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 •Molecular Cloud •Protostar •Main Sequence •Red Giant •Core Helium- Burning •Double Shell- Giant Stages – Low Mass Stars
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
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
•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