PX158 - I6c - evolution of a sun-like star

*dotted lines represent short timespans

• $1\to 2:H\to He$ fusion in the core

  • most of the sun's life

• $2\to 3:$ red giant phase

  • $H$ depleted in the core
  • $H$ starts to fuse in a shell around the core

• $3\to 4:$ horizontal branch phase

  • $T\sim {10}^{8}K$ in the core
  • $He$ starts to fuse in the core into $C/O$
  • reaction $\propto T^{40}$

• $4\to 5:$ asymptotic giant branch (AGB)

  • $He$ depleted in the core
  • the core is $C/O$
  • $He$ fusion in a shell around the core
  • $H$ fusion in a shell around the $He$ shell

• $5\to 6:$ the star's envelope is lost to space, forming a planetary nebula (PN)

  • white dwarf: $C/O$ with a thin atmosphere of $He/H$
  • $M_{WD}\approx 0.6M_{\odot }$