Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download When the Sun Dies—12 Oct Composition of the sun
Document related concepts
Astronomical unit wikipedia , lookup
History of Solar System formation and evolution hypotheses wikipedia , lookup
Aquarius (constellation) wikipedia , lookup
Dyson sphere wikipedia , lookup
Tropical year wikipedia , lookup
Formation and evolution of the Solar System wikipedia , lookup
Timeline of astronomy wikipedia , lookup
Transcript
When the Sun Dies—12 Oct Composition of the sun • • Sun will use up the hydrogen in the center in 5Byr • Center of sun must shrink to get hotter to balance gravity In center, hydrogen is half used up. 1H 4He – Sun will become a red giant. Surface expands. • Sun will become a planetary nebula • Sun will become a white dwarf 3He×100 Sun as a main-sequence star Sun as a subgiant • H is gone in the core • The never-ending battle between gravity and pressure. How does the sun adjust? Radius photosphere ç Temperature HèHe burning core Inert H • Without burning fuel to keep temperature up, pressure (PV=nRT) would fall and gravity would win. • Core shrinks, gets hotter • H? He in the a shell surrounding inert core • Balance restored. Luminosity è • H? He in the core • T=15MK • Fuel will last another 5 Byr. Luminosity è 5 Byr from now Radius photosphere ç Temperature Inert He core HèHe burning shell Inert H 1 • Without burning fuel to keep temperature up, pressure (PV=nRT) would fall and gravity would win. • Core shrinks, gets hotter • H? He in the a shell surrounding inert core • Balance restored. A few 100Myr later • H is gone in the core • The never-ending battle between gravity and pressure. How does the sun adjust? Radius photosphere ç Temperature Inert He core HèHe burning shell Inert H • Inert He core expands • Without burning fuel to keep temperature up, pressure (PV=nRT) would fall and gravity would win. • Core shrinks, gets hotter T=200MK • 3He? C in the core (triple alpha process) • Balance restored. Luminosity è Sun Burns HeliumLater • H is gone in the core & shell is exhausted • The never-ending battle between gravity and pressure. How does the sun adjust? Sun as a giant Luminosity è • H is gone in the core • The never-ending battle between gravity and pressure. How does the sun adjust? Luminosity è Sun as a giant Later Radius photosphere • Without burning fuel to keep temperature up, pressure (PV=nRT) would fall and gravity would win. • Core shrinks, gets hotter • H? He in the a shell surrounding inert core • Balance restored. ç Temperature Inert He core HèHe burning shell Inert H • Inert He core expands Other fusion reactions? • Sun has one more trick after He is exhausted in core. Radius photosphere • Burn He in a shell ç Temperature He èC in core HèHe burning shell Inert H • Sun is not massive enough to shrink further and get hotter • Core is supported by pressure of degenerate electrons. • Temperature does not rise to burn anything else. • End of the road: planetary nebula & white dwarf core Reaction Tri ple -al pha pro cesMin. s Temp. 4 1H è 4He 10 MK 3 4He è 12C 200 MK 12C + 4He è 16O, Ne, Na, 800 MK Mg Ne è O, Mg 1500MK O è Mg, S 2000MK Si èFe peak 3000MK 2 Summarizing question • At what point will the earth die? 3
