium core in a red giant star ignites
•Suddenly for light stars (< 3 MSun)
•Gradually for heavy stars (> 3 MSun)•New heat source in core
•It expands and cools•Hydrogen, still burning in a shell, burns more slowly now
•Less heat going into hydrogen envelope•Hydrogen envelope shrinks and heats up
•Star moves down and left on H-R diagram
Red Giant Core Helium Burning •Molecular Cloud•Protostar•Main Sequence•Red Giant•Core Helium-Burning•Double Shell-Burning•Planetary Nebula•White DwarfHydrogen
HeliumCarbon/Oxygen
Red GiantCore Helium- Burning
Core Helium Burning •Molecular Cloud•Protostar•Main Sequence•Red Giant•Core Helium-Burning•Double Shell-Burning•Planetary Nebula•White Dwarf
•Star gets hotter and dimmer
Core Helium-Burning
Double Shell-Burning
Core Helium Double Shell Burning •Molecular Cloud•Protostar•Main Sequence•Red Giant•Core Helium-Burning•Double Shell-Burning•Planetary Nebula•White Dwarf
•The star is burning Helium to Oxygen and Carbon•It doesn’t produce much energy – Helium gets used up fast•Eventually, Helium is completely used up and we have a Carbon/Oxygen core left
•50 Myr for the Sun•The star enters Double Shell-Burning
Double Shell Burning •The Core consists of Carbon/Oxygen ash
•It grows more massive over time •Heat is leaking out of it
•It gets smaller and hotter•Helium and Hydrogen burning accelerate
•Lots of energy dumped in outer layers•Star gets big, cool, and luminous•Bye bye Venus and maybe Earth
•Star gets brighter than ever•Up and to the right again on H-R diagram
•Molecular Cloud•Protostar•Main Sequence•Red Giant•Core Helium-Burning•Double Shell-Burning•Planetary Nebula•White Dwarf
Core Helium- Burning
Double Shell- Burning
Core Helium- Double-Shell Burning
HydrogenHeliumCarbon/Oxygen
•Molecular Cloud•Protostar•Main Sequence•Red Giant•Core Helium-Burning•Double Shell-Burning•Planetary Nebula•White Dwarf
Double Shell Burning
•Star moves up and right on H-R diagram
•Molecular Cloud•Protostar•Main Sequence•Red Giant•Core Helium-Burning•Double Shell-Burning•Planetary Nebula•White Dwarf
Core Helium-Burning
Double Shell-Burning
Giant Stages – Mass dependance•For stars from 0.5 to 3 MSun, it is qualitatively the same
•Heavy stars do everything faster•For heavier stars, some details are different
•Higher temperature and lower density•Core isn’t so compact•No dramatic increase in luminosity
•Motion on the H-R diagram is mostly horizontal
•Stars get bigger and cooler, not brighter
•Molecular Cloud•Protostar•Main Sequence•Red Giant•Core Helium-Burning•Double Shell-Burning•Planetary Nebula•White Dwarf
•Molecular Cloud•Protostar•Main Sequence•Red Giant•Core Helium-Burning•Double Shell-Burning•Planetary Nebula•White Dwarf
Giant Stages – Mass dependance
•Molecular Cloud•Protostar•Main Sequence•Red Giant•Core Helium-Burning•Double Shell-Burning•Planetary Nebula•White Dwarf
Giant Stages – Mass Dependence
Core Helium-Burning
•Molecular Cloud•Protostar•Main Sequence•Red Giant•Core Helium-Burning•Double Shell-Burning•Planetary Nebula•White Dwarf
Giant Stages – Mass Dependence
Double Shell-Burning
Core Helium Burning
Mass Loss•During Red Giant and especially Double Shell-Burning stage, star is huge and luminous
•Gravity is weak at the surface•Dust particles form on surface
•These absorb light very efficiently•Light pressure begins pushing surface away
•Like solar wind, but much stronger•Star begins to quickly lose substantial mass•The inside is hardly affected, for a while
•Hydrogen Helium Carbon/Oxygen
•Molecular Cloud•Protostar•Main Sequence•Red Giant•Core Helium-Burning•Double Shell-Burning•Planetary Nebula•White Dwarf