PowerPoint Presentation

The Discovery of the Neutron Star

The Neutron

Predicted by Ernest Rutherford in 1920Experimentally discovered by James Chadwick in 1932The 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 1967. 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 nebulaHow 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?8Life of a Massive StarStars spend most of their lives fusing hydrogen into heliumThe 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

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11Death of a Massive StarNo energy can be extracted by fusing ironWithout a source of energy, what do you think will happen to the star?

Watch and see:http://www.youtube.com/watch?v=p8HcDnhkM3I 12Supernovae Gravity causes the outer layers to collapse at super-sonic speeds When outer layers hit the Iron core, they pile up and bounce back Most of the star explodes

13A Neutron Star is BornThe star's core is left behind and goes through a wild transformationWhat was once a core of Iron is now a super-dense neutron star

Write and equation to represent what is happening here.14Electron Capture (inverse Beta decay)

Beta Decay Process

Neutron Star Facts Diameter, Mass, Temperature and Rotation1.4 times as massive as our Sun (500,000 Earth masses 40% more massive than our Sun)About 12 miles across1 teaspoon would weigh 5.5 billion tons10 million F at birthSome spin several times a second or fasterWhy do neutron stars spin?16

The more massive the Progenitor Star the smaller the RemnantStellar Remnant Size ComparisonsNeutron Star: Mass and Diameter1.4 times as massive as our Sun (500,000 Earth masses 40% more massive than our Sun)

About 12 miles acrossCalculate the density of a neutron starDensity = Mass/Volume

DensityExtremely dense objects100,000,000,000,000,000 kg m-3Next thing down from a black hole

24Your weight

Calculate your weight on a neutron starapplethttp://www.exploratorium.edu/ronh/weight/ Neutron star propertiesExtremely rapid spinRotation rates in excess of 700 HzSpeed at surface ~ significant fraction of c

27Neutron Star FactsNeutron stars can also highly magnetizedFields thousands billions times stronger than the strongest man made magnetsThis has an amazing effectNeutron stars can emit beams of radio waves28

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Do You See a Pulsar?Pulsars are like interstellar lighthousesIf the beam points towards Earth, we see a pulse of radio waves30

Sounds of Pulsars

VelaSpins 11 times every secondB1937+21Spins 714 times every second

B0329+54Spins 1.4 times every second

32What did you notice?33Pulsar RecyclingSome pulsars spin faster than othersWhen the pulsar period is a few milliseconds, we call it a millisecond pulsarMSPs are actually recycled pulsars and are the most exciting kinds34Pulsar RecyclingSome pulsars spin faster than othersWhen the pulsar period is a few milliseconds, we call it a millisecond pulsarMSPs are actually recycled pulsars and are the most exciting kinds35

Millisecond Pulsars36