Chapter Twenty/Twenty-One

Questions for the Day• What are the end states of stars?

• How do stars interact?

What are the end states of stars?

• When nuclear fuel is exhausted, hydrostatic equilibrium is upset causing the star to collapse.

• Depending on the amount of material the stars will end up as:– White Dwarfs (< 1.5M)– Neutron Stars/Black Holes (1.5M)

Hydrostatic Equilibrium

A Nova

Mass-Radius Relationship White Dwarfs

Evolution of White Dwarfs

Supernova in NGC 4725

Stellar Evolution: Supernova

Light Curve of a Supernova

Supernova 1987a

Cassiopeia A

Crab Nebula

Mass – Luminosity of Neutron Stars

Joycelyn Bell Burnell• 1943 – • Born in Belfast, Ireland• Grew up in the

countryside and studied physics and astronomy

• Graduated Cambridge Univsersity in England

Nobel Prize Women in Science, Sharon Bertsch McGrayne, Citadel Press, 1993

Jocelyn Bell Burnell’s Work• Worked under Anthony Hewish at the 2.5

acre radio telescope at Cambridge• Studied object that varied in the radio with

the telescope.• Hewish and Burnell discovered an object

that varied on a time scale of 1.3 seconds.• Hewish won Nobel prize in 1974 for the

discovery of Pulsars.

Radio Signal from CP 1919

Diagram of Pulsar

A Black Hole

How do interact?• Star interact by creating binary or

multiple star systems.• Types of Binary Stars:

– Visual: One can observe the two stars using a telescope.

– Spectroscopic: One can use spectroscopy to observe the stars.

– Eclipsing: One can use light curves to observe the stars.

Appearance of Curved Spacetime

Light in Black Hole

Spectroscopy of Binary Stars

Spectroscopy of Binary Stars

Visual versus Spectroscopic

Light Curves of Binary Stars

Various Binary Stars

Star Light Program From Dan Bruton

Roche Lobes of Binary Stars

Black Hole and Star

Homework 9• Explain why two main differences

between neutron stars and white dwarfs occur.

• Page 492, CQ 3, 9, 24• Page 517, CQ 8, 15