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)

http://antwrp.gsfc.nasa.gov/apod/ap011217.html

It’s expanding!

For years, the key to the Crab Nebula was there is plain sight

In 1968 the breakthrough came