Download Foundation 1 - Discovering Astronomy

Chapters 14 and 15
Stellar Evolution and Stellar Remnants
Star Birth: Nebula
Young star: Protostar
Adult: Main Sequence
As the temperature in the interior rises, nuclear
reactions produce outward force and balances
the inward force of gravity  hydrostatic
equilibrium = star becomes stable and
contraction stopsmain-sequence star
Energy Sources in Stars
• 4 hydrogen nuclei fuse to
become 1 helium nucleus
• Since the mass of 4 hydrogen
nuclei is greater than the mass
of 1 helium nucleus, the
leftover mass (0.7%) is
converted to energy by
Einstein’s equation: E=mc2
The end states of stars depends
upon its mass!
The more massive a star, the
faster it consumes its fuel, the
shorter its lifetime
A
B
C
Evolution of Low Mass Stars
including our Sun
M < 10 Solar Masses
Old Age: Red Giant
Elderly, core:
White Dwarf
The core of
the
white dwarf
star is
now all carbon
and
oxygen
Elderly, envelope:
Planetary nebula
Ring Nebula
Eskimo Nebula
Yeah, but what about the
really Massive stars?
Old Age: Red Supergiant
Figure 13.19
Elderly, dying star:
Supernova
Super Nova Remnants
Our Sun will never explode.
Only massive stars explode
as supernova!
Elderly, core:
Neutron Star
Core
High mass stars
becomes so dense that
protons and electrons
combine to become
neutrons and star
becomes neutron star
Life Cycle of a Low Mass Star
Life Cycle of a High Mass Star