The Discovery of the Neutron Star

The Neutron Predicted by Ernest Rutherford in 1920 Experimentally discovered by James Chadwick in 1932

The Neutron Star Fritz Zwicky and Walter Baade mathematically predicted the existence of a neutron star in 1934.

Massive Star Life Cycle

The Discovery of the Pulsar Jocelyn Bell discovers the first pulsating star (pulsar for short) using a radio telescope in The star pulsed once every 1.3 seconds.

Pulsars and Their Relation to Neutron Stars By 1968, with the discovery of the Crab and Vela pulsars in Supernova Remnants, MOST scientists believed that pulsars were in fact neutron stars. Crab Pulsar in the Crab nebula

How do Neutron Stars Form

What is a pulsar? A pulsar is a rapidly rotating neutron star that beam radio waves towards Earth. This brings up some new questions...  What is a neutron star?  Why is it rotating?  Why is it beaming radio waves?

Life of a Massive Star Stars spend most of their lives fusing hydrogen into helium The star is literally blowing itself apart while gravity tries to crush it When a star runs out of hydrogen it tries to fuse heavier elements

Death of a Massive Star No energy can be extracted by fusing iron Without a source of energy, what do you think will happen to the star? Watch and see: DnhkM3I

Supernovae 1. Gravity causes the outer layers to collapse at super-sonic speeds 2. When outer layers hit the Iron core, they pile up and “bounce back” 3. Most of the star explodes

A Neutron Star is Born The star's core is left behind and goes through a wild transformation What was once a core of Iron is now a super- dense neutron star Write and equation to represent what is happening here.

Electron Capture (inverse Beta decay) Beta Decay Process

Neutron Star Facts – Diameter, Mass, Temperature and Rotation 1.4 times as massive as our Sun (500,000 Earth masses – 40% more massive than our Sun) About 12 miles across 1 teaspoon would weigh 5.5 billion tons 10 million ºF at birth Some spin several times a second or faster Why do neutron stars spin?

The more massive the Progenitor Star – the smaller the Remnant Stellar Remnant – Size Comparisons

Neutron Star: Mass and Diameter 1.4 times as massive as our Sun (500,000 Earth masses – 40% more massive than our Sun) About 12 miles across Calculate the density of a neutron star Density = Mass/Volume

Density Extremely dense objects – 100,000,000,000,000,000 kg m -3 – Next thing down from a black hole

Your weight

Calculate your weight on a neutron star applet

Neutron star properties Extremely rapid spin – Rotation rates in excess of 700 Hz – Speed at surface ~ significant fraction of c

Neutron Star Facts Neutron stars can also highly magnetized – Fields thousands – billions times stronger than the strongest man made magnets This has an amazing effect – Neutron stars can emit beams of radio waves

Do You See a Pulsar? Pulsars are like interstellar lighthouses If the beam points towards Earth, we see a pulse of radio waves

Sounds of Pulsars

What did you notice?

Pulsar Recycling Some pulsars spin faster than others – When the pulsar period is a few milliseconds, we call it a millisecond pulsar MSPs are actually recycled pulsars and are the most exciting kinds

Pulsar Recycling Some pulsars spin faster than others – When the pulsar period is a few milliseconds, we call it a millisecond pulsar MSPs are actually recycled pulsars and are the most exciting kinds

Millisecond Pulsars