the deaths of stars
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0. The Deaths of Stars. Chapter 10. 0. Mass Transfer in Binary Stars. In a binary system, each star controls a finite region of space, bounded by the Roche Lobes (or Roche surfaces). - PowerPoint PPT PresentationTRANSCRIPT
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The Deaths of Stars
Chapter 10
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Mass Transfer in Binary StarsIn a binary system, each star controls a finite region of space,
bounded by the Roche Lobes (or Roche surfaces).
Lagrange points = points of stability, where matter can
remain without being pulled towards one of the stars.
Matter can flow over from one star to another through the Inner Lagrange Point L1.
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Recycled Stellar Evolution
Mass transfer in a binary system can significantly
alter the stars’ masses and affect their stellar evolution.
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White Dwarfs in Binary SystemsBinary consisting of WD + MS or Red Giant star => WD accretes matter from
the companion
Angular momentum conservation => accreted
matter forms a disk, called accretion disk
Matter in the accretion disk heats up to ~ 1 million K => X-ray emission => “X-ray binary”
T ~ 106 K
X-ray emission
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Nova Explosions
Nova Cygni 1975
Hydrogen accreted through the accretion
disk accumulates on the surface of the WD.
Very hot, dense layer of non-fusing hydrogen
on the WD surface
Explosive onset of H fusion
Nova explosion
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Recurrent NovaeIn many cases, the mass transfer
cycle resumes after a nova explosion.
→ Cycle of repeating explosions every few years – decades
T Pyxidis
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The Fate of our Sunand the End of Earth
• The Sun will expand to a Red giant in ~ 5 billion years.
• Expands to ~ Earth’s radius• Earth will then be
incinerated!• Sun may form a planetary
nebula (but uncertain)• Sun’s C,O core will become
a white dwarf
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The Deaths of Massive Stars: Supernovae
Final stages of fusion in high-mass
stars (> 8 Msun), leading to the
formation of an Iron core, happen
extremely rapidly: Si burning lasts only for ~ 1 day
Iron core ultimately collapses, triggering an explosion that destroys
the star:
A Supernova
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Numerical Simulations of
Supernova Explosions
The details of supernova
explosions are highly complex and not quite
understood yet.
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Supernova Remnants
The Cygnus Loop
The Veil Nebula
The Crab Nebula:
Remnant of a supernova observed
in a.d. 1054
Cassiopeia AOptical
X-rays