Transcript The Evolution of Massive Stars

The Evolution of Massive Stars
The Fate of 10, 20, or 30 solar
mass stars
Eta Carinae:
possibly a
100 solar
mass star:
what will it
do next?
The Evolution of massive stars
picks up where low mass
stellar evolution ends…the
C,O core continues to contract
In innermost core,
successively hotter
nuclear reactions
generate heavier nuclei
as “ashes” until Iron.
This is the peak of the
“curve of binding
energy”
Following iron synthesis, “core
collapse” occurs
Prediction of core collapse:
generation of a Neutron Star
Process of
neutronization:
e+p > n + nu
A ball of neutrons the size
of Iowa City with the mass
of the Sun
The Neutron Star
This is the end
product of a truly
massive star
Predicted Consequences of
Massive Star Evolution
• Huge explosion: 10**44 Joules = total
energy radiated by the Sun in its lifetime
• Pulse of neutrinos as core collapses
• “Pollution” of the interstellar medium as
explosion blows off the outer stellar core
• Birth of the “neutron star”
Prediction #1: Huge explosion =
supernova
Simulated
appearance of
the supernova
of 1006
AD…between
crescent moon
and Venus in
brightness for a
few weeks
The most recent visible
supernova: SN1987A
“burst” of neutrinos observed at beginning of supernova explosion
“Feature” #3: “Pollution” of the
Interstellar Medium
Cassiopeia A:
expanding cloud
of “metal-rich”
debris from a
supernova in
about 1680:
today the
brightest radio
source in the sky
Where is Cas A?
An
interstellar
dark cloud
in front of
it
prevented a
spectacle at
the time of
the Royal
Society
Neutron Stars: do they exist?
An object with the
mass of the Sun
crammed into a ball
this big
The end product of
massive star
evolution
Neutron Stars: a brief history
• Basic physics understood in the 1930s
• At that time, no known counterparts
• In the 1950s and 1960s, more and more
strange objects found, but where were the
neutrons stars, or did they even exist?
• The case of the Crab Nebula (supernova of
1054 AD)
The Crab Nebula (M1)
It’s
expand
ing!
http://antwrp.gsfc.nasa.gov/apod/ap011217.html
For years, the key to the Crab
Nebula was there is plain sight
In 1968 the breakthrough came